In brushless excitation system of modern alternators, the main exciter is dc gen

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Question
In brushless excitation system of modern alternators, the main exciter is
Options
A. dc generator
B. ac generator
C. either dc or ac generator
D. induction generator

Correct Answer

ac generator

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4. Assertion (A): A transistor has lower voltage drop during conduction as compared to thyristor
Reason (R): Transistors are manufactured in very high voltage and current ratings.
Options
A. Both A and R are correct and R is correct explanation of A
B. Both A and R correct but R is not correct explanation of A
C. A is correct but R is wrong
D. A is wrong but R is correct

8. A separately excited dc motor is run from a dc source through a chopper. At 600 rpm and rated torque, the duty cycle of chopper is 0.8. At 600 rpm and half the rated torque, the duty cycle is likely to be
Options
A. 0.9
B. 0.8
C. 0.75
D. 0.6

9. In a 3 phase full converter, the firing angle is less than 60�. The instantaneous output voltage
Options
A. will have positive part only
B. will have both positive and negative parts
C. may have both positive and negative parts
D. will have negative part if load is inductive

10. As compared to BJT, MOSFET has
Options
A. lower switching losses and higher conduction losses
B. higher switching losses and higher conduction losses
C. higher switching losses and lower conduction losses
D. lower switching losses and lower conduction losses

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