Low-voltage PWM inverter-fed motor insulation issues

The topic of how low-voltage insulated-gate-bipolar-transistor (IGBT)-based pulsewidth modulation (PWM) inverters create additional insulation stress through voltage reflections (due to high dV/dt) has been documented for several years. First, this paper explains and summarizes the basic causes and effects of the high dV/dt environment. Second, the methodologies of various approaches to solutions are critically reviewed. Finally, standards (such as NEMA MG1, parts 30,31) (NEMA Standards Publication MG 1, 2003) have attempted to partially address this issue. However, there are still some areas that require important clarification. This paper makes the case for what can be done to achieve the needed clarity. Testing of motor insulation systems to verify compliance with the proposed requirements is also covered.