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

View solution

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

View solution

Q. The number of gates in an SCR is

View solution

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

View solution

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

View solution

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

View solution

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.

View solution

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.

View solution

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

View solution

Q. In controlled heating circuits, thyristors act as

View solution

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

View solution

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

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

View solution

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

View solution

Q. As regards single phase dual converter

View solution

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

View solution

Q. Between which points does UJT exhibit negative resistance characteristics

View solution

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

View solution

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

View solution

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

View solution

Q. In a 3 phase semiconverter, the dc output voltage for a certain firing angle is 50% of the maximum possible value. The firing angle is

View solution