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MCQs 1: If a shunt motor is started with its field winding open then?

It will rotate at the same speed as that with its field winding closed It will rotate at less speed as that with its field winding closed It will rotate at dangerously high speed None of these
Answer Explanation

MCQs 2: A rectifier with an external low pass filter is an example of______________?

Indirect switch matrix circuits Direct switch matrix circuits Embedded converters All of these
Answer Explanation

MCQs 3: The power demand can be estimated approximately by___________?

Load survey method Mathematical method Statistical method Economic parameters
Answer Explanation

MCQs 4: 4 thyristors rated 200 V in series. The operating voltage of the string is 600 V. Derating factor of the string is_____________________?

0.75 0.7 0.2 0.25
Answer Explanation

MCQs 5: Unipolar modulation is generally used in____________?

AC – AC converters AC – DC converters DC – AC converters DC – DC converters
Answer Explanation

MCQs 6: Dynamic equalizing circuit is used for________________?

equal division of voltage across each thyristor equal division of current through each thyristor in parallel equal division of voltage across each thyristor in parallel equal division of current through each thyristor in series
Answer Explanation

MCQs 7: A string of n parallel SCRs is operated at 72 KA, the rating of each SCR is 1 KA. If derating factor of the string is 0.1. value of n will be___________?

60 70 80 90
Answer Explanation

MCQs 8: 60 thyrsistors are connected in series and parallel to form a 10 KV and 5.5 KA switch. Each thyristor is rated for 1.2 KV, 1 KA. The no. of parallel path are 6. The efficiency of the switch is______________________?

76.3 % 91.6 % 83.3 % 90.9 %
Answer Explanation

MCQs 9: Maximum di / dt in a SCR is________?

Directly proportional to Vm of supply voltage Inversely proportional to Vm of supply voltage Inversely proportional to L in the circuit Both A and C
Answer Explanation

MCQs 10: A thyristor string is made of a no. of SCR connected in series and parallel. The string have volume and current of 11 KV and 4 KA. The voltage and current rating of available SCRs are 1800 V and 1000 A. For a string efficiency of 90 % let the number of SCRs in series and parallel are a and b respectively. Then the value of a and b will be_____________?

5, 7 4, 6 7, 5 6, 4
Answer Explanation

MCQs 11: For series connected SCR’s dynamic equalising circuit consists of___________?

R and C in series but with diode across C R and C in series but with diode across R Series R and diode with C across R Series R and diode with C across R
Answer Explanation

MCQs 12: By which one of the following we can measure the reliability of a string_____________?

String efficient Reliability factor Factor of safety Derating factor
Answer Explanation

MCQs 13: Anode current in an SCR consists of____________?

holes only electrons only either electron or holes Both electron and holes
Answer Explanation

MCQs 14: To meet high current demand we use SCRs in______________?

series connection parallel connection anti parallel connection both B and C.
Answer Explanation

MCQs 15: Dynamic equalising circuit is useful____________?

To limit di / dt of SCR To limit dV / dt of SCR For voltage equalisation Both B and C
Answer Explanation

MCQs 16: SCRs are used in series to meet_______________?

high current demand low voltage demand low current demand high voltage demand
Answer Explanation

MCQs 17: Which following is a two terminal three layer device?

BJT Power dioed MOSFET None of above
Answer Explanation

MCQs 18: ON state voltage drop across SCR lie between the range_____________?

0 – 0.5 V. 0.5 – 1 V. 1 – 1.5 V. 1.5 – 2 V.
Answer Explanation

MCQs 19: Which of following is not a power transistor?

IGBTs COOLMOS TRIAC SITS
Answer Explanation

MCQs 20: Which statement is true ?

Reverse recovery time ( trr ) > gate recovery time (tgr) Device turn OFF time ( tq ) > reverse recover time (trr) Circuit turn OFF time > device turn OFF time ( tq ) All of these
Answer Explanation

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