1.
An emitter follower regulator has the following disadvantage :
2.
An SCR combines the feature of
3.
The SCR can exercise control over of ac supply.
4.
When SCR starts conducting, then ______losses all control.
5.
Turned-off time of a thyristor
7.
The use of multiphase rectifier in place of one phase rectifier results in
8.
The voltage across an SCR when it is turned on is about
9.
What is the ratio of two exponential functions of time called?
10.
Most SCRs can be turned-off by voltage reversal during negative half cycle of the ac supply for
11.
The basic difference between a series regulator and a shunt regulator is
12.
An SCR remains turned on if the anode current is more than
13.
Control system that maintains a speed voltage, or other variable within specified limits of a preset level.
14.
The di/dt protection for an SCR is achieved through the use of
15.
What is a three terminal device used to control large current to a load?
16.
In a thyristor dc chopper, which type of commutation results in best performance ?
17.
A thyristor can be termed as
18.
It is preferable to use a train of pulse of high frequency for gate triggering of SCR in order to reduce
19.
A triac can pass a portion of half cycle through the load
20.
Which one of the following is NOT the advantage of solid state switching of ac capacitors into ac supply over relay-based switching?
21.
What is a solid state equivalent of a gas filled triode?
22.
A resistor connected across the gate and cathode of an SCR
23.
When the supply voltage exceeds the breakover voltage of an SCR, it
24.
What are some areas where GTO is applicable?
25.
Turn-off time of a thyristor
26.
The shunt type regulator is suitable for which of the following?
27.
Which of the following is a four-layer diode with an anode gate and a cathode gate?
28.
When the SCR is OFF, the current in the circuit is
29.
Which device exhibits negative resistance region?
30.
R-C snubber is used in parallel with the thyristor to
31.
In a single-phase semiconverter with resistive load and for a firing angle α , each SCR conduction and freewheeling action takes place
32.
An SCR is in conducting state, a reverse voltage is applied between anode and cathode, but it fails to turn off. what could be the reason?
34.
In a singe-phase full-wave controlled bridge rectifier, minimum output voltage and maximum output voltage are obtained at which conduction angles?
35.
A thyristor has its gate current zero. To start conduction the forward voltage must exceed
36.
A single-phase full converter gives maximum and minimum output voltage at firing angles of
37.
Which one of the following is the main advantage of SMPS over linear power supply ?
38.
When the emitter terminal of a UJT is open, the resistance between the base-terminals is generally
39.
An ideal regulated power supply should have
40.
Conductivity modulation is phenomenon which occurs in
41.
Which one of the following statements regarding the two-transistor model of the p-n-p-n four-layer device is correct?
42.
Which of the following does not cause permanent damage to an SCR?
43.
Consider the following semiconductor devices:
1. Triac 2. Thyristor 3. amplifying gate thyristor
The correct sequence of these devices in increasing order of their di/dt capabilities is
44.
In a UPS, the solid state switch normally transfer supply within
46.
What is the control element in an SCR?
47.
Turn-on and turn-off times of transistor depend on
48.
Which semiconductor device acts like a diode and two transistor?
49.
When fed from a fully controlled rectifier, a dc motor, driving an active load can operate in
50.
When UJTs is turned on, the resistance between emitter terminal and lower base terminal
