Over the last few years, several medium-voltage, pulse-width modulated, voltage source inverter drives have been introduced to the market. These drives are based on different power stack topologies and different power devices. This article reviews various MV PWM VSI power stack topologies in the power range 2-7MW. It also examines and compares a number of different high-power IGBT-based, converter stack designs suitable for 4.6k AC RMS output voltage.