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Electrical Machines Practice Test: DC Machines
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Avg score: 100% Most missed: “Swineburne’s test is applicable to those machines in which flux is practically _…”
DC Machines topics are: DC machine applications and its circuit models, mmf and flux density waveforms in DC machines, methods of excitation, efficiency and testing of dc machines. DC machines, which can be classified as DC motors and DC generators, convert mechanical energy into electrical energy. They contain AC currents and voltages, but convert AC voltage to DC voltage. DC machines are used in applications where high starting torque and accurate speed control over a wide range are important.  Here are some types of DC machines: DC motors: Use direct current to produce mechanical force.... Show more
Electrical Machines Practice Test: DC Machines
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25 Questions

1. The efficiency in the swineburne’s test can be found.
2. Consider a 200V, 25kW, 30A DC machine lap connected with armature resistance of 0.4 ohms. If the machine is later wave wound, then the developed power is?
3. Which is the most appropriate relation to find efficiency of the generator?
4. A 400-V, 1000-A, lap wound dc machine has 10 poles, 860 armature conductors. The number of conductors in the pole face to give full compensation if pole face covers 70% of pole span is?
5. Centrifugal pumps, fans-blowers use __________
6. If a dc shunt motor is stopped by forcing starter handle back to OFF position, then the __________
7. In the hopkinson’s test on two DC machines. Machine A has field current of 1.4A and B has field current of 1.3A. Which machine acts as motor?
8. Compensating winding has an advantage of __________
9. What is the shaft power at the DC Generator?
10. If the electromagnetic torque in a DC shunt-generator is opposite, what can be further concluded?
11. ______ test is used for determining the efficiency of a traction motor.
12. The brushes are placed __________
13. Most commercial compound dc generator are normally supplied by manufacturers as over compound machines because __________
14. Swineburne’s test is applicable to those machines in which flux is practically _______
15. The self-excited dc generator with gradual build up of residual voltage and EMF corresponds to __________
16. Interpoles are used to start the dc motor above the base speed.
17. Which method needed to limit cross-magnetizing effect?
18. Mark the most incorrect. In dc generator, commutation can be improved by __________
19. The commutation process involves basically reversal of current in armature coil as it crosses MNA.
20. Hopkinson’s test is also called regenerative test due to ____________
21. If the field current and armature current are reversed, then the __________
22. The principle contributors to magneto motive force is/are __________
23. A dc shunt motor is connected to the source through 3-point starter. If the field id kept open and starter handle is moved from off to on position, then __________
24. A dc shunt motor is running at 1000 rpm at the rated load torque. If few of the field windings get shot circuited then the __________
25. In the Hopkinson’s test on two DC machines. Machine A has field current of 1.4A and B has field current of 1.3A. Which machine acts as generator?