Exercise: Power Electronics

Questions for: Power Electronics

If duty cycle is a and the load is a resistance R, the rms value of output voltage is
A:
aV
B:
a V
C:
a2V
D:
Answer: B

RMS output voltage

VL = a V.

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Current derating may be necessary when thyristors are operating in
A:
series
B:
parallel
C:
series or parallel
D:
none of the above
Answer: B

Since current does not divide equally, current derating is necessary.

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A single phase semiconverter is feeding a highly inductive load and has freewheeling diode across the load. The waveshapes of output voltage and output current
A:
are similar
B:
are not similar
C:
may be similar or dissimilar
D:
are similar only if firing angle is zero
Answer: B

When freewheeling diode conducts output current exists but output voltage is zero.

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The dynamic equalising circuit consists of a series combination of capacitor C and resistor RC across each thyristor. This resistance RC (along with parallel connected diode)
A:
limits charging current
B:
limits discharging current
C:
limits both charging and discharging currents
D:
none of the above
Answer: B

Discharge current flows through Re .

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In single phase half wave regulator, the average current over one full cycle
A:
is always positive
B:
may be positive or negative
C:
may be negative
D:
is always negative
Answer: D

The input current during positive half cycle is less than that during negative half cycle.

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