Hysteresis Motor MCQ :: Single Phase Motor

1. A hysteresis motor is a ______ with a uniform air gap and without DC excitation.

1. DC Motor
2. Synchronous motor
3. Induction Motor
4. AC motor

Explanation:- A hysteresis motor is a synchronous motor with a uniform air gap and without DC excitation.

2. The torque in a hysteresis motor is produced due to the ______  induced in the rotor.

1. Stator Current
2. Non-magnetic field
3. Hysteresis current
4. Hysteresis flux

Explanation:- The torque in a hysteresis motor is produced due to the hysteresis current induced in the rotor by the action of the rotating flux of the stator windings.  A hysteresis motor works on the principle of hysteresis losses. Hysteresis loss is caused by the magnetization and demagnetization of the core as current flows in the forward and reverse directions.

3. The type of rotor used in Hysteresis motor is

1. Cylindrical pole type
2. Salient pole
3. Both 1 & 2
4. None of the above

Explanation: A hysteresis motor is a single-phase cylindrical (non-salient pole type) synchronous induction motor. Non-Salient rotors have smaller diameters and longer axial lengths. They are used for High-speed operation (typically speed will be 1500 and 3000 rpm).

4. The area of a hysteresis loop for the magnetic material used in the rotor of a hysteresis motor should be:

1. Medium
2. Very large
3. Infinite
4. Very small

Explanation:-  In hysteresis Motor the hysteresis losses are very high. As the hysteresis losses are directly proportional to the area of the hysteresis loop, the hysteresis loop is very large.

5. The noise level of the hysteresis motor is very______

1. High
2. Medium
3. Low
4. No Noise

Explanation:- The noise level of the hysteresis motor is very low as compared to the induction motor because it operates at a constant speed and its rotor is smooth.

6. The starting torque of Hysteresis Motor is

1. High
2. Low
3. Moderate
4. Zero

Explanation:-  Hysteresis Motor has high starting torque as it has high rotor hysteresis loss. A high starting torque is produced as a result of the high rotor resistance (proportional to the hysteresis loss).

7.  The rotor of the hysteresis motor is made up ______

1. Permanent Magnet
2. Non-Permanent magnet
3. Either 1 or 2
4. None of the above

Explanation:- The rotor of the hysteresis motor is made up of ceramic permanent magnetic material, therefore, it is difficult to set up an eddy current in such a rotor due to the high resistivity of magnetic materials like ceramic.

8. The different types of losses in a Hysteresis Motor are

1. Eddy current Losses
2. Harmonic Losses
3. Hysteresis Losses
4. Both Eddy current & Hysteresis Losses

Explanation:- The rotor of the hysteresis motor is made up of ceramic permanent magnetic material, therefore, it is difficult to set up an eddy current in such a rotor due to the high resistivity of magnetic materials like ceramic. Hence there is no eddy current loss but only hysteresis loss.

9. The rotor of a hysteresis motor is made of ceramic permanent magnet material, which causes:

1. Stationary flux
2. No hysteresis losses
3. High eddy current losses
4. No eddy current losses

Explanation:- The rotor of the hysteresis motor is made up of ceramic permanent magnetic material, therefore, it is difficult to set up an eddy current in such a rotor due to the high resistivity of magnetic materials like ceramic. Hence there is no eddy current loss but only hysteresis loss.

10. Hysteresis motor is employed for high-quality tape recorders. The most probable reason for the same is:

1. Constant (Synchronous) speed
2. Unaffected by mechanical vibrations
4. Centrifugal switch is not required

Explanation:– The torque of the Hysteresis motor is uniform (steady) from standstill to synchronous speed. Since the rotor has no teeth or salient poles or winding, a hysteresis motor is inherently quiet and produces smooth rotation of the load.

11. In Hysteresis Motor ______ is designed to produce a synchronously-revolving field from a single-phase supply.

1. Stator
2. Rotor
3. Either 1 or 2
4. None of the above

Explanation:- In Hysteresis Motor stator is designed to produce a synchronously-revolving field from a single-phase supply. This is accomplished by using permanent-split capacitor type construction. Consequently, both the windings (i.e., starting as well as main winding) remain connected in the circuit during running operation as well as at starting.

12. In a single-phase hysteresis motor, the rotor cylinder is made up of ______.

1. Magnetically hard cobalt steel
2. Magnetically smooth chrome steel
3. Steel laminations
4. Solid steel

Explanation:- The rotor of the hysteresis motor is made up of a magnetically smooth chrome steel cylinder and it has no winding. The rotor ring of the hysteresis motor made up of special magnetic material such as magnetically hard chrome or cobalt steel having a wide hysteresis loop.

13. In a single-phase hysteresis motor, the retentivity of the rotor is

1. Low
2. Moderate
3. Zero
4. High

Explanation:- Retentivity is the ability of a material to retain a magnetic field. In a single-phase hysteresis motor the rotor of the motor is made up of a magnetically smooth chrome steel cylinder. Hence the retentivity of the rotor is high.

14. The rotor of the hysteresis motor moves synchronously due to ____

1. High Retentivity
2. Magnetic Locking
3. Magnetic Surfacing
4. Magnetic Hysteresis Ring

Explanation:- The rotor of the hysteresis motor moves synchronously because the pole of the motor magnetically locks with the stator which has opposite polarities.

15. The area of a hysteresis loop for the magnetic material used in the rotor of a hysteresis motor should be:

1. Medium
2. Very large
3. Infinite
4. Very small

Explanation: A hysteresis motor is a synchronous motor with a uniform air gap and without DC excitation. In hysteresis motor, the hysteresis losses are very high. As the hysteresis losses are directly proportional to the area of the hysteresis loop, the hysteresis loop is very large.

16. The rotor of a hysteresis motor is made of ceramic permanent magnet material, which causes:

1. No hysteresis losses
2. Stationary flux
3. No eddy current losses
4. High eddy current losses

Explanation:
The rotor of the hysteresis motor is made up of ceramic permanent magnetic material, therefore, it is difficult to set up an eddy current in such a rotor due to the high resistivity of magnetic materials like ceramic. Hence there is no eddy current loss but only hysteresis loss.

17. Which of the following motors has no winding on its rotor?

1. Single phase Induction
2. DC shunt
3. Hysteresis
4. Universal

Explanation: Hysteresis motor is a single-phase synchronous motor with a cylindrical rotor made up of ferromagnetic material and does not require any DC excitation to the rotor. The rotor is the smooth cylindrical type made up of hard magnetic material like chrome steel or alnico for high retentivity. The rotor does not carry any winding or teeth.

18. A rotating electrical machine having its self-inductance of both stator and rotor winding independent of its rotor position will definitely not develop

1. Starting torque
2. Synchronizing torque
3. Hysteresis torque
4. Reluctance torque

Explanation:
If the induction is constant irrespective of rotor position that means reluctance is constant.  The self-inductance of the winding is independent of the position of the rotor due to the round and symmetric shape of the rotor. The stator, i.e., the armature has a cylindrical structure. Hence, the self-inductance of the rotor field winding will not depend upon the position of the rotor and will be a constant one.

In cylindrical machines, the rotor as well as stator is round with a uniform air gap. If the effects of slots on the stator and rotor are neglected, the reluctance of the magnetic path is independent of the position of the rotor Therefore, self-inductance constant and no reluctance torque will be produced.

As the rotor is cylindrical, the reluctance by the stator-produced flux will be the same irrespective of the rotor position. Hence No reluctance torque can be produced.

19. Which of the following motor is most steady in operation?

1. Reluctance Motor
2. Hysteresis Motor
3. Reactance Motor
4. Synchronous Motor