Q. A cycloconverter cannot give a frequency higher than input frequency.

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Q. A thyristor has internal power dissipation of 40W and is operated at an ambient temperature of 20°C. If thermal resistance is 1.6° C/W, the junction temperature is

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Q. In a single phase dual converter, α1, and α2 are firing angles of the two converters. Then

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Q. The number of gates in an SCR is

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Q. The waveshape of output voltage of half bridge inverter is

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Q. A 3 phase induction motor is controlled by voltage and frequency control such that the ratio V/f is constant. At 50 Hz, the speed is 1440 rpm. At 25 Hz, the speed is likely to be

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Q. The gate current required to turn on an SCR is

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Q. Assertion (A): A high dv/dt may cause triggering of a thyristor.

Reason (R): A high dv/dt results in charging current in the thyristor.

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Q. Assertion (A): When an SCR is conducting, the voltage drop across is about 1 V.

Reason (R): When an SCR is conducting, the junction temperature is about 200°C.

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Q. When the core of a saturable reactor is saturated, the inductance is high.

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Q. In controlled heating circuits, thyristors act as

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Q. In a fully controlled bridge converter feeding a resistive load the waveshapes of output voltage and output current

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Q. Assertion (A): A GTO circuit is more compact than SCR circuit

Reason (R): A GTO can be turned off by negative gate pulse.

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Q. In a single phase full wave ac regulator, the firing angles in the two half cycles

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Q. As regards single phase dual converter

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Q. In a semi converter feeding a resistive load, the firing angle is α. Each thyristor conducts for

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Q. Between which points does UJT exhibit negative resistance characteristics

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Q. A thyristor has maximum allowable junction temperature of 110° C and the ambient temperature is 40°C, If the maximum internal power dissipation is 50 W, the thermal resistance is

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Q. A single phase electric heater uses phase controlled thyristors. The firing angle is 90°. The degree of heating is

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Q. Which of these commutation methods is used in AC-DC converters?

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