162. The device which cannot be triggered by voltage of either polarity is
A. Diac
B.Triac
C. Schotkey diode
D. SUS

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163. The maximum ? in a SGR is
A. directly proportional to Vm of supply voltage
B. inversely proportional to Vm of supply voltage
C. directly proportional to L in the circuit
D. directly proportional to L in the circuit

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164. A SCR fires at a minimum current of 80 mA and ? 65 ?C. The minimum current required to fire at 25?C is
A. > 80 mA
B. equal to 80 mA
C.< 80 mA
D. half of 80 mA

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165. An SCR is rated at 75 A peak, 20 A average. The gre astest possible delay in the trigger angle if the dc is a rated value is
A. 47.5?
B. 30? to 45?
C. 75.5?
D. 137?

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166. A SCR has an anode supply of sine voltage 200 V rms., 50 Hz applied through a 1000 resistor and fired at an angle of 60?. Assuming no voltage drop, the rms value of the output voltage is
A. 89.7 V
B. 126.7 V
C.166.7 V
D.200 Vi V

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167. A dc source of 100 V supplies a purely inductive load 0.1 H. The controller is a thyristor in series with the source and load. The latching current specified is 100 mA. The minimum width of the gating pulse to ensure thyristor turn on is
A.100
B. 100s
C. 1 ms
D.50ts

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168. A thyristor is triggered by apulse train of 5 KHz. The duty ratio is 0.4. If the allowable averaige power is 100 W. The maximum allowable gate drive power is
A. 10011 W
B. 50 W
C. 150 W
D. 250 W

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