1. a) Explain the term PWM b) Explain why PWM keeps the switching frequency constant. C) Explain the term Buck, Boost an

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1 A Explain The Term Pwm B Explain Why Pwm Keeps The Switching Frequency Constant C Explain The Term Buck Boost An 1 (48.86 KiB) Viewed 24 times

1. a) Explain the term PWM b) Explain why PWM keeps the switching frequency constant. C) Explain the term Buck, Boost and Buck-Boost converters. d) Explain the term duty cycle. e) For what purpose burst controlled AC regulator is used? 1) Explain the internal structure of a Universal Motor. 3) What are the applications of Universal Motors? Explain the reason for the selection of the Universal Motors instead of the series DC motors. 2. A burst controlled AC regulator is feeding a 200 ohm resistive load. The AC supply providing 240 Vrms voltage at 60Hz. a) For one cycle on, four cycles of control calculate the load res voltage current, power transferred to the load and efficiency b) For four cycles on, one cycle of control calculate the load rms voltage, current power transferred to the load and efficiency. 3. A firing angle controlled triac is feeding a resistive load of 125 ohm. The AC supply providing 220 Vrms voltage at 50Hz. a) For firing angle 35 degrees calculate the load rms voltage, current, power transferred to the load and efficiency. b) For firing angle 135 degrees calculate the load em voltage current, power transferred to the load and efficiency. 4. A firing angle controlled triac is feeding a RL load with L-16 mH and R-12 ohm. The tric input voltage is 220 Vrms and 50 Hz a) Calculate the minimum firing angle at which triac can be fired b) If firing angle is 27 degress find the angle B at which zero current occurs. c) Find the current 5 msec after firing. 5. Abuck converter has a 170 DC source and feeds a resistive load of 50 chens.. Determine the average power transferred to the load when: a) Converter on and off times are equal and 1 msec. b) Converter on time is 3 msec and off time is 1 msec. c) Calculate the duty cycle and output frequency for each case d) Calculate the rms power transferred to the load for the same cases. 6. A d.c. to d.c. truck converter has an inductive load of 1,5ohm resistance and 15mH inductance. Source voltage is 967. The frequency of the chopper is set to 200Hz and the duty cycle is 52%. Determine the average, maximum and minimum load currents. a) Draw the output voltage and current. b) Calculate average output voltage, current and power transferred to the load. c) Calculate the land I, current values (minimum and maximum current levels of the load). d) Calculate the rms value of the load current and rm value of power transferred to the load. 7. A universal motor is driven by a single thyristor from an AC supply of 220V at 50Hz. Total field and armature resistance of the motor is 180 Armature voltage constant is 0.79 V/rad/s for saturated operation Determine the average motor current and torque when the speed is 650 rev/min, firing angle delay is 35 degrees and the conduction angle is 180 degrees