Filed Under: Synchronous Motor MCQs
Contents
- 1 Speed regulation of synchronous motor is
- 2 An over-excited synchronous motor
- 3 If one of 3-phases is short-circuited, the induction motor will
- 4 Hunting in synchronous motor happens due to
- 5 The operating speed of the synchronous motor can be changed by
- 6 The load on synchronous motor running with fixed excitation in doubled, the torque angle becomes
- 7 Stability and excitation of synchronous motors are
- 8 For same parameters the PF of the synchronous motor is
- 9 Maximum power is developed at a load angle of
Speed regulation of synchronous motor is
Speed regulation of synchronous motor is:
- 0
- 5
- 89
- 100
Correct answer: 1. 0
Explanation: Speed regulation of machine is defined as the ratio:
SR = {S (NL) – S (FL)} / S(FL)
where S (NL) = Speed of motor at no load
S (FL) = Speed of motor at full load.
The speed synchronous motor remains constant from no load to full load thus the
An over-excited synchronous motor
An over-excited synchronous motor:
- Takes reactive power
- Supplies reactive power
- Neither takes nor supplies
- Any of above
Correct answer: 2. Supplies reactive power
Explanation: Such motor draws current at leading PF and behaves as large capacitor. It can be used for power factor correction equipment.
Synchronous motors are started by
Synchronous motors are started by:
- Using external prime mover
- Using Amortisseur windings
- Reducing speed of stators magnetic field
- All of above
Correct answer: 4. All of above
If one of 3-phases is short-circuited, the induction motor will
If one of 3-phases is short-circuited, the induction motor will:
- Not start
- Overheat
- Continue to work as it did previously
- None of above
Correct answer: 2. Overheat
Hunting in synchronous motor happens due to
Hunting in synchronous motor happens due to:
- Change in load
- Change in excitation
- Change in frequency of the supply
- Any of above
- None of above
Correct answer: 4. Any of above
The operating speed of the synchronous motor can be changed by
The operating speed of the synchronous motor can be changed by:
- Changing supply frequency
- Changing connected load
- Changing voltage
- Changing excitation method
Correct answer: 1. Changing supply frequency
The load on synchronous motor running with fixed excitation in doubled, the torque angle becomes
The load on synchronous motor running with fixed excitation in doubled, the torque angle becomes:
- Halved
- Remains constant
- Doubled
- 7.99 of original
Correct answer: 3. Doubled
Stability and excitation of synchronous motors are
Stability and excitation of synchronous motors are:
- Directly related
- Inversely related
- Exponentially related
- Not related
Correct answer: 1. Directly related
For same parameters the PF of the synchronous motor is
For same parameters the PF of the synchronous motor is:
- Better than induction
- Worst than induction
- Identical to induction
- Any of above
Correct answer: 1. Better than an induction motor
Explanation: The stator supply of synchronous motor is relieved from producing a magnetic field
Maximum power is developed at a load angle of
Maximum power is developed at a load angle of:
- 45º
- 60º
- 75º
- 90º
Correct answer: 4. 90º
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