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Test: Three Phase Rectifiers


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20 Questions MCQ Test Power Electronics | Test: Three Phase Rectifiers

Test: Three Phase Rectifiers for Electrical Engineering (EE) 2022 is part of Power Electronics preparation. The Test: Three Phase Rectifiers questions and answers have been prepared according to the Electrical Engineering (EE) exam syllabus.The Test: Three Phase Rectifiers MCQs are made for Electrical Engineering (EE) 2022 Exam. Find important definitions, questions, notes, meanings, examples, exercises, MCQs and online tests for Test: Three Phase Rectifiers below.
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Test: Three Phase Rectifiers - Question 1

In a three-phase half wave rectifier usually, the primary side of the transformer is delta connected because

Detailed Solution for Test: Three Phase Rectifiers - Question 1

The delta connected winding help circulating and eliminating the triplen (3rd order) harmonics.

Test: Three Phase Rectifiers - Question 2

The diode rectifier circuit given below is that of a

Detailed Solution for Test: Three Phase Rectifiers - Question 2

 Common anode arrangement because all the anodes are connected to the load side.

Test: Three Phase Rectifiers - Question 3

 In a three-phase half wave diode rectifier using 3 diodes, each diode conducts for

Detailed Solution for Test: Three Phase Rectifiers - Question 3

Each diode conducts for 120 degrees, starting from ωt = 30 degrees.

Test: Three Phase Rectifiers - Question 4

In the below shown diode rectifier circuit,

The diodes D1, D2 & D3 are connected to phases R,Y and B respectively as shown
The phase sequence is R-Y-B.
The diode D1 would conduct from

Detailed Solution for Test: Three Phase Rectifiers - Question 4

 It conducts from 30 to 150, for 90 degrees. D1 starts conducting first as it will be the most positive as it is connected to the R phase.

Test: Three Phase Rectifiers - Question 5

In the below shown diode rectifier circuit,

The diodes D1, D2 & D3 are connected to phases R,Y and B receptively as shown
The phase sequence is R-Y-B.
The diode D3 conducts from

Detailed Solution for Test: Three Phase Rectifiers - Question 5

It conducts from 270 to 450, for 120 degrees. D1 starts conducting first (from 30 degrees) as it will be the most positive as it is connected to the R phase & likewise.

Test: Three Phase Rectifiers - Question 6

In a three-phase half wave diode rectifier using 3 diodes,

Detailed Solution for Test: Three Phase Rectifiers - Question 6

3 diodes, each conduct for 120 degree at a time.

Test: Three Phase Rectifiers - Question 7

 In a three-phase half wave diode rectifier, if Vmp is the maximum phase voltage, then the output voltage on a R load varies from

Detailed Solution for Test: Three Phase Rectifiers - Question 7

The voltage value is positive and varies from (1/2)Vmp to Vmp.

Test: Three Phase Rectifiers - Question 8

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

Detailed Solution for Test: Three Phase Rectifiers - Question 8

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.

Test: Three Phase Rectifiers - Question 9

In a three-phase half wave 6-pulse mid-point type diode rectifier, each diode conducts for

Detailed Solution for Test: Three Phase Rectifiers - Question 9

In a six-pulse rectifier, each diode conducts once every one cycle, 60° x
6 diodes = 360°.

Test: Three Phase Rectifiers - Question 10

 A step-down delta-star transformer, with per-phase turns ration of 5, is fed from a 3-phase, 1100 V, 50 Hz source. The secondary of this transformer through a 3-pulse type rectifier feeds a R load of 10 Ω. Find the maximum value of the load current (phase).

Detailed Solution for Test: Three Phase Rectifiers - Question 10

Vph = 1100/5 = 220 V (Transformer ratio = 5)
Vmp = √2 x 220 V
Imp = Vmp/R.

Test: Three Phase Rectifiers - Question 11

 A step-down delta-star transformer, with per-phase turns ratio of 5 is fed from a 3-phase 1100 V, 50 Hz source. The secondary of this transformer is connected through a 3-pulse type rectifier, which is feeding feeding an R load. Find the average value of output voltage.

Detailed Solution for Test: Three Phase Rectifiers - Question 11

Vph = 1100/5 = 220 V (Transformer ratio = 5)
Vmp = √2 x 220 V
Vo = 3√3/2π x Vmp = (√2 x √3 x 3 x 220)/(2 x π).

Test: Three Phase Rectifiers - Question 12

The circuit shown below is that of a

Detailed Solution for Test: Three Phase Rectifiers - Question 12

 A 3-phase, 6-pulse rectifier consists of 6 diodes connected in 3 legs. Two diodes conduct at a time.

Test: Three Phase Rectifiers - Question 13

A step-down delta-star transformer, with per-phase turns ratio of 5 is fed from a 3-phase 1100 V source. The secondary of this transformer is connected through a 3-pulse type rectifier, which is feeding an R load.
The power delivered to the load is 6839.3 Watts.
The maximum value of the load current is √2 x 22 A.
Fin, the rms value of output voltage Vo (rms)

Detailed Solution for Test: Three Phase Rectifiers - Question 13

Power delivered to the load (Pdc) = Vo(rms)2/R (i)
Imp = Vmp/R
Therefore, R = Vmp/Imp = (1100 x √2)/(5 x √2 x 22) = 10 Ω
Put R in equation (i) & find the required R.M.S voltage.

Test: Three Phase Rectifiers - Question 14

 From the diode rectifier circuit shown below, with phase sequence R-Y-B, diodes D3 & D5 conduct when

Detailed Solution for Test: Three Phase Rectifiers - Question 14

 Which diode will conduct depends on where is it in connected? as in in which phase?. D3’s anode is connected to the R phase, hence it will turn on when R is the most positive.

Test: Three Phase Rectifiers - Question 15

From the diode rectifier circuit shown below, with phase sequence R-Y-B, from ωt = 150° to 270°

Detailed Solution for Test: Three Phase Rectifiers - Question 15

 Construct the phase voltage waveforms on a graph. At 150 degree, D2 is forward biased while the other positive group diodes i.e. D2 and D3 remain reserved biased.

Test: Three Phase Rectifiers - Question 16

A 3-phase 6-pulse diode rectifier is shown below with phase sequence R-Y-B. The negative group of diodes (D4, D5, D6) conduct in sequence (from ωt = 0°)

Detailed Solution for Test: Three Phase Rectifiers - Question 16

 The conduction sequence always depends on the phase sequence, which diode is conducting will depend upon which phase voltage is active at that moment.

Test: Three Phase Rectifiers - Question 17

 For a 3-phase 6-pulse diode rectifier, has Vml as the maximum line voltage value on R load. The peak current through each diode is

Detailed Solution for Test: Three Phase Rectifiers - Question 17

Two diodes conduct at a time, constructing the equivalent circuit with supply, R & replacing the conducting diodes by S.C & non-conducting as O.C, the required value can be found out.

Test: Three Phase Rectifiers - Question 18

A 3-phase bridge rectifier, has the average output voltage as 286.48 V. Find the maximum value of line voltage

Detailed Solution for Test: Three Phase Rectifiers - Question 18

Vo = 3Vml/π
Vml = (π x Vo)/3 = 300 V.

Test: Three Phase Rectifiers - Question 19

A 3-phase bridge rectifier charges a 240 V battery. The rectifier is given a 3-phase, 230 V supply. The current limiting resistance in series with the battery is of 8 Ω.
Find the average value of battery charging current.

Detailed Solution for Test: Three Phase Rectifiers - Question 19

Vo = (3√2 x 230)/π = 310.56 V
Draw the battery charging circuit,
Vo = E + (Io x R)
Io = (Vo – E)/R = (310.56 – 240)/8.

Test: Three Phase Rectifiers - Question 20

A 3-phase bridge rectifier charges a 240-V battery. The rectifier is given a 3-phase 230 V supply. The current limiting resistance in series with the battery is 8 Ω.
Find the power delivered to the battery (Pdc).

Detailed Solution for Test: Three Phase Rectifiers - Question 20

 Vo = (3√2 x 230)/π = 310.56 V
Draw the battery charging circuit,
Vo = E + (Io x R)
Io = (Vo – E)/R = (310.56 – 240)/8 = 8.82A
Pdc = 240 x 8.82 = 2116 W.

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