Direct measurement of power angle of synchronous machines

Abstract

In this paper, a novel method of measuring load angle of synchronous machines is presented. The load angle of the synchronous machine is directly related to the emf induced in the auxiliary winding of a load angle meter that is attached to the shaft of the main machine. The meter consists of a round rotor half and a salient pole half, which are coupled together and suitably interconnected. When the axis of the rotating stator excitation mmf coincides with the d-axis of the salient pole half of the device, the output voltage from its auxiliary winding will be zero and when it coincides with the q-axis, the induced emf will be a maximum. In general, the emf is proportional to the sine of the load angle.