In a 3 phase full converter, the firing angle is less than 60�. The instantaneou

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Question
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

Correct Answer

will have positive part only

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1. 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

6. 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

7. In pulse width modulation of chopper
Options
A. T is kept constant and T_on is varied
B. T_on is kept constant T is varied
C. both T and T_on are varied
D. either T or T_on is varied

8. All other parameters remaining the same, a 3 phase bridge inverter with 180� mode of operation
Options
A. has the same peak thyristor current as in 120� mode of operation
B. has higher peak thyristor current than in 120� mode of operation
C. has lower peak thyristor current than in 120� mode of operation
D. any of the above

9. A class D chopper
Options
A. can operate in first quadrant only
B. can operate in second quadrant only
C. can operate in either first or fourth quadrant
D. can operate in all the quadrants

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