DTC IM drive losses — Simulation and measurements

Pulse-width modulation (PWM) inverters are widely used to control electrical machines accurately for process needs, thereby increasing the system energy efficiency. The PWM methods, however, have also adverse effects and produce additional losses in the motor compared with the sinusoidal supply. Naturally, additional losses increase the motor temperature and, at least in principle, result in derating of the machine in converter use. A reliable and reasonably accurate loss model of an induction motor drive system is important for the performance prediction of a variable-speed drive. A frequency converter circuit model that includes an input choke, a diode rectifier, an intermediate DC circuit, and an IGBT inverter module is coupled to a FEM motor model. The drive model is controlled by closed-loop direct torque control (DTC). The frequency converter losses are calculated with analytical equations in a circuit model, and the FEM motor model provides the motor losses. The simulation results are compared with the measurement results.