Recently, interior permanent magnet synchronous motors have been investigated for traction applications because of their advantages. Simultaneously, efforts to reduce the losses of the motors have also been performed. This is a complex task because it is difficult to determine exactly motor parameters and, furthermore, the motor parameters can be changed due to the magnetic saturation. This paper presents a new approach to minimize the electrical losses of the interior permanent magnet synchronous motors. Two control strategies based on unsaturated and saturated motor model are analyzed. To overcome the problem of parameters unavailable, a procedure is proposed to estimate parameters of the loss minimization conditions. Therefore, the knowledge of the exact motor model is not required. The simulation results show improved performances.