Scalar control systems for a traction induction motor

A brief review and comparative characteristics of scalar control systems for traction induction motors for using in the traction electric drive are presented. It is shown that, despite the obvious advantages of the systems of vector control and direct torque control, scalar control systems have found wide application. The operation features of scalar control systems with stability0 of absolute slip and a minimum of stator current are considered. Based on the equivalent circuit of an induction motor taking into account the stator and rotor iron loss, a comparative evaluation of the considered scalar control systems based on the criterion of the efficiency coefficient taking into account the temperature of the stator and rotor windings is presented. Simulation results in the MATLAB environment for an 11-kW induction motor are presented. It is established that scalar control systems operating under the principle of a stator current minimum have an advantage, as this maintains the desired torque value with higher values of efficiency coefficient, which decreases electromagnetic loads and power loss. It is shown that it is necessary to take into account the influence of windings temperature on the stator voltage and the parameters of the control system in connection with its affect on the minimum stator current and optimal absolute slip ensuring extremal control by current minimum.