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Test: Single-Phase Induction Motors - 1 - Electrical Engineering (EE) MCQ


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10 Questions MCQ Test GATE Electrical Engineering (EE) Mock Test Series 2025 - Test: Single-Phase Induction Motors - 1

Test: Single-Phase Induction Motors - 1 for Electrical Engineering (EE) 2024 is part of GATE Electrical Engineering (EE) Mock Test Series 2025 preparation. The Test: Single-Phase Induction Motors - 1 questions and answers have been prepared according to the Electrical Engineering (EE) exam syllabus.The Test: Single-Phase Induction Motors - 1 MCQs are made for Electrical Engineering (EE) 2024 Exam. Find important definitions, questions, notes, meanings, examples, exercises, MCQs and online tests for Test: Single-Phase Induction Motors - 1 below.
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Test: Single-Phase Induction Motors - 1 - Question 1

In a split phase motor

Detailed Solution for Test: Single-Phase Induction Motors - 1 - Question 1
Explanation:

  • Split-phase motor: A split-phase motor is a type of single-phase induction motor that has two windings known as the main winding and the auxiliary winding.

  • Starting winding: The starting winding is used to provide the initial torque necessary to start the motor.

  • Centrifugal switch: In a split-phase motor, the starting winding is connected through a centrifugal switch. The centrifugal switch is a device that is activated by the motor's rotation speed. When the motor reaches a certain speed, the centrifugal switch disconnects the starting winding from the circuit to prevent overheating and damage to the motor.

  • Function of centrifugal switch: The centrifugal switch ensures that the starting winding is only active during the startup phase of the motor and is disconnected once the motor reaches its operating speed.

  • Running winding: The running winding is the winding responsible for providing the continuous torque needed to keep the motor running once it has started.

  • Conclusion: In a split-phase motor, the starting winding is connected through a centrifugal switch to control its operation and prevent overheating, making option A the correct answer.

Test: Single-Phase Induction Motors - 1 - Question 2

In a ceilingfan employing capacitor run motor

Detailed Solution for Test: Single-Phase Induction Motors - 1 - Question 2
Explanation:

  • Ceiling Fan Motor: A ceiling fan motor typically employs a capacitor run motor for efficient operation.

  • Primary and Secondary Windings: In a capacitor run motor, the secondary winding surrounds the primary winding.

  • Function: The primary winding is responsible for creating a magnetic field when an alternating current passes through it. The secondary winding then interacts with this magnetic field to generate the torque required to drive the fan blades.

  • Efficiency: This arrangement of windings ensures efficient operation of the ceiling fan motor, providing the necessary power to circulate air effectively.

  • Common Arrangement: The primary winding being surrounded by the secondary winding is a usual arrangement in capacitor run motors used in ceiling fans.

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Test: Single-Phase Induction Motors - 1 - Question 3

Which type of load is offered by cranes and hoists ?

Detailed Solution for Test: Single-Phase Induction Motors - 1 - Question 3
Types of loads offered by cranes and hoists:

  • Gradually varying load: Cranes and hoists often deal with loads that gradually increase or decrease in weight over time. This type of load requires careful control and precision in lifting and moving.

  • Non-reversing, no-load start: Some cranes and hoists may encounter situations where they need to start moving a load without any reversing motion and without any initial load. This type of start requires a different set of controls and mechanisms.

  • Reversing, light start: In some cases, cranes and hoists may need to lift a light load that requires reversing motion at the start. This type of load also requires precise control to ensure the safety of the operation.

  • Reversing, heavy start: Cranes and hoists may also encounter situations where they need to lift a heavy load with reversing motion at the start. This type of load is challenging and requires strong and reliable equipment to handle the weight.


In conclusion, cranes and hoists offer a variety of loads, each requiring specific control and handling techniques to ensure safe and efficient operation.

Test: Single-Phase Induction Motors - 1 - Question 4

Which of the following motors is preferred for tape-recorders?

Detailed Solution for Test: Single-Phase Induction Motors - 1 - Question 4
Preferred Motor for Tape Recorders: Hysteresis Motor

  • Low Noise: Hysteresis motors are known for their quiet operation, making them ideal for tape recorders where noise can affect the recording quality.


  • Smooth Operation: Hysteresis motors provide smooth and consistent rotation, which is crucial for maintaining a steady tape speed in tape recorders.


  • Low Maintenance: These motors have a simple design with few moving parts, resulting in low maintenance requirements, which is beneficial for long-term use in tape recorders.


  • High Torque: Hysteresis motors offer high starting torque, allowing them to quickly reach the desired rotational speed for tape recorder applications.


  • Stable Speed: These motors have excellent speed stability, ensuring accurate recording and playback speeds in tape recorders.


Therefore, the hysteresis motor is the preferred choice for tape recorders due to its quiet operation, smooth performance, low maintenance requirements, high torque, and speed stability.
Test: Single-Phase Induction Motors - 1 - Question 5

Which of the following motors is used in mixies ?

Detailed Solution for Test: Single-Phase Induction Motors - 1 - Question 5
Explanation:

  • Universal motor: Mixies typically use universal motors due to their high speed and ability to generate high torque at low speeds, making them ideal for blending and grinding tasks.

  • Characteristics of universal motors:

    • Can operate on both AC and DC power sources.

    • High speed and high torque capabilities.

    • Compact and lightweight design.

    • Cost-effective compared to other motor types.



  • Working principle:

    • Universal motors operate on the principle of electromagnetism, where an electric current passing through a coil in a magnetic field generates rotational motion.

    • They have a commutator and brushes to ensure the continuous flow of current, allowing them to run efficiently at varying speeds.



  • Applications:

    • Aside from mixies, universal motors are used in power tools, vacuum cleaners, and kitchen appliances due to their versatility and performance capabilities.



Test: Single-Phase Induction Motors - 1 - Question 6

A hysteresis motor works on the principle of

Detailed Solution for Test: Single-Phase Induction Motors - 1 - Question 6
Principle of a Hysteresis Motor

  • Hysteresis Loss: A hysteresis motor operates based on hysteresis loss, which is the energy lost when a magnetic material is magnetized in one direction and then demagnetized.

  • Rotating Magnetic Field: The stator of the motor generates a rotating magnetic field, which induces eddy currents in the rotor.

  • Permanent Magnet Rotor: The rotor of a hysteresis motor is made of a material with high hysteresis loss characteristics, such as a permanent magnet material.

  • Delayed Alignment: The hysteresis loss in the rotor material causes a delay in alignment with the rotating magnetic field, resulting in the rotor rotating in the same direction as the magnetic field.

  • Low Slip: Hysteresis motors have low slip, meaning the rotor speed closely follows the speed of the rotating magnetic field.

Test: Single-Phase Induction Motors - 1 - Question 7

The value of starting capacitor of a fractional horse power motor will be

Detailed Solution for Test: Single-Phase Induction Motors - 1 - Question 7
Calculation of Starting Capacitor Value for Fractional Horsepower Motor

  • Step 1: Determine the horsepower (HP) rating of the motor.

  • Step 2: Calculate the power factor of the motor.

  • Step 3: Use the formula: Starting Capacitor (in uF) = 1350 x HP / (Voltage x Power Factor)


Explanation

  • Horsepower (HP) Rating: Fractional horsepower motors typically have a rating of less than 1 HP.

  • Power Factor: The power factor of a motor is typically between 0.8 and 0.9.

  • Formula: The formula for calculating the starting capacitor value takes into account the horsepower, voltage, and power factor of the motor.

  • Value: For a fractional horsepower motor, the starting capacitor value is typically around 300 uF.


By following the steps and calculations outlined above, you can determine the appropriate starting capacitor value for a fractional horsepower motor.
Test: Single-Phase Induction Motors - 1 - Question 8

In a two value capacitor motor, the capacitor used for running purposes is

Detailed Solution for Test: Single-Phase Induction Motors - 1 - Question 8
Explanation:

  • Two value capacitor motor: In a two value capacitor motor, two capacitors are used - one for starting purposes and the other for running purposes.

  • Capacitor for running purposes: The capacitor used for running purposes in a two value capacitor motor is typically a paper spaced oil filled type capacitor.

  • Paper spaced oil filled type capacitor: This type of capacitor is designed to handle the continuous operation and voltage requirements of the motor during its running cycle.

  • Advantages of paper spaced oil filled type capacitor:

    • High reliability and durability

    • Good performance in continuous running conditions

    • Ability to handle the heat generated during motor operation



Test: Single-Phase Induction Motors - 1 - Question 9

In capacitor start single-phase motors

Detailed Solution for Test: Single-Phase Induction Motors - 1 - Question 9
Explanation:

  • Current in the starting winding leads the voltage: In capacitor start single-phase motors, the starting winding is connected in series with a capacitor. This creates a phase shift between the current and voltage in the starting winding. The current in the starting winding leads the voltage, creating a rotating magnetic field that helps in starting the motor.

Test: Single-Phase Induction Motors - 1 - Question 10

In a hysteresis motor, the rotor must have

Detailed Solution for Test: Single-Phase Induction Motors - 1 - Question 10
Explanation:

  • Role of the Rotor: The rotor in a hysteresis motor plays a crucial role in the operation of the motor.

  • Requirement of Retentivity: The rotor must have retentivity, which is the ability to retain magnetization even after the magnetizing force is removed.

  • Importance of Retentivity: Retentivity in the rotor ensures that the motor maintains a constant magnetic field, which is essential for its operation.

  • Effect on Motor Performance: Without retentivity in the rotor, the motor would not be able to generate the necessary torque to function effectively.

  • Conclusion: Therefore, it is essential for the rotor in a hysteresis motor to have retentivity to ensure smooth and efficient operation of the motor.

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