On-line monitoring of winding insulation health using high frequency common mode voltage from PWM

Requirements for high availability and low maintenance costs in electrical machines and drives are leading to various methods of on-line health monitoring. This paper establishes a link between standard groundwall winding insulation monitoring methods based on dissipation factor measurement and behavior of the insulation at higher frequencies. It is proposed that leakage current resulting from high frequency common mode component of PWM inverter output voltage is used for the purpose of on-line monitoring. Experimental validation of the proposed monitoring method is performed on a standard low voltage 2.83kW permanent magnet synchronous servo drive machine and conclusions are made about the viability of the monitoring system.