251. In a three phase converter, the number of notches per cycle is____________?
A. One
B. Three
C. Six
D. Nine
252. A capacitive load in voltage source inverters generates ________________?
A. Small current spikes and can be reduced by using an inductive filter
B. Large current spikes and can be increased by using an inductive filter
C. Small current spikes and can be increased by using an inductive filter
D. Large current spikes and can be reduced by using an inductive filter
253. 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
254. The carrier which are commonly used in constant – frequency PWM is______________?
A. Sawtooth carrier
B. Inverted sawtooth carrier
C. Triangle carrier
D. All of these
255. 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
256. Double edge modulation eliminates certain harmonics when the reference is a__________?
A. Sine wave
B. Square wave
C. Triangular wave
D. Trapezoidal wave
257. 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
258. 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
259. 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
260. In a 3 phase VSI out of eight valid states, the number of valid states that produce zero ac line voltages is/are_________?
A. One
B. two
C. Three
D. Four
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