1. An transformer will have maximum efficiency at a load such that
Answer: Copper loss = iron loss
2. What is the primary disadvantage of reluctance motors?
Answer: Low starting torque
3. What is the current transformer?
Answer: Used to measure AC current
4. What is the primary function of a DC motor?
Answer: To convert electrical energy into mechanical energy
5. What is the primary function of a stepper motor?
Answer: To rotate in precise steps or increments
6. The capacity of a 3-phase transformer is typically rated in:
Answer: Kilovolt-amperes (kVA)
7. Which of the following is a disadvantage of 3-phase transformers compared to single-phase transformers?
Answer: Higher cost
8. Welding transformers work on principle that weld is actually
Answer: Short circuit
9. Which of the following is NOT a common fault in a 3-phase transformer?
Answer: Excessive magnetic flux
10. What is the voltage relationship between the primary and secondary windings in a 3-phase transformer with a Delta-Star configuration?
Answer: The primary voltage is √3 times the secondary voltage
11. A transformer transforms
Answer: Voltage and current
12. Which of the following is the most common driver used for controlling a stepper motor?
Answer: Stepper motor controller
13. What is the effect of increasing the armature resistance in a DC motor?
Answer: The torque of the motor decreases
14. An ideal transformer
Answer: All of these (no losses, 100% efficiency, etc.)
15. Which of the following stepper motor driving modes gives the best torque performance?
Answer: Full-step mode
16. What is the function of a breather in a transformer?
Answer: To arrest flow of moisture when outside air enters the transformer
17. Current transformers are
Answer: Series connected type of instrument transformers
18. What is the purpose of the brushes in a DC generator?
Answer: To maintain contact with the commutator
19. Which of the following is a feature of a compound-wound DC motor?
Answer: The field windings are connected in both series and parallel
20. In a three-phase transformer, what will happen if one phase is lost?
Answer: The transformer will continue functioning, but it may be overloaded or unbalanced. It doesn't stop functioning completely.
21. Which of the following is a characteristic of a reluctance motor?
Answer: It has a rotating magnetic field
22. Which of the following is a characteristic of a series generator?
Answer: The field winding is connected in series with the armature
23. Which type of DC motor is most commonly used in electric fans?
Answer: Universal motor
24. The efficiency of an ideal transformer is:
Answer: 1 (100%)
25. The primary and secondary induced emf E1 and E2 in two winding transformer are always
Answer: Proportional to the turns ratio. They are not always equal in magnitude.
26. In a DC motor, the torque is proportional to the:
Answer: Armature current
27. The ratio of the number of turns in the primary coil to the number of turns in the secondary coil is called the:
Answer: Turns ratio
28. What is the function of a transformer?
Answer: Transformer is used to step down or up the AC voltages and currents
29. The main purpose of using core in a transformer is to
Answer: Decrease reluctance of the common magnetic circuit
30. What is the typical application of a stepper motor?
Answer: Precision positioning systems
31. In a reluctance motor, the rotor is made of:
Answer: Soft iron
32. Voltage regulation of transformer is given by
Answer: (V2 - E2) / E2
33. Which of the following transformer configurations is commonly used for high-voltage transmission?
Answer: Star-Delta
34. A transformer with 1000 primary turns is connected to a 250 V AC supply. For secondary voltage of 400 V, the number of secondary turns should be
Answer: 1600
35. A step-up transformer increases
Answer: Voltage
36. E21:F23+#REF!
Answer: This seems like an error or formula reference. It doesn't make sense as an answer.
37. =E21:F23+#REF!
Answer: This also seems like a formula reference error. Please check the formula.
38. In a stepper motor, what determines the number of steps in one full rotation?
Answer: The winding configuration
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