This paper describes the principles of optimization of asynchronous variable frequency induction motor drives with scalar open loop control systems. The development problems of special control laws designed for dynamic (startingbreaking) modes are discussed. Concept of integral electromagnetic conversion efficiency criterion is introduced. From the standpoint of the above criteria, the efficiency of the following control laws is considered: the control law obtained from static equations of the induction motor; the control law obtained from dynamic equations and the control law with initial magnetization of the motor by low frequency voltage. Reasonable areas of application of these laws are defined. The using of the initial magnetization allows to significantly reducing initial inrush stator at the beginning of start process. This allows to further reduce losses in the motor and to improve the ratio of «current torque» at start. The additional losses caused by the premagnetization are much smaller losses caused by the inrush current during start up in traditional systems. Simulating results are given.