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CONCORDIA UNIVERSITYDEPARTMENT OF ELETRICAL AND COMPUTER ENGINEERING

ELEC 433/6461 – Power Electronics/Power Electronics IAssignment #1: Review of basic concepts and definitions

Due date: September 28 2015 in the mailbox of Dr. Lopes (EV5.175).

1) A 60 Hz three-phase induction motor draws 25kVA at 0.8 lagging power factor from a 220-V LL

source. It is desired to improve the power factor to 0.92 by connecting a capacitor bank in parallel

with the motor. A) Specify the required kVA (kVAr) rating of the capacitor bank. B) If the

capacitor bank is ∆ -connected, find the value of the capacitors. C) Determine the line current

before and after the addition of the capacitor bank. D) For a per-phase equivalent circuit, show

the phasor diagram of the load current, capacitor current, source current and source voltage

(reference phasor).

2) A single-phase full-bridge diode rectifier was simulated with PSpice and the following results

were obtained: 1) Waveforms of the ac side current, ac side voltage and dc side voltage; 2)

Harmonic spectrum of the ac side current. Assuming that φ1 = 10 °, compute: a) The total rms

value of the ac side current; b) The THD of the ac side current; c) The crest factor of the ac side

current; d) The active, reactive and apparent power absorbed by the converter; e) The power

factor and the displacement power factor of the converter.

Time

100ms 105ms 110ms 115ms 120ms 125ms 130ms 135ms 140ms 145ms 150msV(Rload :1 ) - V(Rload :2 ) V(Vs :+)

-200V

0V

200VI(Ls)

-40A

0A

40A

SEL>>

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Frequency

0Hz 0.1KHz 0.2KHz 0.3KHz 0.4KHz 0.5KHz 0.6KHz 0.7KHz 0.8KHz 0.9KHz 1.0KHzI(Ls)

0A

4A

8A

12A

16A

(900.000,439.489m)

(780.000,468.070m)(660.000,922.143m)

(540.000,1.0312)

(420.000,2.2032)

(300.000,6.4795)

(180.000,11.734)

(60.000,15.348)