Assertion (A): If the duty cycle of chopper is low the current would not become discontinuous
Reason (R): If the time constant L/R of the load in chopper is low the current may become discontinuous.
Answer: C
If duty cycle is low, current may become discontinuous.
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The average load current supplied by a thyristor depends on
Answer: A
The firing angle controls the period of conduction and hence average load current.
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A 3 phase ac regulator uses
Answer: B
Two thyristors for each phase.
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A single phase half wave converter is feeding a resistive load. Just before triggering, the voltage across thyristor is
Answer: C
Before triggering the whole of applied voltage is across SCR and load current is zero.
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A cycloconverter is
Answer: D
It changes ac at frequency f into ac at a frequency different from f.
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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
Answer: B
When freewheeling diode conducts output current exists but output voltage is zero.
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A 750 A circuit uses thyristor of current rating 175 A. If derating is 25%, the number of thyristors in parallel is
Answer: C
No explanation.
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A single phase step up cycloconverter changes 50 Hz to 100 Hz. Then one half wave of input will give rise to
Answer: B
Since output frequency is 2f, one half wave of input must equal one full wave of output.
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A single phase semiconverter has a freewheeling diode. If the firing angle is a and the load is purely resistive, the periods of conduction and freewheeling respectively are
Answer: A
Freewheeling diode conducts only when load is inductive. If load is purely resistive free wheeling diode does not come into operation.
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In a fully controlled bridge converter feeding a resistive load the waveshapes of output voltage and output current
Answer: A
For resistive load output current is always proportional to output voltage.
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