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ECE 320: Energy Conversion and Power Electronics
Name:
Spring 2009
Homework #7 (Due: Friday, May 1, 2009)
•
Circle or box your answer (don’t forget units).
•
Staple any additional paper used to arrive at your answers to this sheet.
1.
A synchronous generator has 6 poles.
It is rated 2000 (V), 50 (kVA), with a power factor of 0.9 leading,
60 (Hz).
The magnetizing reactance,
X
m
, is 77 (
Ω
), and the ratio of the AC stator equivalent current to
the rotor DC is
I
F
/
i
f
= 5.
a.
Calculate the field current under rated conditions and draw the corresponding phasor diagram.
b.
Keeping the field the same as for part a. and lowering the power to
P
= 30 (kW), with the same
voltage of 2 (kV), calculate the reactive power,
Q
, and power factor.
Draw the corresponding
phasor diagram.
2.
A permanent magnet AC machine is connected in a Y configuration.
It has 4 poles, a field current
I
F
= 27 (A), and a magnetizing inductance,
L
m
= 20 (mH).
a.
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 Spring '09
 TimHogan

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