Partial discharge measurements in PWM inverter-driven low-voltage motors

Partial discharge (PD) on low-voltage motors was not recognised as a potential issue until recently. Evolving converter technology has challenged the limit of LV insulation systems. Possible reliability issues have been recognised due to PDs, especially for inter-turn insulation. PD is related to the extension of standard 415 V insulation systems to PWM inverter fed applications on 415 V and 690 V systems. The problem is exacerbated in inverter systems without dv/dt filters and run through long cables. This paper investigates the possibility of measuring PDs for such applications and aims to develop a practical insulation assessment methodology based on the IEC-TS 60034-18-41 proposal.