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All questions of Single-Phase Induction Motors for Electrical Engineering (EE) Exam
Which type of load is offered by cranes and hoists ?- a)Gradually varying load
- b)Non-reversing, no-load start
- c)Reversing, light start
- d)Reversing, heavy start
Correct answer is option 'D'. Can you explain this answer?
Which type of load is offered by cranes and hoists ?
a)
Gradually varying load
b)
Non-reversing, no-load start
c)
Reversing, light start
d)
Reversing, heavy start
|
Siddhesh Pardhiye answered |
As when desending the lift or when crane is dropping wieght from a high height to low hieght . They requires torque is opposite direction to maintain or limit the speed of crane or hoist. As well as they require high starting torque to suddenly pick up the heavy load while uplifting from bottom to a specific hieght .
So option D
So option D
In a ceilingfan employing capacitor run motor- a)secondary winding surrounds the primary winding
- b)primary winding surrounds the secondary winding
- c)both are usual arrangements
- d)none of the above
Correct answer is option 'A'. Can you explain this answer?
In a ceilingfan employing capacitor run motor
a)
secondary winding surrounds the primary winding
b)
primary winding surrounds the secondary winding
c)
both are usual arrangements
d)
none of the above
|
Anoushka Kumar answered |
Ceiling Fan Employing Capacitor Run Motor:
A ceiling fan employing a capacitor run motor is a type of single-phase induction motor that is widely used in ceiling fans. It has a stator with a main winding and an auxiliary winding, and a rotor with a squirrel-cage. The main winding is connected directly to the AC power supply, while the auxiliary winding is connected in series with a capacitor. The capacitor is used to create a phase shift between the current flowing through the main winding and the current flowing through the auxiliary winding.
Secondary Winding Surrounds the Primary Winding:
In a ceiling fan employing capacitor run motor, the secondary winding surrounds the primary winding. This means that the auxiliary winding, which is connected in series with the capacitor, is wound around the main winding, which is directly connected to the AC power supply. The purpose of this arrangement is to create a magnetic field that rotates around the stator, which in turn causes the rotor to rotate.
Advantages of Capacitor Run Motors:
Capacitor run motors have several advantages over other types of single-phase induction motors, including:
1. High starting torque: Capacitor run motors have a higher starting torque than other types of single-phase motors, which makes them ideal for use in ceiling fans.
2. Low noise: Capacitor run motors produce less noise than other types of single-phase motors, which makes them ideal for use in residential and commercial buildings.
3. Energy efficient: Capacitor run motors are more energy efficient than other types of single-phase motors, which makes them ideal for use in appliances that require continuous operation, such as ceiling fans.
Conclusion:
In summary, a ceiling fan employing capacitor run motor has a secondary winding that surrounds the primary winding. This arrangement creates a magnetic field that rotates around the stator, which in turn causes the rotor to rotate. Capacitor run motors have several advantages over other types of single-phase induction motors, including high starting torque, low noise, and energy efficiency.
A ceiling fan employing a capacitor run motor is a type of single-phase induction motor that is widely used in ceiling fans. It has a stator with a main winding and an auxiliary winding, and a rotor with a squirrel-cage. The main winding is connected directly to the AC power supply, while the auxiliary winding is connected in series with a capacitor. The capacitor is used to create a phase shift between the current flowing through the main winding and the current flowing through the auxiliary winding.
Secondary Winding Surrounds the Primary Winding:
In a ceiling fan employing capacitor run motor, the secondary winding surrounds the primary winding. This means that the auxiliary winding, which is connected in series with the capacitor, is wound around the main winding, which is directly connected to the AC power supply. The purpose of this arrangement is to create a magnetic field that rotates around the stator, which in turn causes the rotor to rotate.
Advantages of Capacitor Run Motors:
Capacitor run motors have several advantages over other types of single-phase induction motors, including:
1. High starting torque: Capacitor run motors have a higher starting torque than other types of single-phase motors, which makes them ideal for use in ceiling fans.
2. Low noise: Capacitor run motors produce less noise than other types of single-phase motors, which makes them ideal for use in residential and commercial buildings.
3. Energy efficient: Capacitor run motors are more energy efficient than other types of single-phase motors, which makes them ideal for use in appliances that require continuous operation, such as ceiling fans.
Conclusion:
In summary, a ceiling fan employing capacitor run motor has a secondary winding that surrounds the primary winding. This arrangement creates a magnetic field that rotates around the stator, which in turn causes the rotor to rotate. Capacitor run motors have several advantages over other types of single-phase induction motors, including high starting torque, low noise, and energy efficiency.
In a split phase motor- a)the starting winding is connected through a centrifugal switch
- b)the running winding is connected through a centrifugal switch
- c)both starting and running windings are connected through a centrifugal switch
- d)centrifugal switch is used to control supply voltage
Correct answer is option 'A'. Can you explain this answer?
In a split phase motor
a)
the starting winding is connected through a centrifugal switch
b)
the running winding is connected through a centrifugal switch
c)
both starting and running windings are connected through a centrifugal switch
d)
centrifugal switch is used to control supply voltage
|
Hridoy Chakraborty answered |
Split Phase Motor and Centrifugal Switch
Split phase motors are single-phase induction motors that have two windings - a starting winding and a running winding. These windings are placed at right angles to each other and are connected to the main winding of the motor. The starting winding has more turns, and it is also smaller in size than the running winding.
Centrifugal switch is an electro-mechanical device that is used to open or close an electrical circuit based on the rotational speed of a shaft or rotor. In split phase motors, a centrifugal switch is used to disconnect the starting winding from the power supply once the motor has reached a certain speed.
Answer Explanation
The correct option is 'A' - the starting winding is connected through a centrifugal switch.
When a split phase motor is started, both the starting and running windings are energized. The starting winding produces a magnetic field that is shifted by 90 degrees from the magnetic field produced by the running winding. This results in a rotating magnetic field that causes the rotor to start rotating.
Once the motor has reached around 70-80% of its rated speed, the centrifugal switch opens and disconnects the starting winding from the power supply. This is necessary because if the starting winding remains energized, it will produce a magnetic field that will interfere with the magnetic field produced by the running winding. This will cause the motor to overheat and eventually fail.
Therefore, the centrifugal switch is used to prevent this from happening by disconnecting the starting winding once the motor is up to speed. The running winding then takes over and continues to produce the rotating magnetic field that drives the motor.
In summary, the correct option is 'A' because the centrifugal switch is used to connect and disconnect the starting winding from the power supply in a split phase motor.
Split phase motors are single-phase induction motors that have two windings - a starting winding and a running winding. These windings are placed at right angles to each other and are connected to the main winding of the motor. The starting winding has more turns, and it is also smaller in size than the running winding.
Centrifugal switch is an electro-mechanical device that is used to open or close an electrical circuit based on the rotational speed of a shaft or rotor. In split phase motors, a centrifugal switch is used to disconnect the starting winding from the power supply once the motor has reached a certain speed.
Answer Explanation
The correct option is 'A' - the starting winding is connected through a centrifugal switch.
When a split phase motor is started, both the starting and running windings are energized. The starting winding produces a magnetic field that is shifted by 90 degrees from the magnetic field produced by the running winding. This results in a rotating magnetic field that causes the rotor to start rotating.
Once the motor has reached around 70-80% of its rated speed, the centrifugal switch opens and disconnects the starting winding from the power supply. This is necessary because if the starting winding remains energized, it will produce a magnetic field that will interfere with the magnetic field produced by the running winding. This will cause the motor to overheat and eventually fail.
Therefore, the centrifugal switch is used to prevent this from happening by disconnecting the starting winding once the motor is up to speed. The running winding then takes over and continues to produce the rotating magnetic field that drives the motor.
In summary, the correct option is 'A' because the centrifugal switch is used to connect and disconnect the starting winding from the power supply in a split phase motor.
In a hysteresis motor, the rotor must have- a)retentivity
- b)resistivity
- c)susceptibility
- d)none of the above
Correct answer is option 'A'. Can you explain this answer?
In a hysteresis motor, the rotor must have
a)
retentivity
b)
resistivity
c)
susceptibility
d)
none of the above
|
Ritika Sarkar answered |
Hysteresis motor is a type of synchronous motor that operates by the principle of hysteresis loss. The rotor of this motor is made up of a ferromagnetic material with high retentivity, which means it can retain a large amount of magnetism even in the absence of an external magnetic field.
Explanation:
• Retentivity is a characteristic of a magnetic material that determines the amount of magnetism it can retain. In hysteresis motor, the rotor must have high retentivity so that it can maintain a strong magnetic field even in the absence of an external magnetic field.
• The stator of the hysteresis motor produces a rotating magnetic field, which induces a magnetic field in the rotor. Due to the high retentivity of the rotor material, the induced magnetic field in the rotor lags behind the rotating magnetic field of the stator.
• This lagging causes the rotor to rotate in the direction of the rotating magnetic field of the stator. The hysteresis motor does not require any external excitation, and it operates on the principle of hysteresis loss.
• The rotor of the hysteresis motor also requires low resistivity to reduce the power loss due to eddy currents. However, susceptibility is not a relevant characteristic for the hysteresis motor rotor.
Conclusion:
Therefore, from the above explanation, we can conclude that in a hysteresis motor, the rotor must have high retentivity to maintain a strong magnetic field even in the absence of an external magnetic field.
Explanation:
• Retentivity is a characteristic of a magnetic material that determines the amount of magnetism it can retain. In hysteresis motor, the rotor must have high retentivity so that it can maintain a strong magnetic field even in the absence of an external magnetic field.
• The stator of the hysteresis motor produces a rotating magnetic field, which induces a magnetic field in the rotor. Due to the high retentivity of the rotor material, the induced magnetic field in the rotor lags behind the rotating magnetic field of the stator.
• This lagging causes the rotor to rotate in the direction of the rotating magnetic field of the stator. The hysteresis motor does not require any external excitation, and it operates on the principle of hysteresis loss.
• The rotor of the hysteresis motor also requires low resistivity to reduce the power loss due to eddy currents. However, susceptibility is not a relevant characteristic for the hysteresis motor rotor.
Conclusion:
Therefore, from the above explanation, we can conclude that in a hysteresis motor, the rotor must have high retentivity to maintain a strong magnetic field even in the absence of an external magnetic field.
If a D.C. series motor is operated on A.C. supply, it will- a)spark excessively
- b)have poor efficiency
- c)have poor power factor
- d)all of the above
Correct answer is option 'D'. Can you explain this answer?
If a D.C. series motor is operated on A.C. supply, it will
a)
spark excessively
b)
have poor efficiency
c)
have poor power factor
d)
all of the above
|
Rithika Pillai answered |
DC series motor is designed to operate on DC supply. However, if it is connected to an AC supply, several issues can arise, leading to excessive sparking, poor efficiency, and poor power factor. Let's understand each of these points in detail:
1. Excessive Sparking:
When a DC series motor is operated on AC supply, the commutation process becomes challenging. In a DC motor, commutation is the process of reversing the current in the armature coil at the appropriate timing to maintain rotation. This reversal of current is achieved by using a commutator and brushes.
In an AC supply, the current continuously changes direction, which leads to sparking between the brushes and the commutator segments. This excessive sparking not only causes damage to the commutator and brushes but also leads to increased wear and tear of the motor components.
2. Poor Efficiency:
Efficiency is defined as the ratio of output power to input power. When a DC series motor is operated on AC supply, it experiences various losses that reduce its overall efficiency. Some of the major losses in this case include:
- Iron losses: AC supply results in increased hysteresis and eddy current losses in the motor's iron core, leading to reduced efficiency.
- Brush losses: The sparking between the brushes and commutator causes additional resistive losses, reducing the motor's efficiency.
- Copper losses: The AC supply induces additional losses due to skin effect and proximity effect in the motor's winding, further reducing the efficiency.
Overall, these losses in the motor result in poor efficiency, meaning that a significant portion of the input power is wasted as losses instead of being converted into useful mechanical work.
3. Poor Power Factor:
Power factor is a measure of how effectively the motor utilizes the electrical power supplied to it. It is the cosine of the phase angle between the voltage and current waveforms. In an AC system, the power factor can be lagging or leading, depending on the nature of the load.
When a DC series motor is connected to an AC supply, it causes a lagging power factor. This is because the motor draws a highly non-sinusoidal current, which is rich in harmonics. These harmonics distort the current waveform and result in a lag between the voltage and current, leading to a poor power factor.
Therefore, when a DC series motor is operated on AC supply, it exhibits excessive sparking, poor efficiency, and poor power factor. These issues can significantly affect the motor's performance and lifespan. It is always recommended to use a DC supply for DC series motors to ensure optimal operation.
1. Excessive Sparking:
When a DC series motor is operated on AC supply, the commutation process becomes challenging. In a DC motor, commutation is the process of reversing the current in the armature coil at the appropriate timing to maintain rotation. This reversal of current is achieved by using a commutator and brushes.
In an AC supply, the current continuously changes direction, which leads to sparking between the brushes and the commutator segments. This excessive sparking not only causes damage to the commutator and brushes but also leads to increased wear and tear of the motor components.
2. Poor Efficiency:
Efficiency is defined as the ratio of output power to input power. When a DC series motor is operated on AC supply, it experiences various losses that reduce its overall efficiency. Some of the major losses in this case include:
- Iron losses: AC supply results in increased hysteresis and eddy current losses in the motor's iron core, leading to reduced efficiency.
- Brush losses: The sparking between the brushes and commutator causes additional resistive losses, reducing the motor's efficiency.
- Copper losses: The AC supply induces additional losses due to skin effect and proximity effect in the motor's winding, further reducing the efficiency.
Overall, these losses in the motor result in poor efficiency, meaning that a significant portion of the input power is wasted as losses instead of being converted into useful mechanical work.
3. Poor Power Factor:
Power factor is a measure of how effectively the motor utilizes the electrical power supplied to it. It is the cosine of the phase angle between the voltage and current waveforms. In an AC system, the power factor can be lagging or leading, depending on the nature of the load.
When a DC series motor is connected to an AC supply, it causes a lagging power factor. This is because the motor draws a highly non-sinusoidal current, which is rich in harmonics. These harmonics distort the current waveform and result in a lag between the voltage and current, leading to a poor power factor.
Therefore, when a DC series motor is operated on AC supply, it exhibits excessive sparking, poor efficiency, and poor power factor. These issues can significantly affect the motor's performance and lifespan. It is always recommended to use a DC supply for DC series motors to ensure optimal operation.
If the centrifugal switch does not open at 70 to 80 percent of synchronous speed of motor, it would result in- a)Damage to the starting winding
- b)Damage to the centrifugal switch
- c)Overloading of running winding
- d)None of the above
Correct answer is option 'A'. Can you explain this answer?
If the centrifugal switch does not open at 70 to 80 percent of synchronous speed of motor, it would result in
a)
Damage to the starting winding
b)
Damage to the centrifugal switch
c)
Overloading of running winding
d)
None of the above
|
Sravya Khanna answered |
Damage to the starting winding
Opening of the centrifugal switch at the correct speed is crucial for the safe operation of a motor. If the centrifugal switch fails to open at 70 to 80 percent of synchronous speed, it can lead to damage to the starting winding. Here's how:
- Role of centrifugal switch: The centrifugal switch is responsible for disconnecting the starting winding of the motor once it reaches a certain speed. This is essential to prevent the starting winding from being continuously powered during normal operation.
- Impact of not opening: If the centrifugal switch does not open at the specified speed, the starting winding will remain energized even when the motor is running at higher speeds. This can result in overheating of the starting winding due to excessive current flow, leading to insulation damage and ultimately failure of the winding.
- Consequences: Damage to the starting winding can significantly reduce the efficiency and lifespan of the motor. It can also cause the motor to draw more current than intended, potentially leading to overheating and other electrical faults.
Therefore, it is important for the centrifugal switch to open at the correct speed to ensure the safe and reliable operation of the motor, preventing damage to the starting winding and other components.
Opening of the centrifugal switch at the correct speed is crucial for the safe operation of a motor. If the centrifugal switch fails to open at 70 to 80 percent of synchronous speed, it can lead to damage to the starting winding. Here's how:
- Role of centrifugal switch: The centrifugal switch is responsible for disconnecting the starting winding of the motor once it reaches a certain speed. This is essential to prevent the starting winding from being continuously powered during normal operation.
- Impact of not opening: If the centrifugal switch does not open at the specified speed, the starting winding will remain energized even when the motor is running at higher speeds. This can result in overheating of the starting winding due to excessive current flow, leading to insulation damage and ultimately failure of the winding.
- Consequences: Damage to the starting winding can significantly reduce the efficiency and lifespan of the motor. It can also cause the motor to draw more current than intended, potentially leading to overheating and other electrical faults.
Therefore, it is important for the centrifugal switch to open at the correct speed to ensure the safe and reliable operation of the motor, preventing damage to the starting winding and other components.
Which of the following motors is used in mixies ?- a)Repulsion motor
- b)Reluctance motor
- c)Hysteresis motor
- d)Universal motor
Correct answer is option 'D'. Can you explain this answer?
Which of the following motors is used in mixies ?
a)
Repulsion motor
b)
Reluctance motor
c)
Hysteresis motor
d)
Universal motor
|
|
Prasad Verma answered |
**Explanation:**
Mixies, also known as mixer grinders, are kitchen appliances used for grinding and blending purposes. They typically consist of a motor and a set of rotating blades or jars.
The motor used in mixies is a **universal motor**.
**Universal Motor:**
A universal motor is a type of electric motor that can operate on both AC and DC power. It is a series-wound motor, meaning that the field winding and the armature winding are connected in series. This allows the motor to have high starting torque and variable speed control.
**Advantages of Universal Motors:**
- High starting torque: The universal motor is capable of delivering high starting torque, which is necessary for grinding and blending applications.
- Variable speed control: The speed of the motor can be easily controlled by varying the input voltage or by using a speed controller. This is important in mixies as different ingredients require different speeds for effective grinding.
- Compact size: Universal motors are compact in size, making them suitable for use in small kitchen appliances like mixies.
- Cost-effective: Universal motors are relatively inexpensive compared to other types of motors, making them a popular choice for mixies and similar appliances.
**Other Motor Options:**
- **Repulsion Motor:** Repulsion motors are generally used in applications where high starting torque is required, such as in elevators and hoists. However, they are not commonly used in mixies.
- **Reluctance Motor:** Reluctance motors are primarily used in applications requiring high torque at low speeds, such as in industrial machines. They are not commonly used in mixies.
- **Hysteresis Motor:** Hysteresis motors are synchronous motors that operate based on hysteresis losses in the rotor. They are typically used in applications requiring smooth and constant speed, such as in clocks and record players. They are not commonly used in mixies.
Therefore, the correct answer is option **D) Universal Motor**, as it is the most suitable motor for mixies due to its high starting torque, variable speed control, compact size, and cost-effectiveness.
Mixies, also known as mixer grinders, are kitchen appliances used for grinding and blending purposes. They typically consist of a motor and a set of rotating blades or jars.
The motor used in mixies is a **universal motor**.
**Universal Motor:**
A universal motor is a type of electric motor that can operate on both AC and DC power. It is a series-wound motor, meaning that the field winding and the armature winding are connected in series. This allows the motor to have high starting torque and variable speed control.
**Advantages of Universal Motors:**
- High starting torque: The universal motor is capable of delivering high starting torque, which is necessary for grinding and blending applications.
- Variable speed control: The speed of the motor can be easily controlled by varying the input voltage or by using a speed controller. This is important in mixies as different ingredients require different speeds for effective grinding.
- Compact size: Universal motors are compact in size, making them suitable for use in small kitchen appliances like mixies.
- Cost-effective: Universal motors are relatively inexpensive compared to other types of motors, making them a popular choice for mixies and similar appliances.
**Other Motor Options:**
- **Repulsion Motor:** Repulsion motors are generally used in applications where high starting torque is required, such as in elevators and hoists. However, they are not commonly used in mixies.
- **Reluctance Motor:** Reluctance motors are primarily used in applications requiring high torque at low speeds, such as in industrial machines. They are not commonly used in mixies.
- **Hysteresis Motor:** Hysteresis motors are synchronous motors that operate based on hysteresis losses in the rotor. They are typically used in applications requiring smooth and constant speed, such as in clocks and record players. They are not commonly used in mixies.
Therefore, the correct answer is option **D) Universal Motor**, as it is the most suitable motor for mixies due to its high starting torque, variable speed control, compact size, and cost-effectiveness.
Single phase induction motor usually operates on- a)0.6 power factor lagging
- b)0.8 power factor lagging
- c)0.8 power factor leading
- d)unity power factor
Correct answer is option 'A'. Can you explain this answer?
Single phase induction motor usually operates on
a)
0.6 power factor lagging
b)
0.8 power factor lagging
c)
0.8 power factor leading
d)
unity power factor
|
Gargi Basak answered |
Single Phase Induction Motor Operating Power Factor
Single phase induction motors typically operate with a power factor lagging, specifically around 0.6.
Explanation
Power Factor Lagging
- Power factor lagging indicates that the current lags behind the voltage in an AC circuit.
- In single phase induction motors, the power factor is usually less than 1 due to the presence of magnetizing and core loss components in the motor.
- The power factor of 0.6 indicates that the current lags significantly behind the voltage, leading to a less efficient operation of the motor.
Importance of Power Factor
- Power factor is crucial in determining the efficiency of electrical systems.
- Low power factor in motors can result in increased energy consumption, leading to higher electricity bills.
- Maintaining a power factor close to unity (1) is desirable to ensure efficient operation of electrical equipment.
Operating Conditions
- Single phase induction motors are commonly used in household appliances, fans, pumps, and other small applications.
- These motors are designed to operate efficiently with a power factor lagging around 0.6 under normal operating conditions.
In conclusion, single phase induction motors typically operate with a power factor lagging around 0.6, which is considered standard for these types of motors. Understanding the power factor and its impact on motor efficiency is essential for maintaining optimal performance and reducing energy consumption in electrical systems.
Single phase induction motors typically operate with a power factor lagging, specifically around 0.6.
Explanation
Power Factor Lagging
- Power factor lagging indicates that the current lags behind the voltage in an AC circuit.
- In single phase induction motors, the power factor is usually less than 1 due to the presence of magnetizing and core loss components in the motor.
- The power factor of 0.6 indicates that the current lags significantly behind the voltage, leading to a less efficient operation of the motor.
Importance of Power Factor
- Power factor is crucial in determining the efficiency of electrical systems.
- Low power factor in motors can result in increased energy consumption, leading to higher electricity bills.
- Maintaining a power factor close to unity (1) is desirable to ensure efficient operation of electrical equipment.
Operating Conditions
- Single phase induction motors are commonly used in household appliances, fans, pumps, and other small applications.
- These motors are designed to operate efficiently with a power factor lagging around 0.6 under normal operating conditions.
In conclusion, single phase induction motors typically operate with a power factor lagging around 0.6, which is considered standard for these types of motors. Understanding the power factor and its impact on motor efficiency is essential for maintaining optimal performance and reducing energy consumption in electrical systems.
In a capacitor start single-phase motor, when capacitor is replaced by a resistance- a)torque will increase
- b)the motor will consume less power
- c)motor will run in reverse direction
- d)motor will continue to run in same direction
Correct answer is option 'D'. Can you explain this answer?
In a capacitor start single-phase motor, when capacitor is replaced by a resistance
a)
torque will increase
b)
the motor will consume less power
c)
motor will run in reverse direction
d)
motor will continue to run in same direction
|
Samarth Khanna answered |
Capacitor Start Single-Phase Motor
A capacitor start single-phase motor is a type of motor that is used in many applications. It is commonly used in household appliances, such as air conditioners and refrigerators. This type of motor uses a capacitor to start the motor and then switches to a different type of winding to keep the motor running.
Replacing Capacitor with Resistance
When the capacitor in a capacitor start single-phase motor is replaced by a resistance, several things happen. The following are some of the effects of replacing the capacitor with a resistance:
1. Torque will decrease
The torque produced by the motor will decrease when the capacitor is replaced by a resistance. This is because the capacitor provides a higher starting torque than a resistance.
2. Power consumption will increase
When the capacitor is replaced by a resistance, the power consumption of the motor will increase. This is because the motor will have to work harder to produce the same amount of torque.
3. Motor will run in the same direction
The motor will continue to run in the same direction when the capacitor is replaced by a resistance. This is because the direction of rotation is determined by the winding of the motor, not by the capacitor.
Conclusion
In conclusion, when the capacitor in a capacitor start single-phase motor is replaced by a resistance, the torque produced by the motor will decrease, the power consumption of the motor will increase, and the motor will continue to run in the same direction. It is important to note that replacing the capacitor with a resistance is not recommended, as it can cause damage to the motor and reduce its lifespan.
A capacitor start single-phase motor is a type of motor that is used in many applications. It is commonly used in household appliances, such as air conditioners and refrigerators. This type of motor uses a capacitor to start the motor and then switches to a different type of winding to keep the motor running.
Replacing Capacitor with Resistance
When the capacitor in a capacitor start single-phase motor is replaced by a resistance, several things happen. The following are some of the effects of replacing the capacitor with a resistance:
1. Torque will decrease
The torque produced by the motor will decrease when the capacitor is replaced by a resistance. This is because the capacitor provides a higher starting torque than a resistance.
2. Power consumption will increase
When the capacitor is replaced by a resistance, the power consumption of the motor will increase. This is because the motor will have to work harder to produce the same amount of torque.
3. Motor will run in the same direction
The motor will continue to run in the same direction when the capacitor is replaced by a resistance. This is because the direction of rotation is determined by the winding of the motor, not by the capacitor.
Conclusion
In conclusion, when the capacitor in a capacitor start single-phase motor is replaced by a resistance, the torque produced by the motor will decrease, the power consumption of the motor will increase, and the motor will continue to run in the same direction. It is important to note that replacing the capacitor with a resistance is not recommended, as it can cause damage to the motor and reduce its lifespan.
A single-phase induction motor is- a)inherently self-starting with high torque
- b)inherently self-starting with low torque
- c)inherently non-self-starting with low torque
- d)inherently non-self-starting with high torque
Correct answer is option 'C'. Can you explain this answer?
A single-phase induction motor is
a)
inherently self-starting with high torque
b)
inherently self-starting with low torque
c)
inherently non-self-starting with low torque
d)
inherently non-self-starting with high torque
|
Uday Saini answered |
Introduction
A single-phase induction motor is a type of electric motor that is widely used in various applications. It is commonly used for powering household appliances, fans, pumps, and small industrial machinery. One of the important characteristics of an induction motor is its ability to start and provide torque to drive the load.
Explanation
The correct answer to the question is option 'C', which states that a single-phase induction motor is inherently non-self-starting with low torque. This means that a single-phase induction motor requires some external means to start and does not have the ability to start on its own. Additionally, it provides relatively low torque during the starting process compared to other types of motors.
Reasons for being inherently non-self-starting
There are several reasons why a single-phase induction motor is inherently non-self-starting:
1. Lack of rotating magnetic field: Unlike three-phase induction motors, which have a rotating magnetic field that induces currents in the rotor, a single-phase induction motor only has a single-phase power supply. This results in a pulsating magnetic field that does not produce enough torque to start the motor.
2. Starting winding: In order to overcome the lack of a rotating magnetic field, single-phase induction motors are typically equipped with a starting winding. This winding is connected in series with the main winding and is displaced from it by an electrical angle of 90 degrees. The starting winding creates an artificial rotating magnetic field that induces currents in the rotor, allowing the motor to start.
3. Capacitor: In addition to the starting winding, a single-phase induction motor may also require a capacitor to assist in the starting process. The capacitor helps to create a phase shift between the currents in the starting winding and the main winding, further enhancing the production of a rotating magnetic field.
4. Low starting torque: Despite the presence of a starting winding and capacitor, a single-phase induction motor still provides relatively low starting torque compared to other types of motors. This is due to the pulsating nature of the magnetic field and the inherent asymmetry of the single-phase power supply.
Conclusion
In conclusion, a single-phase induction motor is inherently non-self-starting with low torque. It requires external means such as a starting winding and capacitor to overcome the lack of a rotating magnetic field and provide sufficient torque to start the motor. Understanding these characteristics is important for properly selecting and operating single-phase induction motors in various applications.
A single-phase induction motor is a type of electric motor that is widely used in various applications. It is commonly used for powering household appliances, fans, pumps, and small industrial machinery. One of the important characteristics of an induction motor is its ability to start and provide torque to drive the load.
Explanation
The correct answer to the question is option 'C', which states that a single-phase induction motor is inherently non-self-starting with low torque. This means that a single-phase induction motor requires some external means to start and does not have the ability to start on its own. Additionally, it provides relatively low torque during the starting process compared to other types of motors.
Reasons for being inherently non-self-starting
There are several reasons why a single-phase induction motor is inherently non-self-starting:
1. Lack of rotating magnetic field: Unlike three-phase induction motors, which have a rotating magnetic field that induces currents in the rotor, a single-phase induction motor only has a single-phase power supply. This results in a pulsating magnetic field that does not produce enough torque to start the motor.
2. Starting winding: In order to overcome the lack of a rotating magnetic field, single-phase induction motors are typically equipped with a starting winding. This winding is connected in series with the main winding and is displaced from it by an electrical angle of 90 degrees. The starting winding creates an artificial rotating magnetic field that induces currents in the rotor, allowing the motor to start.
3. Capacitor: In addition to the starting winding, a single-phase induction motor may also require a capacitor to assist in the starting process. The capacitor helps to create a phase shift between the currents in the starting winding and the main winding, further enhancing the production of a rotating magnetic field.
4. Low starting torque: Despite the presence of a starting winding and capacitor, a single-phase induction motor still provides relatively low starting torque compared to other types of motors. This is due to the pulsating nature of the magnetic field and the inherent asymmetry of the single-phase power supply.
Conclusion
In conclusion, a single-phase induction motor is inherently non-self-starting with low torque. It requires external means such as a starting winding and capacitor to overcome the lack of a rotating magnetic field and provide sufficient torque to start the motor. Understanding these characteristics is important for properly selecting and operating single-phase induction motors in various applications.
Which of the following motors is preferred for tape-recorders?- a)Shaded pole motor
- b)Hysteresis motor
- c)Two value capacitor motor
- d)Universal motor
Correct answer is option 'B'. Can you explain this answer?
Which of the following motors is preferred for tape-recorders?
a)
Shaded pole motor
b)
Hysteresis motor
c)
Two value capacitor motor
d)
Universal motor
|
Yashvi Shah answered |
Preferred Motor for Tape-Recorders
Hysteresis Motor
A hysteresis motor is the preferred motor for tape-recorders. This is because of the following reasons:
- Speed Stability: Hysteresis motor provides stable speed, which is crucial for tape-recorders to maintain the correct tape speed and prevent distortion of the recorded audio.
- Low Noise: Hysteresis motors operate silently, which is desirable for tape-recorders to reduce unwanted noise in the recorded audio.
- High Torque: Hysteresis motors have high starting torque, which is important for tape-recorders to quickly start and stop the tape movement.
- Low Maintenance: Hysteresis motors have a simple design and do not require frequent maintenance, which is desirable for tape-recorders to reduce downtime.
Other Motor Types
- Shaded Pole Motor: Shaded pole motors are commonly used in small appliances and fans. They have low starting torque and poor speed stability, which make them unsuitable for tape-recorders.
- Two Value Capacitor Motor: Two value capacitor motors are commonly used in washing machines and air conditioners. They have high starting torque but poor speed stability, which make them unsuitable for tape-recorders.
- Universal Motor: Universal motors are commonly used in power tools and vacuum cleaners. They have high starting torque and variable speed, but they are noisy and require frequent maintenance, which make them unsuitable for tape-recorders.
Therefore, a hysteresis motor is the most suitable motor for tape-recorders due to its stable speed, low noise, high torque, and low maintenance.
Hysteresis Motor
A hysteresis motor is the preferred motor for tape-recorders. This is because of the following reasons:
- Speed Stability: Hysteresis motor provides stable speed, which is crucial for tape-recorders to maintain the correct tape speed and prevent distortion of the recorded audio.
- Low Noise: Hysteresis motors operate silently, which is desirable for tape-recorders to reduce unwanted noise in the recorded audio.
- High Torque: Hysteresis motors have high starting torque, which is important for tape-recorders to quickly start and stop the tape movement.
- Low Maintenance: Hysteresis motors have a simple design and do not require frequent maintenance, which is desirable for tape-recorders to reduce downtime.
Other Motor Types
- Shaded Pole Motor: Shaded pole motors are commonly used in small appliances and fans. They have low starting torque and poor speed stability, which make them unsuitable for tape-recorders.
- Two Value Capacitor Motor: Two value capacitor motors are commonly used in washing machines and air conditioners. They have high starting torque but poor speed stability, which make them unsuitable for tape-recorders.
- Universal Motor: Universal motors are commonly used in power tools and vacuum cleaners. They have high starting torque and variable speed, but they are noisy and require frequent maintenance, which make them unsuitable for tape-recorders.
Therefore, a hysteresis motor is the most suitable motor for tape-recorders due to its stable speed, low noise, high torque, and low maintenance.
The value of starting capacitor of a fractional horse power motor will be- a)100 uF
- b)200 uF
- c)300 uF
- d)400 uF
Correct answer is option 'C'. Can you explain this answer?
The value of starting capacitor of a fractional horse power motor will be
a)
100 uF
b)
200 uF
c)
300 uF
d)
400 uF
|
Poulomi Ahuja answered |
Starting Capacitor for Fractional Horse Power Motor
Starting capacitor is an essential component of a single-phase fractional horse power (FHP) motor. It is used to provide the necessary starting torque to the motor so that it can overcome the inertia and start rotating.
Factors Affecting Starting Capacitor Value
The value of the starting capacitor for a FHP motor depends on several factors, including the:
- Type of motor
- Rated voltage and frequency
- Power rating (in watts or horsepower)
- Load conditions
- Ambient temperature
In general, the starting capacitor value for a FHP motor is chosen based on a standard range of capacitance values that are suitable for most applications.
Value of Starting Capacitor for FHP Motor
Option 'C' (300 uF) is the correct answer for this question. However, it should be noted that the actual value of the starting capacitor for a FHP motor depends on the specific motor and application requirements.
In general, the starting capacitor value for a FHP motor can range from 50 uF to 400 uF, depending on the factors mentioned above. Higher values of capacitance provide more starting torque, but may also increase the risk of overloading or damaging the motor.
Conclusion
Choosing the right starting capacitor value for a FHP motor requires careful consideration of various factors. It is important to consult the manufacturer's specifications and guidelines, as well as to perform appropriate testing and adjustments to ensure optimal performance and reliability of the motor.
Starting capacitor is an essential component of a single-phase fractional horse power (FHP) motor. It is used to provide the necessary starting torque to the motor so that it can overcome the inertia and start rotating.
Factors Affecting Starting Capacitor Value
The value of the starting capacitor for a FHP motor depends on several factors, including the:
- Type of motor
- Rated voltage and frequency
- Power rating (in watts or horsepower)
- Load conditions
- Ambient temperature
In general, the starting capacitor value for a FHP motor is chosen based on a standard range of capacitance values that are suitable for most applications.
Value of Starting Capacitor for FHP Motor
Option 'C' (300 uF) is the correct answer for this question. However, it should be noted that the actual value of the starting capacitor for a FHP motor depends on the specific motor and application requirements.
In general, the starting capacitor value for a FHP motor can range from 50 uF to 400 uF, depending on the factors mentioned above. Higher values of capacitance provide more starting torque, but may also increase the risk of overloading or damaging the motor.
Conclusion
Choosing the right starting capacitor value for a FHP motor requires careful consideration of various factors. It is important to consult the manufacturer's specifications and guidelines, as well as to perform appropriate testing and adjustments to ensure optimal performance and reliability of the motor.
Two-value capacitor motor finds increased application as compressor motor in small home air-conditioners because- a)it is comparatively cheaper
- b)it has almost non-destructible capacitor
- c)it has low starting as well as running currents at relatively high power factor
- d)it is quiet in operation
Correct answer is option 'C'. Can you explain this answer?
Two-value capacitor motor finds increased application as compressor motor in small home air-conditioners because
a)
it is comparatively cheaper
b)
it has almost non-destructible capacitor
c)
it has low starting as well as running currents at relatively high power factor
d)
it is quiet in operation
|
Abhishek Chauhan answered |
Explanation:
The two-value capacitor motor finds increased application as a compressor motor in small home air-conditioners because of the following reasons:
Low Starting and Running Currents:
- The two-value capacitor motor has low starting and running currents, which means it consumes less power during operation.
- This is beneficial for small home air-conditioners as they have limited power availability and lower power consumption helps in reducing energy costs.
Relatively High Power Factor:
- The power factor is a measure of how effectively the motor converts electrical power into mechanical power.
- The two-value capacitor motor has a relatively high power factor, meaning it is more efficient in converting electrical power to mechanical power.
- This efficiency is important for compressor motors in air-conditioners as it helps in reducing energy losses and improving overall system performance.
Cost-Effectiveness:
- The two-value capacitor motor is comparatively cheaper compared to other types of compressor motors.
- This cost-effectiveness makes it a preferred choice for small home air-conditioners, where affordability is an important factor.
Durability:
- The two-value capacitor motor is known for its durability and long lifespan.
- The capacitor used in this motor is non-destructible, meaning it has a longer operating life compared to other types of capacitors.
- This durability is important for compressor motors in air-conditioners as they are subjected to continuous operation and need to withstand various environmental conditions.
Quiet Operation:
- The two-value capacitor motor operates quietly, producing less noise compared to other types of motors.
- This is beneficial for small home air-conditioners as they are usually installed in living spaces where noise reduction is important for user comfort.
In conclusion, the two-value capacitor motor is preferred as a compressor motor in small home air-conditioners due to its low starting and running currents, relatively high power factor, cost-effectiveness, durability, and quiet operation. These factors contribute to improved energy efficiency, reduced costs, and enhanced user comfort, making it an ideal choice for small home air-conditioners.
The two-value capacitor motor finds increased application as a compressor motor in small home air-conditioners because of the following reasons:
Low Starting and Running Currents:
- The two-value capacitor motor has low starting and running currents, which means it consumes less power during operation.
- This is beneficial for small home air-conditioners as they have limited power availability and lower power consumption helps in reducing energy costs.
Relatively High Power Factor:
- The power factor is a measure of how effectively the motor converts electrical power into mechanical power.
- The two-value capacitor motor has a relatively high power factor, meaning it is more efficient in converting electrical power to mechanical power.
- This efficiency is important for compressor motors in air-conditioners as it helps in reducing energy losses and improving overall system performance.
Cost-Effectiveness:
- The two-value capacitor motor is comparatively cheaper compared to other types of compressor motors.
- This cost-effectiveness makes it a preferred choice for small home air-conditioners, where affordability is an important factor.
Durability:
- The two-value capacitor motor is known for its durability and long lifespan.
- The capacitor used in this motor is non-destructible, meaning it has a longer operating life compared to other types of capacitors.
- This durability is important for compressor motors in air-conditioners as they are subjected to continuous operation and need to withstand various environmental conditions.
Quiet Operation:
- The two-value capacitor motor operates quietly, producing less noise compared to other types of motors.
- This is beneficial for small home air-conditioners as they are usually installed in living spaces where noise reduction is important for user comfort.
In conclusion, the two-value capacitor motor is preferred as a compressor motor in small home air-conditioners due to its low starting and running currents, relatively high power factor, cost-effectiveness, durability, and quiet operation. These factors contribute to improved energy efficiency, reduced costs, and enhanced user comfort, making it an ideal choice for small home air-conditioners.
Speed torque characteristic of a repulsion induction motor is similar to that of a D.C.- a)shunt motor
- b)series motor
- c)compound motor
- d)separately excited motor
Correct answer is option 'C'. Can you explain this answer?
Speed torque characteristic of a repulsion induction motor is similar to that of a D.C.
a)
shunt motor
b)
series motor
c)
compound motor
d)
separately excited motor
|
Meghana Gupta answered |
The speed-torque characteristic of a repulsion induction motor is similar to that of a compound motor (option C). Let's understand why this is the case.
1. Introduction to Repulsion Induction Motor:
- A repulsion induction motor is a type of single-phase AC motor that combines the features of both a repulsion motor and an induction motor.
- It consists of a stator (stationary part) and a rotor (rotating part).
- The stator windings are similar to those of an induction motor, while the rotor windings are similar to those of a DC motor.
2. Speed-Torque Characteristics:
- The speed-torque characteristic of a motor describes the relationship between the motor's output torque and its rotational speed.
- A motor's torque is the rotational force it generates, and speed is the rate at which it rotates.
3. Compound Motor:
- A compound motor is a type of DC motor that has both series and shunt field windings.
- The series winding is connected in series with the armature, while the shunt winding is connected in parallel to the armature.
- The compound motor combines the high starting torque of a series motor and the steady-state speed regulation of a shunt motor.
4. Similarities between Repulsion Induction Motor and Compound Motor:
- Both the repulsion induction motor and the compound motor exhibit similar speed-torque characteristics.
- The torque-speed curve of a compound motor is similar to that of a repulsion induction motor.
- This is because both motors have a combination of series and shunt winding characteristics.
- The series winding in both motors provides high starting torque, while the shunt winding helps regulate the speed.
5. Differences between Repulsion Induction Motor and Compound Motor:
- The major difference between these motors is their power supply. The repulsion induction motor is powered by single-phase AC, while the compound motor is powered by DC.
- The construction and operation of these motors also differ significantly.
In conclusion, the speed-torque characteristic of a repulsion induction motor is similar to that of a compound motor. Both motors exhibit a combination of series and shunt winding characteristics, providing high starting torque and good speed regulation. However, it is important to note that the repulsion induction motor operates on single-phase AC, while the compound motor operates on DC.
1. Introduction to Repulsion Induction Motor:
- A repulsion induction motor is a type of single-phase AC motor that combines the features of both a repulsion motor and an induction motor.
- It consists of a stator (stationary part) and a rotor (rotating part).
- The stator windings are similar to those of an induction motor, while the rotor windings are similar to those of a DC motor.
2. Speed-Torque Characteristics:
- The speed-torque characteristic of a motor describes the relationship between the motor's output torque and its rotational speed.
- A motor's torque is the rotational force it generates, and speed is the rate at which it rotates.
3. Compound Motor:
- A compound motor is a type of DC motor that has both series and shunt field windings.
- The series winding is connected in series with the armature, while the shunt winding is connected in parallel to the armature.
- The compound motor combines the high starting torque of a series motor and the steady-state speed regulation of a shunt motor.
4. Similarities between Repulsion Induction Motor and Compound Motor:
- Both the repulsion induction motor and the compound motor exhibit similar speed-torque characteristics.
- The torque-speed curve of a compound motor is similar to that of a repulsion induction motor.
- This is because both motors have a combination of series and shunt winding characteristics.
- The series winding in both motors provides high starting torque, while the shunt winding helps regulate the speed.
5. Differences between Repulsion Induction Motor and Compound Motor:
- The major difference between these motors is their power supply. The repulsion induction motor is powered by single-phase AC, while the compound motor is powered by DC.
- The construction and operation of these motors also differ significantly.
In conclusion, the speed-torque characteristic of a repulsion induction motor is similar to that of a compound motor. Both motors exhibit a combination of series and shunt winding characteristics, providing high starting torque and good speed regulation. However, it is important to note that the repulsion induction motor operates on single-phase AC, while the compound motor operates on DC.
In a two value capacitor motor, the capacitor used for running purposes is- a)air capacitor
- b)paper spaced oil filled type
- c)ceramic type
- d)a.c. electrolytic type
Correct answer is option 'B'. Can you explain this answer?
In a two value capacitor motor, the capacitor used for running purposes is
a)
air capacitor
b)
paper spaced oil filled type
c)
ceramic type
d)
a.c. electrolytic type
|
|
Ankita Das answered |
Capacitor Motor:
A two-value capacitor motor is a type of single-phase induction motor that has two capacitors, one for starting and the other for running purposes. This type of motor is used in many applications, including fans, pumps, and compressors.
Types of Capacitors Used in Two-Value Capacitor Motors:
There are different types of capacitors that can be used in a two-value capacitor motor. Some of the commonly used capacitors are:
1. Air Capacitor:
An air capacitor is a type of capacitor that uses air as the dielectric material. This type of capacitor is not commonly used in two-value capacitor motors.
2. Paper Spaced Oil Filled Type:
A paper spaced oil-filled capacitor is a type of capacitor that uses paper as the dielectric material and oil as the insulating medium. This type of capacitor is commonly used in two-value capacitor motors.
3. Ceramic Type:
A ceramic capacitor is a type of capacitor that uses ceramic as the dielectric material. This type of capacitor is not commonly used in two-value capacitor motors.
4. A.C. Electrolytic Type:
An AC electrolytic capacitor is a type of capacitor that uses an electrolyte as the dielectric material. This type of capacitor is not commonly used in two-value capacitor motors.
Conclusion:
In conclusion, the capacitor used for running purposes in a two-value capacitor motor is a paper spaced oil-filled type capacitor. This type of capacitor provides high capacitance and low leakage current, making it ideal for use in single-phase induction motors.
A two-value capacitor motor is a type of single-phase induction motor that has two capacitors, one for starting and the other for running purposes. This type of motor is used in many applications, including fans, pumps, and compressors.
Types of Capacitors Used in Two-Value Capacitor Motors:
There are different types of capacitors that can be used in a two-value capacitor motor. Some of the commonly used capacitors are:
1. Air Capacitor:
An air capacitor is a type of capacitor that uses air as the dielectric material. This type of capacitor is not commonly used in two-value capacitor motors.
2. Paper Spaced Oil Filled Type:
A paper spaced oil-filled capacitor is a type of capacitor that uses paper as the dielectric material and oil as the insulating medium. This type of capacitor is commonly used in two-value capacitor motors.
3. Ceramic Type:
A ceramic capacitor is a type of capacitor that uses ceramic as the dielectric material. This type of capacitor is not commonly used in two-value capacitor motors.
4. A.C. Electrolytic Type:
An AC electrolytic capacitor is a type of capacitor that uses an electrolyte as the dielectric material. This type of capacitor is not commonly used in two-value capacitor motors.
Conclusion:
In conclusion, the capacitor used for running purposes in a two-value capacitor motor is a paper spaced oil-filled type capacitor. This type of capacitor provides high capacitance and low leakage current, making it ideal for use in single-phase induction motors.
A.C. series motor as compared to D.C. series motor has- a)smaller brush width
- b)less number of field turns
- c)more number of armature turns
- d)less air gap
- e)all of the above
Correct answer is option 'E'. Can you explain this answer?
A.C. series motor as compared to D.C. series motor has
a)
smaller brush width
b)
less number of field turns
c)
more number of armature turns
d)
less air gap
e)
all of the above
|
Subham Chaudhary answered |
A.C. series motor and D.C. series motor are both types of electric motors that are used for various applications. However, there are certain differences between the two types of motors. Let's discuss each option to understand why the correct answer is option 'E' - all of the above.
- Smaller brush width:
In a D.C. series motor, the brushes are typically wider compared to an A.C. series motor. The wider brush width helps to distribute the current more evenly and reduce the risk of arcing. On the other hand, the smaller brush width in an A.C. series motor allows for better commutation and reduces the chances of sparking and brush wear.
- Less number of field turns:
The field turns in a motor refer to the number of turns of wire in the field winding. In a D.C. series motor, the field turns are generally higher compared to an A.C. series motor. This is because D.C. series motors require a higher magnetic field strength to generate the required torque and speed. In contrast, A.C. series motors operate at higher frequencies and can achieve the required magnetic field strength with fewer field turns.
- More number of armature turns:
The armature turns in a motor refer to the number of turns of wire in the armature winding. In an A.C. series motor, the armature turns are typically higher compared to a D.C. series motor. This is because A.C. series motors operate at higher frequencies and require more armature turns to generate the necessary torque and speed. The higher number of armature turns also helps in reducing the armature resistance and increasing the motor's efficiency.
- Less air gap:
The air gap in a motor refers to the distance between the rotor and the stator. In an A.C. series motor, the air gap is generally smaller compared to a D.C. series motor. This is because A.C. series motors operate at higher frequencies, and a smaller air gap helps to reduce the magnetic reluctance and improve the motor's performance.
In conclusion, all of the given options are correct. A.C. series motors have a smaller brush width, less number of field turns, more number of armature turns, and a smaller air gap compared to D.C. series motors. These differences arise due to the different operating principles and requirements of the two types of motors.
- Smaller brush width:
In a D.C. series motor, the brushes are typically wider compared to an A.C. series motor. The wider brush width helps to distribute the current more evenly and reduce the risk of arcing. On the other hand, the smaller brush width in an A.C. series motor allows for better commutation and reduces the chances of sparking and brush wear.
- Less number of field turns:
The field turns in a motor refer to the number of turns of wire in the field winding. In a D.C. series motor, the field turns are generally higher compared to an A.C. series motor. This is because D.C. series motors require a higher magnetic field strength to generate the required torque and speed. In contrast, A.C. series motors operate at higher frequencies and can achieve the required magnetic field strength with fewer field turns.
- More number of armature turns:
The armature turns in a motor refer to the number of turns of wire in the armature winding. In an A.C. series motor, the armature turns are typically higher compared to a D.C. series motor. This is because A.C. series motors operate at higher frequencies and require more armature turns to generate the necessary torque and speed. The higher number of armature turns also helps in reducing the armature resistance and increasing the motor's efficiency.
- Less air gap:
The air gap in a motor refers to the distance between the rotor and the stator. In an A.C. series motor, the air gap is generally smaller compared to a D.C. series motor. This is because A.C. series motors operate at higher frequencies, and a smaller air gap helps to reduce the magnetic reluctance and improve the motor's performance.
In conclusion, all of the given options are correct. A.C. series motors have a smaller brush width, less number of field turns, more number of armature turns, and a smaller air gap compared to D.C. series motors. These differences arise due to the different operating principles and requirements of the two types of motors.
A schrage motor can run on- a)zero slip
- b)negative slip
- c)positive slip
- d)all of the above
Correct answer is option 'D'. Can you explain this answer?
A schrage motor can run on
a)
zero slip
b)
negative slip
c)
positive slip
d)
all of the above
|
|
Om Saini answered |
Introduction:
A schrage motor is a type of motor that operates with a slip, which is the difference between the synchronous speed and the actual speed of the motor. The slip can be either positive, negative, or zero, depending on the operating conditions. In a schrage motor, the slip can vary and the motor can run on all three types of slips.
Explanation:
A schrage motor is designed to operate with a variable slip. It is a type of induction motor that can run at speeds above or below the synchronous speed. The slip is defined as the difference between the synchronous speed and the actual speed of the motor. The synchronous speed is determined by the frequency of the power supply and the number of poles in the motor.
Zero Slip:
Zero slip occurs when the actual speed of the motor is equal to the synchronous speed. In this case, the rotor is rotating at the same speed as the stator's rotating magnetic field. The motor operates at its maximum efficiency and delivers its rated power. A schrage motor can run on zero slip when the load torque is equal to the developed torque.
Negative Slip:
Negative slip occurs when the actual speed of the motor is higher than the synchronous speed. This situation arises when the motor is over-excited or when the load torque is less than the developed torque. In this case, the rotor rotates faster than the stator's rotating magnetic field. The motor acts as a generator and feeds power back into the system. Negative slip operation is not common and is usually not desired unless the motor is specifically designed for regenerative braking.
Positive Slip:
Positive slip occurs when the actual speed of the motor is lower than the synchronous speed. This situation occurs when the load torque is higher than the developed torque. In this case, the rotor rotates slower than the stator's rotating magnetic field. The motor operates in a motoring mode and delivers torque to the load. Positive slip operation is the most common mode of operation for a schrage motor.
Conclusion:
In conclusion, a schrage motor can run on zero slip, negative slip, and positive slip. The slip depends on the operating conditions, load torque, and developed torque. A schrage motor is designed to operate with a variable slip, allowing it to provide efficient operation and a wide range of speed control.
A schrage motor is a type of motor that operates with a slip, which is the difference between the synchronous speed and the actual speed of the motor. The slip can be either positive, negative, or zero, depending on the operating conditions. In a schrage motor, the slip can vary and the motor can run on all three types of slips.
Explanation:
A schrage motor is designed to operate with a variable slip. It is a type of induction motor that can run at speeds above or below the synchronous speed. The slip is defined as the difference between the synchronous speed and the actual speed of the motor. The synchronous speed is determined by the frequency of the power supply and the number of poles in the motor.
Zero Slip:
Zero slip occurs when the actual speed of the motor is equal to the synchronous speed. In this case, the rotor is rotating at the same speed as the stator's rotating magnetic field. The motor operates at its maximum efficiency and delivers its rated power. A schrage motor can run on zero slip when the load torque is equal to the developed torque.
Negative Slip:
Negative slip occurs when the actual speed of the motor is higher than the synchronous speed. This situation arises when the motor is over-excited or when the load torque is less than the developed torque. In this case, the rotor rotates faster than the stator's rotating magnetic field. The motor acts as a generator and feeds power back into the system. Negative slip operation is not common and is usually not desired unless the motor is specifically designed for regenerative braking.
Positive Slip:
Positive slip occurs when the actual speed of the motor is lower than the synchronous speed. This situation occurs when the load torque is higher than the developed torque. In this case, the rotor rotates slower than the stator's rotating magnetic field. The motor operates in a motoring mode and delivers torque to the load. Positive slip operation is the most common mode of operation for a schrage motor.
Conclusion:
In conclusion, a schrage motor can run on zero slip, negative slip, and positive slip. The slip depends on the operating conditions, load torque, and developed torque. A schrage motor is designed to operate with a variable slip, allowing it to provide efficient operation and a wide range of speed control.
Which of the following motors will operate at high power factor ?- a)Shaped pole motor
- b)Split phase motor
- c)Capacitor start motor
- d)Capacitor run motor
Correct answer is option 'D'. Can you explain this answer?
Which of the following motors will operate at high power factor ?
a)
Shaped pole motor
b)
Split phase motor
c)
Capacitor start motor
d)
Capacitor run motor
|
|
Anoushka Choudhury answered |
Introduction:
In electrical engineering, power factor is a measure of how effectively a device converts electrical power into useful work. A high power factor indicates that a device is operating efficiently and effectively utilizing the electrical power supplied to it. In the case of motors, a high power factor is desirable as it reduces the amount of reactive power required from the electrical system.
Explanation:
Among the given options, the capacitor run motor is the one that operates at a high power factor. This is due to the presence of a capacitor in the motor circuit, which helps to improve the power factor.
Capacitor Run Motor:
A capacitor run motor is a type of single-phase induction motor that has a capacitor connected in series with the auxiliary winding. The capacitor provides a leading current to the auxiliary winding, which helps to improve the power factor of the motor.
Working Principle:
When the motor is initially started, the capacitor is connected in series with the auxiliary winding. This creates a phase difference between the main winding current and the auxiliary winding current, resulting in a rotating magnetic field. Once the motor reaches a certain speed, a centrifugal switch disconnects the capacitor from the circuit, and the motor continues to run on the main winding alone.
Advantages of Capacitor Run Motor:
1. High Power Factor: The presence of the capacitor in the circuit helps to improve the power factor of the motor, resulting in efficient operation.
2. High Efficiency: The improved power factor leads to reduced losses and increased efficiency of the motor.
3. Higher Starting Torque: The auxiliary winding and capacitor arrangement provide a higher starting torque compared to other types of single-phase motors.
Conclusion:
In summary, the capacitor run motor is the type of motor that operates at a high power factor. The presence of a capacitor in the circuit helps to improve the power factor, resulting in efficient operation and reduced reactive power demand from the electrical system.
In electrical engineering, power factor is a measure of how effectively a device converts electrical power into useful work. A high power factor indicates that a device is operating efficiently and effectively utilizing the electrical power supplied to it. In the case of motors, a high power factor is desirable as it reduces the amount of reactive power required from the electrical system.
Explanation:
Among the given options, the capacitor run motor is the one that operates at a high power factor. This is due to the presence of a capacitor in the motor circuit, which helps to improve the power factor.
Capacitor Run Motor:
A capacitor run motor is a type of single-phase induction motor that has a capacitor connected in series with the auxiliary winding. The capacitor provides a leading current to the auxiliary winding, which helps to improve the power factor of the motor.
Working Principle:
When the motor is initially started, the capacitor is connected in series with the auxiliary winding. This creates a phase difference between the main winding current and the auxiliary winding current, resulting in a rotating magnetic field. Once the motor reaches a certain speed, a centrifugal switch disconnects the capacitor from the circuit, and the motor continues to run on the main winding alone.
Advantages of Capacitor Run Motor:
1. High Power Factor: The presence of the capacitor in the circuit helps to improve the power factor of the motor, resulting in efficient operation.
2. High Efficiency: The improved power factor leads to reduced losses and increased efficiency of the motor.
3. Higher Starting Torque: The auxiliary winding and capacitor arrangement provide a higher starting torque compared to other types of single-phase motors.
Conclusion:
In summary, the capacitor run motor is the type of motor that operates at a high power factor. The presence of a capacitor in the circuit helps to improve the power factor, resulting in efficient operation and reduced reactive power demand from the electrical system.
A hysteresis motor works on the principle of- a)hysteresis loss
- b)magnetisation of rotor
- c)eddy current loss
- d)electromagnetic induction
Correct answer is option 'A'. Can you explain this answer?
A hysteresis motor works on the principle of
a)
hysteresis loss
b)
magnetisation of rotor
c)
eddy current loss
d)
electromagnetic induction
|
|
Niharika Basu answered |
Hysteresis Motor Principle
The hysteresis motor is a synchronous motor that operates on the principle of hysteresis loss. It is a type of single-phase motor that uses a rotor made of a ferromagnetic material. The motor is designed to produce a rotating magnetic field by using a stator winding that is fed with a single-phase AC supply. The rotor rotates at the same speed as the rotating magnetic field.
Hysteresis Loss
Hysteresis loss is a type of energy loss that occurs in ferromagnetic materials when they are subjected to a varying magnetic field. This loss is due to the resistance of the material to changes in the direction of its magnetization. The loss results in the generation of heat, which can be detrimental to the performance of the motor.
Working of Hysteresis Motor
The hysteresis motor works by exploiting the hysteresis loss in the rotor. The rotor is made of a ferromagnetic material that is highly resistive to changes in the direction of its magnetization. When the stator winding is energized with a single-phase AC supply, a rotating magnetic field is produced. This magnetic field induces a magnetic field in the rotor, causing it to rotate.
The rotor rotates at the same speed as the rotating magnetic field due to the hysteresis loss in the rotor. The hysteresis loss causes the rotor to lag behind the rotating magnetic field, resulting in a torque being produced on the rotor. This torque causes the rotor to rotate at the same speed as the rotating magnetic field.
Advantages of Hysteresis Motor
- The hysteresis motor is highly efficient and has a high power factor.
- It has a simple construction and is easy to maintain.
- The motor operates quietly and is vibration-free.
- The motor has a high starting torque and can be used in applications where high starting torque is required.
Disadvantages of Hysteresis Motor
- The hysteresis motor has a low power density and is not suitable for high-power applications.
- The motor is relatively expensive compared to other single-phase motors.
- The motor has a low efficiency at low loads.
The hysteresis motor is a synchronous motor that operates on the principle of hysteresis loss. It is a type of single-phase motor that uses a rotor made of a ferromagnetic material. The motor is designed to produce a rotating magnetic field by using a stator winding that is fed with a single-phase AC supply. The rotor rotates at the same speed as the rotating magnetic field.
Hysteresis Loss
Hysteresis loss is a type of energy loss that occurs in ferromagnetic materials when they are subjected to a varying magnetic field. This loss is due to the resistance of the material to changes in the direction of its magnetization. The loss results in the generation of heat, which can be detrimental to the performance of the motor.
Working of Hysteresis Motor
The hysteresis motor works by exploiting the hysteresis loss in the rotor. The rotor is made of a ferromagnetic material that is highly resistive to changes in the direction of its magnetization. When the stator winding is energized with a single-phase AC supply, a rotating magnetic field is produced. This magnetic field induces a magnetic field in the rotor, causing it to rotate.
The rotor rotates at the same speed as the rotating magnetic field due to the hysteresis loss in the rotor. The hysteresis loss causes the rotor to lag behind the rotating magnetic field, resulting in a torque being produced on the rotor. This torque causes the rotor to rotate at the same speed as the rotating magnetic field.
Advantages of Hysteresis Motor
- The hysteresis motor is highly efficient and has a high power factor.
- It has a simple construction and is easy to maintain.
- The motor operates quietly and is vibration-free.
- The motor has a high starting torque and can be used in applications where high starting torque is required.
Disadvantages of Hysteresis Motor
- The hysteresis motor has a low power density and is not suitable for high-power applications.
- The motor is relatively expensive compared to other single-phase motors.
- The motor has a low efficiency at low loads.
In capacitor start single-phase motors- a)current in the starting winding leads the voltage
- b)current in the starting winding lags the voltage
- c)current in the starting winding is in phase with voltage in running winding
- d)none of the above
Correct answer is option 'A'. Can you explain this answer?
In capacitor start single-phase motors
a)
current in the starting winding leads the voltage
b)
current in the starting winding lags the voltage
c)
current in the starting winding is in phase with voltage in running winding
d)
none of the above
|
|
Divya Singh answered |
Explanation:
Capacitor start single-phase motors are used in applications where high starting torque is required. They are commonly used in air compressors, pumps, and other heavy-duty machinery.
The capacitor start single-phase motor has two windings: the main winding and the starting winding. The main winding is designed to handle the normal running load, while the starting winding is designed to provide the high starting torque required for the motor to start.
The starting winding is connected in series with a capacitor to create a phase shift between the current and voltage in the winding. This phase shift creates a rotating magnetic field that produces the high starting torque.
In capacitor start single-phase motors, the current in the starting winding leads the voltage. This means that the current reaches its peak value before the voltage reaches its peak value.
This phase difference is necessary to create the rotating magnetic field required for the motor to start. Without the phase difference, the motor would not be able to produce the high starting torque required to overcome the inertia of the load.
Conclusion:
In conclusion, the correct answer to the question is that in capacitor start single-phase motors, the current in the starting winding leads the voltage. This phase difference is necessary to create the rotating magnetic field required for the motor to start and produce the high starting torque required to overcome the inertia of the load.
Capacitor start single-phase motors are used in applications where high starting torque is required. They are commonly used in air compressors, pumps, and other heavy-duty machinery.
The capacitor start single-phase motor has two windings: the main winding and the starting winding. The main winding is designed to handle the normal running load, while the starting winding is designed to provide the high starting torque required for the motor to start.
The starting winding is connected in series with a capacitor to create a phase shift between the current and voltage in the winding. This phase shift creates a rotating magnetic field that produces the high starting torque.
In capacitor start single-phase motors, the current in the starting winding leads the voltage. This means that the current reaches its peak value before the voltage reaches its peak value.
This phase difference is necessary to create the rotating magnetic field required for the motor to start. Without the phase difference, the motor would not be able to produce the high starting torque required to overcome the inertia of the load.
Conclusion:
In conclusion, the correct answer to the question is that in capacitor start single-phase motors, the current in the starting winding leads the voltage. This phase difference is necessary to create the rotating magnetic field required for the motor to start and produce the high starting torque required to overcome the inertia of the load.
In a split phase motor, the running winding should have- a)high resistance and low inductance
- b)low resistance and high inductance
- c)high resistance as well as high inductance
- d)low resistance as well as low inductiance
Correct answer is option 'B'. Can you explain this answer?
In a split phase motor, the running winding should have
a)
high resistance and low inductance
b)
low resistance and high inductance
c)
high resistance as well as high inductance
d)
low resistance as well as low inductiance
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Upasana Joshi answered |
Understanding Split Phase Motors
Split phase motors are widely used in various applications due to their simplicity and efficiency. They consist of two windings: the starting winding and the running winding. The properties of these windings play a crucial role in the motor's performance.
Characteristics of Running Winding
The running winding is designed to ensure smooth operation and effective performance. Here’s why it should have low resistance and high inductance:
Low Resistance
- Efficiency: Low resistance in the running winding minimizes power losses due to heat generated during operation. This increases the overall efficiency of the motor.
- Higher Current Flow: With low resistance, the motor can draw more current, which is essential for maintaining torque during operation.
High Inductance
- Synchronous Operation: High inductance helps create a phase shift between the current and voltage, essential for developing a rotating magnetic field, which is necessary for motor operation.
- Smooth Operation: Inductance provides reactance that helps in stabilizing the motor's operation, leading to smoother running and less vibration.
Conclusion
In summary, the running winding of a split phase motor should possess low resistance and high inductance to ensure efficient energy usage and effective motor performance. This combination allows the motor to operate reliably under varying load conditions, making it suitable for a wide range of applications.
Split phase motors are widely used in various applications due to their simplicity and efficiency. They consist of two windings: the starting winding and the running winding. The properties of these windings play a crucial role in the motor's performance.
Characteristics of Running Winding
The running winding is designed to ensure smooth operation and effective performance. Here’s why it should have low resistance and high inductance:
Low Resistance
- Efficiency: Low resistance in the running winding minimizes power losses due to heat generated during operation. This increases the overall efficiency of the motor.
- Higher Current Flow: With low resistance, the motor can draw more current, which is essential for maintaining torque during operation.
High Inductance
- Synchronous Operation: High inductance helps create a phase shift between the current and voltage, essential for developing a rotating magnetic field, which is necessary for motor operation.
- Smooth Operation: Inductance provides reactance that helps in stabilizing the motor's operation, leading to smoother running and less vibration.
Conclusion
In summary, the running winding of a split phase motor should possess low resistance and high inductance to ensure efficient energy usage and effective motor performance. This combination allows the motor to operate reliably under varying load conditions, making it suitable for a wide range of applications.
Chapter doubts & questions for Single-Phase Induction Motors - Electrical Machines for Electrical Engg. 2025 is part of Electrical Engineering (EE) exam preparation. The chapters have been prepared according to the Electrical Engineering (EE) exam syllabus. The Chapter doubts & questions, notes, tests & MCQs are made for Electrical Engineering (EE) 2025 Exam. Find important definitions, questions, notes, meanings, examples, exercises, MCQs and online tests here.
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