Test: Advance Three Phase Converters


10 Questions MCQ Test Power Electronics | Test: Advance Three Phase Converters


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Attempt Test: Advance Three Phase Converters | 10 questions in 10 minutes | Mock test for Electrical Engineering (EE) preparation | Free important questions MCQ to study Power Electronics for Electrical Engineering (EE) Exam | Download free PDF with solutions
QUESTION: 1

In a 3 phase M-6 controlled converter for continuous conduction mode, each SCR conducts for __________ per cycle.

Solution:

Each SCR conducts for 60° or 2π/6 radians. 6 x 60 = 360°.

QUESTION: 2

 In a 3 phase, 12-pulse controlled converter for continuous conduction mode, each SCR conducts for __________ per cycle.

Solution:

Each SCR conducts for 30° or π/6 radians. 12 x 30 = 360°.

QUESTION: 3

A 3-phase full converter delivers a ripple free load current of 10 A with a firing angle delay of 45°. The input voltage is 3-phase, 400 V, 50 Hz. The source current is given by the following relation.

Find the fundamental component of the source current amplitude.

Solution:

Put n = 1 (fundamental component) and the rest of the given values in the above given equation.

QUESTION: 4

A 3-phase full converter delivers a ripple free load current of 10 A with a firing angle delay of 45°. Find the DF.

Solution:

 DF = cosα = cos45 = 0.707
Note that ripple free current does not mean that DF = 0. It means the current is continues in magnitude and direction, current will always contain harmonics (distortions) whether it is rippled or ripple free.

QUESTION: 5

What is the relationship between DF, CDF and PF?

Solution:

PF (power factor) = (distortion factor) x (current distortion factor).

QUESTION: 6

The commutation period when both incoming and outgoing SCRs are conducting due to source inductance is called as the

Solution:

Due to source inductance, SCRs cannot start and stop conducting immediately, hence a time occurs when both incoming and outgoing SCRs are conducting together. This delay is called as commutation angle or overlap period (μ).

QUESTION: 7

A 3-phase full converter delivers a ripple free load current of 10 A with a firing angle delay of 45°. The input voltage is 3-phase, 400 V, 50 Hz. The source current is given by the following relation.


Find the value of 2nd harmonic source current amplitutue.

Solution:

2nd harmonics are absent in a 3-phase full converter, it has only odd number of harmonics i.e. 3rd, 5th etc.

QUESTION: 8

In a p-pulse converter, each SCR conducts for (per cycle)

Solution:

 In a p-pulse controlled converter, each device conducts for p radians. p-pulse converter would have p devices. Hence, 2π/p x p = 2π = 360°.

QUESTION: 9

Which of the below mentioned converter can operate in both 3-pulse and 6-pulse modes?

Solution:

Semi-converters can operate in 6-pulse modes gating the SCRs at appropriate intervals.

QUESTION: 10

 A M-6 controlled converter or 6-pulse half-wave controlled converter is obtained by using a transformer having

Solution:

M-6 requires a transformer having a delta connected primary and a double star connected secondary such that 6 SCRs are connected to it on the secondary side.

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