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UNIVERSITI TUN HUSSEIN ONN MALAYSIA

PEPERIKSAAN AKHIRSEMESTER II

SESI 2006/2007

NAMA MATAPELAJARAN : SISTEM KUASA ELEKTRIK

KOD MATAPELAJARAN : BEE 3243

KURSUS : 3 BET/BER/BEI/BEK/BTR

TARIKH PEPERIKSAAN : APRIL 2007

JANGKAMASA : 3 JAM

UNIVERSITI TUN HUSSEIN ONN MALAYSIA

FINAL EXAMINATIONSEMESTER II

SESSION 2009/2010

COURSE NAME : POWER ELECTRONICS

COURSE CODE : BEE 4113

PROGRAMME : 4 BEE

EXAMINATION DATE : APRIL 2010

DURATION : 2 ½ HOURS

INSTRUCTION : ANSWER FOUR (4) QUESTIONS ONLY

THIS EXAMINATION PAPER CONSISTS OF (8) PAGES

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Q1 (a) List the condition to turn on and off of the SCR.(4 marks)

(b) Determine the typical of the switching gate signal (pulse or continue) and the gate driven source (voltage or current) of the GTO and IGBT.

(4 marks)

(c) A power semiconductor device specifies the following switching times corresponding to the linearized characteristics shown in Figure Q1(c). From the clamped-inductive switching: tc(off) = 0.5μs. If the device operates at the switching frequency of 100 kHz, the turn-on time, ton is 1% of its switching period, current flow through the switch 8 A, on-state voltage is 1.8V and the total average power dissipation is 2 watt. Determine:

(i) the average power dissipated during on-state, Pon

(ii) the average switching power losses, Ps

(iii) the input voltage, Vd

(iv) the new switching frequency should be applied if the average power dissipated during on-state in Q1(c)(i) is reduced by 50%.

(17 marks)

Q2 (a) Figure Q2(a) is a single diode rectifier with a resistive and inductive load. The key waveforms of the circuit are shown in Figure Q2(b). There are four period processes from 0 to 2π. Explain briefly the process for each period.

(8 marks)

(b) Figure Q2(c) shows a single phase half-wave controlled rectifier has a resistive load of R = 10Ω, the voltage at the secondary transformer is 230V with ratio 2:1, and the firing angle of thyristor is 60o.

(i) Determine the expression and value of both average and rms load voltage

(ii) Determine the average and rms load current(iii) Determine average output power(iv) Determine the new firing angle, α. if the rectifier is connected to the

load which consumes 75% less than maximum possible average output voltage

(v) Draw the output voltage and current waveforms for the new firing angle α.

(17 marks)

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Q3 (a) State the advantages and disadvantages of PWM switching scheme. (4 marks)

(b) A single-phase full-bridge inverter has an RLC load connect in series with R = 10Ω, ωL = 9.89Ω and 1/ωC = 28.43Ω. The inverter frequency is 50Hz and the DC input voltage is 230V. Solve the followings:

i) express the instantaneous load current in Fourier series up to 9th order harmonic

ii) the rms load current at the fundamental frequencyiii) the THD of load currentiv) power absorbed by the load and fundamental powerv) the average DC supply currentvi) the RMS and peak supply current of each transistor

(21 marks)

Q4 (a) Define the duty cycle, D for switching frequency, fs of a DC converter.

(2 marks)

(b) Explain briefly the operation of the converter in Continuous Current Mode (CCM) and Discontinuous Current Mode (DCM).

(4 marks)

(c) Design a boost converter to provide an output of 36V from 24V source for continuous current mode. The load is 50W and the output voltage ripple must be less than 0.5%. The maximum inductor current should be 3A. The converter circuit is shown in Figure Q4(c). Assuming for the ideal components and the switching frequency is 40 kHz.

(i) Using volt-second balance technique, prove that the output voltage is

D

VV s

o

1

(ii) Specify the duty cycle of the converter(iii) Determine the capacitor size(iv) Find the average inductor current(v) Derive the expression of the minimum inductor current ILmin, during the

switch is closed(vi) Derive and determine minimum inductor Lmin, for continuous current

mode operation(19 marks)

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Q5 (a) Figure Q5(a) shows a single phase full wave ac voltage controller with resistor load. If the firing angle, α=900, plot the waveform (in one period) of:(i) Vsw

(ii) Io, and (iii) Vo

. (9 marks)

(b) Figure Q5(b) shows a single phase full-wave ac voltage controller is being employed for controlling the power flow from 220 Vrms, 50 Hz source into a load circuit consisting of a 12 Ω load resistor and a 50 mH load inductanceconnect in series.(i) Calculate the control range of the firing angle, α.(ii) Determine the maximum value of RMS load current.(iii) Determine the maximum value of output power and power factor.(iv) Derive and determine the maximum value of RMS thyristor current.

(16 marks)

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FINAL EXAMINATION

SEMESTER/SESSION : II/2009/2010 PROGRAMME : 4 BEECOURSE NAME : POWER ELECTRONICS COURSE CODE : BEE 4113

FIGURE Q1(c)

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FINAL EXAMINATION

SEMESTER/SESSION : II/2009/2010 PROGRAMME : 4 BEECOURSE NAME : POWER ELECTRONICS COURSE CODE : BEE 4113

FIGURE Q2(a)

FIGURE Q2(b)

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FINAL EXAMINATION

SEMESTER/SESSION : II/2009/2010 PROGRAMME : 4 BEECOURSE NAME : POWER ELECTRONICS COURSE CODE : BEE 4113

FIGURE Q2(c)

FIGURE Q4(c)

FIGURE Q5(a)

Ig1

Ig2

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FINAL EXAMINATION

SEMESTER/SESSION : II/2009/2010 PROGRAMME : 4 BEECOURSE NAME : POWER ELECTRONICS COURSE CODE : BEE 4113

FIGURE Q5(b)

Ig2

Ig2