Application of dead time compensation to variable speed drives

The performance of a variable speed drive system is analysed in terms of its output torque characteristics. As a consequence of introducing dead times, the output voltage applied to the motor load has a reduced fundamental voltage component and added unwanted low order voltage harmonics. The effect of reducing the fundamental voltage causes both a step change in torque over a gear change and a reduction of the steady state output torque. Compensating for dead time results in a negligible torque perturbation when gear changing and an increased steady state torque, although this torque is still less than the ideal at low frequency due to the effect of the motor´s stator resistance