Reconfiguration of Multilevel Inverters and Their Impact on Insulation Breakdown Time

Reconfiguration of multilevel inverters (MLIs) has been widely used in motor drives to improve their reliability, make them fault tolerant and reduce the downtime. However, PWM-like inverter output has a large
$dV/dt$
and stresses the insulation systems in motor drives, thus leading to premature insulation failure. Reconfiguration of MLIs changes the number of voltage levels and
$dV/dt$
of the inverter output and subjects the insulation systems to a combination of different
$dV/dt$
during its operation. This effect on motor insulation is not yet fully known. Thus, it is important to understand the effect of reconfiguration of MLI, or the general impact of the MLI's number of levels, on insulation breakdown time. In this paper, magnet wire enamel insulation is stressed by an active neutral point clamped inverter (ANPC) that is reconfigurable for 3-, 5-, and 7-level outputs. The breakdown time of magnet wire enamel insulation is reported. This paper shows the experimental capability, details of the insulation material, methodology of testing and insulation breakdown time under different multilevel inverter configurations.