Cutler-Hammer - Eaton Canada
Cutler-Hammer - Eaton Canada
Cutler-Hammer - Eaton Canada
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Input Line Considerations<br />
The value of source impedance is expressed as<br />
a percent of the effective impedance of the<br />
drive.<br />
To determine the source impedance as a<br />
percent of the effective impedance of the drive,<br />
you must know:<br />
¥ The short circuit capacity of the power<br />
source at the driveÕs input power terminals.<br />
¥ The full load (output) current rating of the<br />
drive (found on the nameplate).<br />
The following calculation provides the source<br />
impedance as a percent of the effective<br />
impedance of the drive:<br />
Full Load Current<br />
Short Circuit Capacity<br />
* 100<br />
= Source<br />
Impedance<br />
Pre-Installation<br />
INSTALLATION<br />
The short circuit capacity must be at least 20<br />
times the full load current rating (5%<br />
impedance) and no more than 100 times the full<br />
load current rating (1% impedance).<br />
For example, if the full load (output) current of<br />
an AF93/IS903 drive is 22 amps and the short<br />
circuit current capacity of the power source is<br />
2200 amps, the source impedance is:<br />
22<br />
2200<br />
* = 1.00%<br />
100<br />
Since the design of a power distribution system<br />
often includes a short circuit capacity study,<br />
power distribution system drawings or other<br />
distribution system documentation may show<br />
the short circuit capacity at various points. If this<br />
data is not available, contact your <strong>Cutler</strong>-<br />
<strong>Hammer</strong> sales representative or distributor for<br />
help on estimating or calculating short circuit<br />
current capacity.<br />
AF93/IS903 Instruction Manual<br />
2-9
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