SHAFT 0817907 - Caterpillar

When two units are paralleled there will be circulating currents. These currents are not doing useful work, but are flowing between the generators. By determining the total generator amperage and subtracting the amperage going to the load, the amount of circulating current can be determined.Circulating currents are caused by voltage differences between the two units.With cold generator sets, circulating current may be as high as 25% of rated amperes, without being considered harmful. Circulating current is part of the total generator current and this total must not exceed the amperage rating.As the generators warm, the circulating currents will decrease. The ammeter readings should decrease slightly, but the voltage meter readings should remain constant.