In a stud mounted SCR, the stud is in thermal contact with heat sink insulated f

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Question
In a stud mounted SCR, the stud is
Options
A. in thermal contact with heat sink
B. insulated from heat sink
C. in electrical and thermal contact with heat sink
D. in either electrical or thermal contact with heat sink

Correct Answer

in electrical and thermal contact with heat sink

Power Electronics problems

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1. Assertion (A): A GTO circuit is more compact than SCR circuit
Reason (R): A GTO can be turned off by negative gate pulse.
Options
A. Both A and R are correct and R is correct explanation of A
B. Both A and R correct but R is not correct explanation of A
C. A is correct but R is wrong
D. A is wrong but R is correct

2. A single phase half wave converter is used to charge a battery of 50 V. The thyristor is continuously fired by dc signal. Input voltage is v = V_m sin ?t. The thyristor will conduct
Options
A. from 0 to 180�
B. when v > 50 V
C. from 0 to 90�
D. When v < 50 V

3. 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
Options
A. 30�
B. 60�
C. 90�
D. 120�

4. 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
Options
A. 114�C
B. 164�C
C. 94� C
D. 84� C

5. A single phase half wave regulator uses
Options
A. 2 diodes and 2 thyristors
B. 2 thyristors
C. 1 diode and 1 thyristor
D. 2 diodes

7. In a single phase full wave regulator feeding an R-L load, the power factor angle of load is ?. The range of control of firing angle a is
Options
A. 0 ? a ? p
B. ? ? a ? p
C. 0 ? a ? (p - ?)
D. ? ? a ? (p + ?)

8. If a step down chopper is fed by a dc voltage V with T_on and T_off are on and off periods then is
Options
A. average output voltage
B. rms output voltage
C. average or rms output voltage depending on load
D. neither of the above

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