Catalogue AVX Medium Power Film Capacitors
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Medium Power Film capacitors
Application Notes
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Lower power will give similar results, and for power up to 10 kwatts, capacitance value becomes so small that film technology still constitutes the best solution.
Even at 100Hz rectifier frequency, no more than 555uF are needed, supply voltage and ripple still the same than previously.
0.5
To illustrate, we will take a concrete example:
DC voltage 1000 Volts U ripple 200 volts
100
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80
60
0.4
g
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40
CP
o
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ca O
20
0.2
0
0
400
800 1200 Frequency (Hz)
1600
2000
0.1
0
P
Irms
1 MW
2468 Arms
500 kW
1234 Arms
100 kW
247 Arms
100 150 200 250 300 Frequency (Hz)
350
400
2) OVERVOLTAGE DESIGN
We will consider light traction application, like metro, tramway, electric buses, ...
DC link voltage wave form:
It becomes necessary to have a zoom on low frequency:
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co +j
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.
co O
40
20 h
DC Link Filter ^-■ ■ ■—■ ■ ■
m
0 100
3D
150 200 250 300 Frequency (Hz)
350 400
MOTOR
To compare with electrolytic solution, we will take a current capability of 20mA per uF for electrolytic capacitors. First case, power at IMwatt:
Rms. current is 2468 Arms, which would impose minimum capacitance value of 123.4mF (taken in account 0.2Arms. per uF).
If we look at this value on the curve, we can see that this capacitance value is needed (the given example for film technology) for a rectifier frequency lower than 100Hz.
So, with 3 phases, 6 diodes rectifier, frequency will be 300Hz.
We can see on 1 megawatt curve that capacitance needed is 18.5mF. Film solution will be almost 4 times smaller than electrolytic solution, with high reliability in addition.
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page 53 p.53
page 54 p.54
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page 60 p.60
page 61 p.61
page 62 p.62
page 63 p.63
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pdf-page pdf di En 2009-01-02-07