The volt-per-Hertz (V/F) drives of induction motors
(IMs) are widely used in industrial applications because these
drives are simple and cost effective. V/F drives operation is based
on speed command and unable to toque control. In industrial
applications the IMs are coupled to feed heavy loads. Coupling
the IMs in addition to economic advantage leads to reduction of
energy consumption. When the load becomes heavier the number
of IMs that feed the load will be increased and vice versa.
However with coupled IMs, the load is not shared properly and
some of the IMs may be overloaded. For a proportional load
sharing using of the torque control drives seems to be necessary,
but these drives are complicated and expensive.