Wound field synchronous motor drive

Abstract

A hybrid synchronous motor drive circuit and method operates in one or two or more modes based on the speed of the synchronous machine. In a first mode, the synchronous machine is driven at a relatively low frequency by a current controlled voltage source inverter (VSI). In a second mode, the synchronous machine is driven at a relatively high frequency by a load commutated inverter (LCI) in tandem with the VSI. In the second mode, the LCI acts as the main power source for controlling the machine and determining machine torque and speed. The VSI acts as a harmonic compensator by compensating the dominant harmonic currents fed to the machine from the LCI such that the synchronous machine will see sinusoidal currents and thereby sinusoidal voltages at its terminals. The VSI also functions to provide sufficient reactive power at fundamental frequency so that the thyristors in the inverter are load commutated.

Dependencies are inferred from the claim text.