The average value of the output voltage, in a 3-phase half wave diode rectifier with Vml as the maximum line voltage value, is given by the expression

A)
Vml/3π
B)
2Vml/3π
C)
3Vml/2π
D)
3Vml

Correct Answer : Option (C) :   3Vml/2π

Explanation : The average value can be obtained by
3 x [ 1/2π x Vml sin ωt d(ωt) ]
The integration runs from π/6 to 5π/6 as the diode is conducting for 120 degrees each.

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Static UPS requires ______
A)
only rectifier
B)
only inverter
C)
both inverter and rectifier
D)
None of the above

Correct Answer :   both inverter and rectifier

Explanation : Rectifier to converter the dc from the battery to ac. Inverter to charge the battery from mains.

HVDC transmission has ___________ as compared to HVAC transmission.
A)
higher corona loss
B)
smaller transformer size
C)
smaller power transfer capabilities
D)
smaller conductor size

Correct Answer :   smaller conductor size

Explanation : The conductor size is smaller as there is no sink effect, and the whole conductor is utilized for transmitting power.

SPMS are based on the ________ principle.
A)
MOSFET
B)
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C)
Phase control
D)
Integral control

Correct Answer :   Chopper

Explanation : SMPS (Switching mode power supply) are based on the chopper principle. The output dc voltage is controlled by varying the duty cycle of the chopper circuit.

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