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Power Factor Testing

Lagging Power Factor Testing (Adding Inductive Load)

​By adding an inductive load to the resistive load, lagging power factor can be obtained. Commercial loads, as well as generator sets, are rated at the nominal power factor of 0.8 lagging. This number is the cosine of the angle made between the KW and the KVA in the diagram below:

The magnitude of inductive load required to obtain 0.8 power factor is 0.75 X the KW (1000kw + 750kvar = 1250kva at 0.8 lagging power factor). As a point of interest, 0.75 is the tangent of the aforementioned angle. Keep in mind when sizing cables that the full load current at the rated KVA must be calculated.

Leading Power Factor Testing (Adding Capacitive Load)

The same rationale as Low Power Factor Testing applies to leading power factor, except capacitive load is added. Leading power factor testing is rare and specialized. Most engine generator sets cannot tolerate more than a very small degree of leading power factor.