A modulation technique is described in which a controller modulates the output AC voltages to introduce an offset to the phase that is most positive or most negative such that the phase is clamped to the +dc supply when the respective phase is most positive and to the −dc supply rail when most negative. The offset is provided by introducing a common mode component voltage to all of the phases over a plurality of output angle segments. In order to reduce the Noise Vibration and Harshness (NVH) and EMI, the common mode component voltage amplitude is varied over the output angles within the respective segment between a minimum and a maximum in order to control a slew rate of the rising or falling edges of the three phase AC output voltages.