Insulation Health State Monitoring of Traction Machines Based on Online Switching Transient Exploitation

Abstract:
In modern inverter-fed drive applications on-line monitoring systems offer the advantage of maintenance cost reduction and reliability increase. High switching frequencies combined with high inverter output voltage dv/dt rates increase the stress on the insulation system of the fed motor and lead to insulation deterioration. The proposed insulation monitoring method is able to detect imminent stator insulation defects by evaluating the current response induced by inverter switching. Due to effects occurring during the aging of the insulation, e.g. changes of electrical parasitic components like winding capacitances, deviations in the high frequency behavior of the current response are monitored for insulation status detection. No additional sensors are necessary beside the current transducers already applied for the control of the machine. The paper presents experimental results of a 1.4 MW induction machine designed as traction motor for railway applications, fed by a dv/dt testing inverter prototype equipped with SiC-MOSFET semiconductors.