B.Tech-B.Tech Electrical Engineering 6th Sem 6EE4 Advanced power Electronics (Common for EE And EX) 6E3112(Rajasthan Technical University-2011)
6E3112
B. Tech VI Semester (Main) Examination, May/June - 2011
Electrical Engineering
6EE4 Advanced power Electronics (Common for EE And EX)
Time : 3 Hours
Maximum Marks: 80
Min. Passing Marks : 24
Unit - I
Q.1. a) What is an ac voltage controller? List some of its industrial applications. Enumerate its merits and demerits. [8]
b) For a single phase ac voltage controller feeding a resistive load, show that power factor is given by expression [1/π {(π - a) +1/2 Sin 2a}] 1/2 . [8]
OR
Q.2. a) Discuss the operation of a single phase ac voltage controller with RL load when firing angle (α) is less than, or equal to, load phase angle (Φ). Hence show that for a less than Φ, output voltage of the ac voltage controner cannot be regulated. [8]
b) A single phase AC voltage controller feed power to a resistive load of 3Ω from 230 V, 50 Hz soutce, calculate [8]
i) The maximum values of average and rills thyristor currents for any firing angle (α).
ii) The minimum turn off time for any firing angle α.
iii) Ratio of third harmonic voltage to fundamental voltage for α =π/3.
Unit - II
Q.3. a) State different method of voltage control in inverters. Describe PWM control in inverters. [8]
b) Draw the schematic of a three phase current source inverter and describe its operation. [8]
OR
Q.4. a) Describe the operation of 180° mode of conduction for inverter. Why this inverter is called quasi - square wave inverter? [8]
b) Discuss method of harmonic reduction in inverters. Explain harmonic reduction by PWM. [8]
Unit - III
Q.5. a) Describe the working of single phase to single phase step down cyclo converter for both continuous and discontinuous conduction for a bridge type cyclo converter. [8]
b) Describe 3 - phase to 3 - phase cyclo converter with relevant circuit arrangement using 18 SCRs and 36 SCRs. [8]
OR
Q.6. a) Show that the fundamental rms value of per phase output voltage of low frequency for an m-pulse cyc1oconverter is given by Vrms = Vph (m/π ) Sin (m/π ). [8]
b) A three phase cyclo converter has output voltage of 250 V to feed a single phase load at 50 A. If the load power factor is unity, find the input power per phase and power factor. [8]
Unit-IV
Q.7. a) What is switch mode DC power supply? Discuss fly back converters. [8]
b) Explain the operation of bidirectional power supply. [8]
OR
Q.8. a) Explain the full bridge converter with various relevant waveforms and mode of operation. Compare full bridge converterwith half bridge converter. [8]
b) Discuss forward converter and obtain the necessary relation for output voltage. [8]
Unit-V
Q.9. a) Discuss multistage ac power supplies with bidirectional switches. [8]
b) Discuss current mode control and voltage mode control in ac power supplies. [8]
OR
Q.10. a) Discuss Resonant ac power Supplies. [8]
b) The load resistance ·of the resonant ac power supply is 2.5Ω. The dc input voltage is 100 V. The inverter operates at a frequency of 20 kHz with one pulse per half cycle. The turn ratio of transformer is a = 0.5 The output inverter operates with four pulse per half cycle. The width of each pulse is δ = 18°· Determine the rms load current. [8]
| Earning: ₹ 4.90/- |
