An improved V/F control scheme for symmetric load sharing of multi-machine induction motor drives

The traditional low-cost Volts-per-Hertz (V/F) induction motor (IM) drives typically operate based on speed command, whereas the developed torque is consequently determined according to the torque-speed characteristics of the machine. In multi-machine load-sharing applications, it is preferred to have number of identical IMs; whereas in practice, deviations among motor parameters is probable and will result in disproportionate sharing of the mechanical load and even overloading one or several machines. In this paper, an improved V/F scheme is presented, which compensates for possible variations in the motor parameter (e.g. rotor resistance) and balances the load accordingly. The new method is shown to be effective and easy to implement, and may be readily extended to an arbitrary number of motors driving a common load.