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The rotor of an induction motor cannot run at synchronous speed because:
- a)Stator flux would then become zero
- b)Losses would increase
- c)Rotor torque would then become zero
- d)Induction rotor would then become synchronous motor
Correct answer is option 'C'. Can you explain this answer?
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Verified Answer
The rotor of an induction motor cannot run at synchronous speed becaus...
Synchronous speed is the speed of rotation of the magnetic field in a rotary machine. An induction motor always runs at a speed less than synchronous speed.
The rotating magnetic field which is produced in the stator will generate flux in the rotor which will make the rotor to rotate. But due to the lagging of rotor flux current with respect to stator flux current, the rotor will never reach to its rotating magnetic field speed i.e. the synchronous speed.
If the motor is running at synchronous speed, then the torque generated by the motor equal to zero. If rotor runs at synchronous speed as the field of the stator, this will cause the slip to become zero, then there will be no torque generated in rotor.
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The rotor of an induction motor cannot run at synchronous speed becaus...
Explanation:
The rotor of an induction motor cannot run at synchronous speed because the rotor torque would then become zero.
Induction Motor Operation:
An induction motor works on the principle of electromagnetic induction. It consists of a stator (stationary part) and a rotor (rotating part). The stator is fed with a three-phase alternating current, which creates a rotating magnetic field. This rotating magnetic field induces currents in the rotor, which in turn creates a magnetic field. The interaction between the stator and rotor magnetic fields produces a torque that causes the rotor to rotate.
Synchronous Speed:
The synchronous speed of an induction motor is the speed at which the rotating magnetic field of the stator rotates. It is given by the formula:
Synchronous Speed = (120 * Frequency) / Number of Poles
Why the Rotor Cannot Run at Synchronous Speed:
If the rotor of an induction motor runs at synchronous speed, the rotor speed will be equal to the speed of the rotating magnetic field of the stator. In this case, the relative speed between the stator and rotor magnetic fields will be zero.
Effect on Rotor Torque:
The torque produced in an induction motor is directly proportional to the relative speed between the stator and rotor magnetic fields. When the rotor runs at synchronous speed, the relative speed becomes zero, resulting in zero torque production. Therefore, the rotor torque would then become zero.
Consequences:
If the rotor torque becomes zero, the motor will not be able to develop any torque to drive the load. The motor will stall and will not be able to start or operate. It will behave like a synchronous motor, which requires external means (such as a prime mover or a static frequency converter) to bring it to synchronous speed.
Therefore, in order for an induction motor to operate properly, the rotor speed must always be less than the synchronous speed. This difference in speed, known as slip, allows the motor to develop torque and drive the load.
The rotor of an induction motor cannot run at synchronous speed because the rotor torque would then become zero.
Induction Motor Operation:
An induction motor works on the principle of electromagnetic induction. It consists of a stator (stationary part) and a rotor (rotating part). The stator is fed with a three-phase alternating current, which creates a rotating magnetic field. This rotating magnetic field induces currents in the rotor, which in turn creates a magnetic field. The interaction between the stator and rotor magnetic fields produces a torque that causes the rotor to rotate.
Synchronous Speed:
The synchronous speed of an induction motor is the speed at which the rotating magnetic field of the stator rotates. It is given by the formula:
Synchronous Speed = (120 * Frequency) / Number of Poles
Why the Rotor Cannot Run at Synchronous Speed:
If the rotor of an induction motor runs at synchronous speed, the rotor speed will be equal to the speed of the rotating magnetic field of the stator. In this case, the relative speed between the stator and rotor magnetic fields will be zero.
Effect on Rotor Torque:
The torque produced in an induction motor is directly proportional to the relative speed between the stator and rotor magnetic fields. When the rotor runs at synchronous speed, the relative speed becomes zero, resulting in zero torque production. Therefore, the rotor torque would then become zero.
Consequences:
If the rotor torque becomes zero, the motor will not be able to develop any torque to drive the load. The motor will stall and will not be able to start or operate. It will behave like a synchronous motor, which requires external means (such as a prime mover or a static frequency converter) to bring it to synchronous speed.
Therefore, in order for an induction motor to operate properly, the rotor speed must always be less than the synchronous speed. This difference in speed, known as slip, allows the motor to develop torque and drive the load.
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The rotor of an induction motor cannot run at synchronous speed because:a)Stator flux would then become zerob)Losses would increasec)Rotor torque would then become zerod)Induction rotor would then become synchronous motorCorrect answer is option 'C'. Can you explain this answer?
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