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Assertion (A): The principal of step-up chopper can be employed for the regenerative braking of dc motors.
Reason (R) : The step-up chopper can be employed in regenerative braking only for increasing motor speeds
A dc chopper has a T0N of 1 ms and its frequency is 500 Hz. What will be its duty cycle?
An RLE load is operating in a chopper circuit from a 500 volts dc source as shown in figure
For the load, L = 0.06H, R=0 Ω an duty cycle of 0.2, what is the chopping frequency to limit the amolitude of load current excursion to 10 A?
Match List-I (Thyristor chopper circuits) wtih List-ll (Characteristics) and select the correct answer using the codes given below the lists:
List-I
A. Current commutated chopper
B. Voltage commutated chopper
C. Load commutated chopper
List-ll
1. Diode in antiparallel with main SCR
2. Used in high power circuits
3. No requirement of any commutating inductor
If T is the chopping period, Ton the on-time period of chopper and Toff the off-time period of the chopper, then consider the following statements associated with the methods of controlling the output voltage of a chopper:
1. In pulse-width modulation (PWM) scheme, T is kept constant while Ton is varied.
2. In variable-frequency modulation (VFM) scheme, T is varied while either of Ton or Toff is kept constant.
3. In PWM scheme, the output voltage can be varied between zero to source voltage.
4. The large Toff in VFM scheme may make the load current discontinuous
5. PWM scheme is better than VFM scheme.
Which of the statements given above are correct?
In dc choppers, the waveforms for input and output voltages are respectively
A class C chopper is operated from a 220 V battery. The load Is a dc motor with R = 0.1Ω, L= 10 mH and Eb= 100 V. The duty cycle of the chopper to achieve regenerative braking at the rated current of 10 Ampere would be equal to
Assertion (A) : In dc choppers, it is essential to provide a separate commutation circuitry to commutate the main power SCR.
Reason ( R ) : A chopper is dc equivalent to an ac transformer having continuously variable turns ratio.
23 docs|285 tests
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23 docs|285 tests
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