200 Important Synchronous Motor MCQ Question and Answer | PDF Free Download
1.During short circuit test on a synchronous motor ____ are short circuited
- Aarmature terminals
- Bfield terminals
- Call stator phase windings
- Done of the stator phase winding
2.The rotor copper losses of a synchronous motor are met by
- AArmature input
- BDc source
- CAc supply mains
- DNone of these
3.The efficiency of a properly designed synchronous machine will usually fall in range
- A60 to 70%
- B75 to 80%
- C85 to 95%
- D99 to 99.5%
4.The negative phase sequence in a 3-phase synchronous motor exists when the motor is
- AUnder loaded
- BOverloaded
- CSupplied with unbalanced voltage
- DHot
5.In case one phase of a 3-phase synchronous motor is short circuited, the motor will
- ANot start
- BRun at 2/3 of synchronous speed
- CRun with excessive vibrations
- DTake less than the rated load
6.A synchronous motor may fail to pull into synchronous owing to
- AExcessive load
- BLow excitation
- CHigh friction
- DAny of these
7.Which of the following is not the advantage of a synchronous motor?
- AOperating over a wide range of power factor from lagging to leading
- BIt can always be adjusted to operate at unity power for optimum efficiency and economy
- CIts rotor has 2 slip rings
- DOperation at constant speed from no load to pull load
8.Which of the following synchronous motor has cost comparable to that of an induction motor?
- AHigh kW output high speed
- BHigh kW output low speed
- CLow kW output low speed
- DLow kW output high speed
9.A 3-phase synchronous motor is widely used for
- APower factor improvement
- BControl of voltage at the end of a transmission line
- CFluctuating loads
- DBoth (a) and (b)
10.Synchronous motors are not used
- AIn power houses and substations in parallel to bus bars for pf correction
- BIn factories having large number of induction motors and other power apparatus operating at lagging power factor for pf improvement
- CFor driving electric trains cranes, machine tools and line shaft drives
- DFor driving continuously operating and constant speed equipment such as centrifugal pumps, fans blowers, ammonia and air compressors motor generator sets etc.
11.3 phase synchronous motor needs
- A3 phase AC supply only
- B3 phase AC supply as well as single phase AC supply
- C3 phase AC supply as well as DC supply
- DDC supply only