Method of Limiting Shaft Voltages in AC Electric Machines

Abstract

The article presents a new method of counteracting shaft voltages and currents in AC electrical machines. It is based on the use of an auxiliary winding located in the stator of the machine. The design of a test stand adapted to the measurement of shaft voltages of the machine, based on the prototype of a synchronous machine with permanent magnets, has been presented. The model was used to conduct a number of laboratory tests aimed at confirming the functionality of the auxiliary winding in various operating states of the machine (including no-load and load condition during generator operation). The article focuses on demonstrating the beneficial effect of the auxiliary winding on the level of induced shaft voltages in an electric machine. In order to confirm the close dependence of the circular flux in the stator yoke on the shaft voltage, shaft voltage measurement results for various cases of external power supply of auxiliary winding forcing a circular flux are presented. Regardless of the laboratory tests, a simulation model of a synchronous machine with permanent magnets, on which calculations were carried out to analyze the work of the auxiliary winding located in the stator yoke, was developed. The article is supplemented by a review of damage to electrical machines with a detailed description of bearing defects, as well as a brief de-scription of issues related to the mechanism of generating shaft voltages and currents in electrical machines and methods of counteracting them.

Keywords

• bearing currents
• shaft voltages
• electrical machine
• bearings