Disturbance free operation of a multiphase current regulated motor drive with an opened phase

An improved induction motor control strategy is proposed incorporating a multiphase machine which allows for continuous, disturbance free operation of the drive even with complete loss of one (or more) legs of the inverter or motor phase. A complete analysis of both even phase and odd phase machines utilizing this control and circuit concept is presented. By using a five-phase or a seven-phase machine, it is possible to take advantage of the additional degrees of freedom as a result of more phases. It is shown that when one phase is open circuited, with appropriate control, the zero sequence current is no longer a necessary component as in a three-phase machine. That is, one can eliminate the need for a neutral line and the machine can still be controlled so as to produce a smooth nonpulsating torque. It has also been determined that the ratings of motor and inverter will both benefit by the use of extra phases.>