Efficiency optimization techniques via constant optimal slip control of induction motor drives

The paper proposes a novel control technique that is able to optimize the efficiency in scalar controlled induction motor drives. The proposed strategy is based on a constant-optimal slip control and is able to modify the magnetizing flux value increasing the efficiency at light loads. Differently from the optimization methods present in the literature, the proposed approach does not require the model of the machine, does not solve any losses minimization equation and is not based on a minimum losses or minimum power search algorithm. The presented technique is based on an intuitive adaptation of the well known maximum torque per ampere (MTA) algorithm to a new version for scalar control, ensuring a constant-optimal slip. A key point is the possibility to achieve the efficiency optimization by using the same hardware as in standard adjustable speed drives operated by V/f or conventional slip control. An experimental evaluation has been accomplished on a 1,5 Hp induction motor drive to measure the losses minimization and verify the dynamic performance of the proposed method