Q31 · Electrical Machines · MSQ · 1 mark
A 220V/12V single-phase transformer is designed for use in India and rated 100 VA at 50 Hz. Later, this unit is shipped to the USA where it is used as a 110V/6V transformer at 60 Hz.
Which of the following statements is/are correct?
- (A)No-load current drawn would be smaller for operation in the USA compared to that in India
- (B)For the same load current, the losses would be higher in the USA compared to that in India
- (C)The peak magnetic flux density in the core would be higher while operating in the USA compared to that in India
- (D)The eddy current losses in the core would be approximately 44% higher while operating in the USA compared to that in India
Answer (official key): A
Solution
The core flux is set by : India , USA . So the peak flux density in the USA is about 42% of the Indian value.
- (A) True: lower flux gives a smaller magnetizing (no-load) current.
- (B) False: core losses fall and copper loss is unchanged, so losses are lower, not higher.
- (C) False: the peak flux density is lower.
- (D) False.



