Q. An SCR is triggered at 40° in the positive half cycle only. The average anode current is 50 A. If the firing angle is changed to 80°, the average anode current is likely to be

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Q. The characteristics of a non-linear resistance is i = kv⁴. If i becomes 100 times, v becomes

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Q. In a step down chopper using pulse width modulation, Ton = 3 x 10¯³ and Toff = 1 x 10¯³ s. The chopping frequency is

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Q. Thyristors are suitable for dc circuit breakers but not for ac circuit breakers.

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Q. Assertion (A): Inverters and choppers use fast switching thyristors

Reason (R): Fast switching SCR has low turn off time.

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Q. The number of leads in an SCR are :

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Q. A thyristor has a turn on time of 6 μs. If the anode circuit is inductive, the turn on time will be

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Q. The total number of leads in reverse conducting thyristor is

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Q. Assertion (A): A TRIAC is a bidirectional SCR.

Reason (R): A TRIAC is a four layers 3 terminal device and can conduct in both directions.

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Q. The value of capacitor C for dynamic equalising circuit of series connected thyristors is determined by

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Q. A chopper

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Q. 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.

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Q. In a single phase full wave regulator, the firing angles in the positive and negative half cycles are generally

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Q. An electric heater is controlled by thyristors through on-off control. If α = 0.4, the heating is

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Q. A single phase half wave controlled rectifier circuit has a free wheeling diode. The load is a combination of R and L. The firing angle is α. The period of conduction of SCR and free wheeling diode respectively are

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Q. Assertion (A): A transistor requires a continuous base signal for conduction but a thyristor requires a gate pulse.

Reason (R): Transistor find widespread application in power electronic circuits.

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Q. In a thyristor the gate current is increased, then

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Q. Thyristors are not suitable for logic circuits.

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Q. In a circuit using a full wave converter (M - 2 connection) the PIV of each thyristor is 400 V. For the same output voltage and fully controlled bridge converter, PIV will be

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Q. A dc separately excited motor has constant field current. The armature is fed from a single phase supply through a full converter. When α = 0, speed is 500 rpm. If α = 45°, the speed is likely to be

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