One of the negative aspects of the newer devices is that the low switching loss is typically accompanied by a very short transition time. This short transition between on and off states implies a high dV/dt output of the inverter. The high dV/dt results in capacitively coupled current flow according to Equation 4.
In addition to the capacitively coupled current, the high dV/dt also results in a higher peak voltage (ringup) due to cable-to-load mismatch. Finally, the high dV/dt also results in an instantaneous high voltage across the first windings within the ac motor. A companion paper, “AC Induction Motor Insulation Issues in High dV/dt Environments,” addresses this in greater detail.
AC induction motors are likely to continue to be increasing sources of variable speed rotating power. Their successful use in variable speed applications is a function of the collective understanding of the various parties involved in the specification, design, application, and integration of the system.