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Calculating Motor Load With A Voltmeter and Ammeter
Accurately
evaluating electric motor load can be useful when
troubleshooting conditions. In machines over 50% loaded this
can be performed with a relatively good degree of accuracy with
a True RMS voltmeter and ammeter, if more advanced instruments
are not available. If you are using an ammeter or voltmeter
with min/max capabilities, you can obtain peak loading, in
variable loads, by taking your max readings across a full cycle
of operation. Otherwise, the results are a snapshot of the
point in time and cycle of operation.
Take
voltage and current for each phase of the motor (Va-b; Va-c; Vb-c;
Aa; Ab; Ac). Calculate the average of each:

Using the
nameplate voltage (Vn) and current (An), the true load can be
estimated as:

Provided by:
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