Efficiency consideration of DC link soft-switching inverters for motor drive applications

This paper critically evaluates efficiencies of DC link soft-switching inverters suitable for motor drive applications. Three types of DC link soft-switching inverters, including actively clamped resonant DC link inverter, clamped-mode resonant pole-inverter, and auxiliary switch commutated resonant pole inverter, were studied. Loss separation methods for evaluating soft-switching inverters were developed using a simplified device model. The developed methods were applied to a 50 kW induction motor and its associated inverters for efficiency evaluation under different speed and torque conditions. The evaluation results were then compared with those of the hard-switching pulse-width-modulation (PWM) inverter. The clamped-mode soft-switching inverter, although saving the switching losses, shows poorest efficiency because its resonant circuit associated circulation losses are very substantial. The actively clamped resonant DC link and auxiliary switch commutated inverters show the same level of substantial efficiency improvement over the hard switching PWM inverter. The actual energy saving, however, can be further improved by optimization of circuit components and selection of the inverter switching algorithm in actual implementations