Three phase DC - AC inverters - Electrical Engineering (MCQ) questions and answers

1)   In a 3 phase CSI, if the required line output voltages are balanced and 120 degree out of phase, then the chopping angles are used to eliminate only the harmonics at frequencies

a. 5
b. 7
c. 11
d. All of these
Answer  Explanation 

ANSWER: All of these

Explanation:
No explanation is available for this question!


2)   For similar carrier and modulating signals, the line current used in CSI is

a. Identical to line voltage in a VSI
b. Identical to line current in VSI
c. Identical to phase voltage in VSI
d. Identical to phase voltage in CSI
Answer  Explanation 

ANSWER: Identical to line voltage in a VSI

Explanation:
No explanation is available for this question!


3)   Under harmonic free load voltages, the 3 phase VSI

a. Does not contains second harmonic
b. Does not contains third harmonic
c. Does not contains fifth harmonic
d. Does not contains seventh harmonic
Answer  Explanation 

ANSWER: Does not contains second harmonic

Explanation:
No explanation is available for this question!


4)   The square wave operation of 3 phase VSI lines contains the harmonics. The amplitudes are

a. Directly proportional to their harmonic order
b. Inversely proportional to their harmonic order
c. Not related to their harmonic order
d. None of these
Answer  Explanation 

ANSWER: Inversely proportional to their harmonic order

Explanation:
No explanation is available for this question!


5)   In a square - wave operation of 3 phase CSIs, the power values are on for

a. 60 degree
b. 90 degree
c. 120 degree
d. 150 degree
Answer  Explanation 

ANSWER: 120 degree

Explanation:
No explanation is available for this question!


6)   A carrier based PWM technique in CSI is composed of

a. A switching pulse generator and a shorting pulse generator
b. A shorting pulse distributor
c. A switching and shorting pulse combination
d. All of these
Answer  Explanation 

ANSWER: All of these

Explanation:
No explanation is available for this question!


7)   In square wave operation mode of 3 phase VSI, the VSI

a. Can control the load voltage
b. Cannot control the load voltage
c. Cannot control the load voltage except by means of dc link voltage
d. Cannot control the load voltage except by means of dc link current
Answer  Explanation 

ANSWER: Cannot control the load voltage except by means of dc link voltage

Explanation:
No explanation is available for this question!


8)   In a 3 phase VSI SPWM to use a single carrier signal and preserve the features of PWM technique, the normalized carrier frequency should be

a. Multiple of two
b. Odd multiple of three
c. Odd multiple of five
d. Odd multiple of seven
Answer  Explanation 

ANSWER: Odd multiple of three

Explanation:
No explanation is available for this question!


9)   In a three phase voltage source inverters

a. Only amplitude of voltage is controllable
b. Only phase is controllable
c. Both amplitude and phase is controllable
d. Amplitude, phase and frequency of voltages should always be controllable
Answer  Explanation 

ANSWER: Amplitude, phase and frequency of voltages should always be controllable

Explanation:
No explanation is available for this question!