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Electrical Engineering (EE) Exam  >  Electrical Engineering (EE) Test  >  Topicwise Question Bank for Electrical Engineering  >  Test: Three Phase Converters - 2 - Electrical Engineering (EE) MCQ

Three Phase Converters - 2 - Free MCQ Practice Test with solutions, GATE


MCQ Practice Test & Solutions: Test: Three Phase Converters - 2 (20 Questions)

You can prepare effectively for Electrical Engineering (EE) Topicwise Question Bank for Electrical Engineering with this dedicated MCQ Practice Test (available with solutions) on the important topic of "Test: Three Phase Converters - 2". These 20 questions have been designed by the experts with the latest curriculum of Electrical Engineering (EE) 2026, to help you master the concept.

Test Highlights:

  • - Format: Multiple Choice Questions (MCQ)
  • - Duration: 20 minutes
  • - Number of Questions: 20

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Test: Three Phase Converters - 2 - Question 1
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A three-phase full converter supplied from a 230 V source is working as a line commutated inverter. The load consists of RLE type with R = 5 Ω, E = 200 V and L = 1 mH. A continues current of 10 A is flowing through the load, find the value of the firing angle delay.

Detailed Solution: Question 1

Vo = 200 – 10×5 = 150V as the circuit is operating as an inverter Vo = -150V
Now, Vo = (3Vml/π) cos α
α = cos-1(-150π/3√2×230) = 118.88°.

Test: Three Phase Converters - 2 - Question 2
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 A three-phase full converter is driving a DC motor. If a continues current of Im amperes is flowing through the motor load, then find the rms value of supply current drawn by the converter to drive the motor.

Detailed Solution: Question 2

The RMS value of the supply current IS over π radians would be
(IS)2 = (1/π) x (Im)2 x (2π/3) = Im√2/√3.

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Test: Three Phase Converters - 2 - Question 3
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Name the below given circuit.

Detailed Solution: Question 3

 It uses 3 SCRs and 3 diodes, hence it is a semi-converter. Option (b) and (d) make no sense, because there can be no full controlled semi-converter.

Test: Three Phase Converters - 2 - Question 4
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In the below given circuit, each SCR and diode conduct for

Detailed Solution: Question 4

 At any given time, one SCR and one diode is conducting, each conduct for 120° per cycle.

Test: Three Phase Converters - 2 - Question 5
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In the below given circuit, __ and __ conduct along with T2.

Detailed Solution: Question 5

When one SCR conducts, a diode conducts along with it at a time to provide the path of current flow. . For example, if T2 starts conducting at 90° it will conduct till 90+120 = 210°. But while T2 is conducting, half of the time i.e. from 90 to 150 D1 is conducting and another half of the time D3 is conducting. T2 and D2 cannot conduct together as it will cause a short circuit. Hence, T2-D1 conduct for 60° and then T2-D3 conduct for another 60°.

Test: Three Phase Converters - 2 - Question 6
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In a 3 – φ semi converter, for firing angle equal to 125° and extinction angle equal to 105°, each SCR and freewheeling diode conduct respectively for

Detailed Solution: Question 6

For 3 – φ semi converter, for α = 125o , thyristor and diode conducts for 55o only. Freewheeling diode conducts for 105o – 55o = 50o .

Test: Three Phase Converters - 2 - Question 7
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A three phase Bridge rectifier as shown.

Which is more suitable sequence of operation for maximum out put

Detailed Solution: Question 7

For maximum output at a time two phases conducts and each set conducts for 360/6 and each diode 360/3 degree

Test: Three Phase Converters - 2 - Question 8
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A 3-phase full converter feeds power to an R load of 10 Ω. For a firing angle delay of 30° the load takes 5 kW. An inductor of large value is also connected to the load to make the current ripple free. Find the value of per phase input voltage.

Detailed Solution: Question 8

 Ior = Vo/R = (3Vml/Rπ) cos α
P = 5 kW = Ior2 x R = [(3Vml/π) cos α]2 x 1/R] Therefore, Vs (line) = √50000 x (π/√2 x 3 x cos30) = 191.22 V
Vs (phase) = 191/√3 V.

Test: Three Phase Converters - 2 - Question 9
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A three-phase semi-converter circuit is given a supply of 400 V. It produces at the output terminals an average voltage of 381 V. Find the rectification efficiency of the converter circuit.

Detailed Solution: Question 9

Rectification efficiency = Pdc/Pac
Pdc = Vo x Io . . . (both average values of output current and voltage)
Pac = Vrms x Irms . . . (both rms values of input current and voltage)
For a semi-converter Irms = Io
Therefore, Rectification efficiency = 381/400 = 95.25 %.

Test: Three Phase Converters - 2 - Question 10
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In a 3-phase semi-converter, for firing angle less than 60° the freewheeling diode conducts for

Detailed Solution: Question 10

 In case of a semi-converter operating with α < 60°, FD does not comes into play, as the voltage never falls to zero and gives no chance for the inductor to discharge.

Test: Three Phase Converters - 2 - Question 11
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In a 3-phase full wave converter, if V is the maximum value of line voltage at the input, then each SCR is subjected to a peak negative voltage of

Detailed Solution: Question 11

PIV = √3 Vml in case of a semi-converter.

Test: Three Phase Converters - 2 - Question 12
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A three phase full converter is supplying a purely resistive load at 400V d.c. for 30° firing angle. The output
voltage for 90° firing angle would be 

Detailed Solution: Question 12

Average output voltage of 3 – Φ full converter

Test: Three Phase Converters - 2 - Question 13
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The effect of source inductance on the performance of a 3-phase controlled converter is to

Detailed Solution: Question 13

 It reduces the average value of the output voltage by introducing a overlap delay μ.

Test: Three Phase Converters - 2 - Question 14
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Which of the following converter circuits would require a neutral point?

Detailed Solution: Question 14

Half wave converter would require delta-star transformer, the secondary winding star connection requires a neutral point.

Test: Three Phase Converters - 2 - Question 15
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A 12 pulse rectifier output generated with minimum and maximum value of _________

Detailed Solution: Question 15


Vmin = Vm sin(90 - 15) = 0.9659 Vm
Vmax = Vm sin90 = Vm.

Test: Three Phase Converters - 2 - Question 16
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 A 3-phase bridge converter is given a three-phase supply in the phase sequence R-Y-B. Let the neutral to R phase voltage be Vm sinωt. The first SCR (connected to R phase) is fired at an angle of 15°. What is the maximum value at the output terminals at this instant?

Detailed Solution: Question 16

In case of a 3 phase bridge converter, the maximum value of voltage at the output terminal is always 1.5 Vm.

Test: Three Phase Converters - 2 - Question 17
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The PIV experienced by each SCRs in M-3 converter is __________ times that in a 3-phase full converter having the same output voltage.

Detailed Solution: Question 17

 In case of M-3 type of connection, the devices have to handle more peak inverse voltage (PIV) than the 3-phase full converter which has 6 SCRs.

Test: Three Phase Converters - 2 - Question 18
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In a 3φ converter and inverter circuit as shown in figure Vs = 400 V

Detailed Solution: Question 18



= 3555.55 W
Total power = 3 × 3555.55
= 10.67 KW

Test: Three Phase Converters - 2 - Question 19
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A 3-phase full converter has an average output voltage of 365 V for zero degree firing and resistive load. For a firing angle of 90 degree, the output voltage would be

Detailed Solution: Question 19

Cos 90 = 0.

Test: Three Phase Converters - 2 - Question 20
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 Semi-converters are

Detailed Solution: Question 20

Semi-converters are single quadrant converters, because the voltage and current can only be both positive due to the diodes connected.

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About this Electrical Engineering (EE) Practice Test

This test contains 20 MCQs on Three Phase Converters - 2 with detailed solutions for each question. It is part of the Topicwise Question Bank for Electrical Engineering course on EduRev, designed to align with the current Electrical Engineering (EE) syllabus. Each solution explains not just the correct answer but also gives you an understanding of the topic — not just to attempt the question but also help you prepare for the exam with practice.

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