Neutral-point clamped three-level general purpose inverter - features, benefits and applications

This paper introduces a neutral-point clamped three-level PWM inverter for general industry applications in the 400-480 volt range. Since the voltage stress applied to the power devices of three-level configuration is half that of the two-level version, this topology was traditionally used for medium voltage drives both in industrial and traction areas. Basic behavior of the NPC topology brings significant advantages to the low voltage applications as well. Especially, the lower voltage steps associated with the switching help in the mitigation of problems related to surge voltages at the motor terminals, leakage current, shaft voltage and bearing current, and so on. The three-level NPC inverter newly introduced for general-purpose application combines sophisticated PWM technique and modern control laws to yield high performance drive. The features and benefits of this product are presented along with measured waveforms.