Dictionary of Electrical Engineering

Commonly used terms in the Electrical industry.

a condition of operating a synchronous machine, in which the current to the DC field winding is insufficient to establish the required magnetic flux in the air-gap. As a result, the machine requires reactive power from the AC system. An underexcited synchronous motor operates at a lagging power factor, as it appears as an inductive load to the AC system. An under-excited synchronous generator operates with a leading power factor, since it must deliver power to a leading (capacitive) system.