The analysis of saturation effects on transient behavior of induction machine direct starting

This study deals with the transient behavior of induction machines starting directly from the power distribution network and proposes a model to predict the starting current and torque. Direct starting may cause important faults on both power network and load. Torque oscillations during transient may resonate with mechanical load system. The first peak value of torque is also critical for machine loads. On the other hand, during direct starting, high transient currents make large voltage drops on power system resulting in failing other connected loads. Therefore an accurate transient machine model becomes imperative in order to estimate starting torque and starting current for the overall system design. The prediction of induction machine transient performance requires proper account of the saturation effects. In the proposed model, the main flux path and the leakage flux path saturations are separately considered. They are modeled by functions of corresponding currents for both stator and rotor sides. As reliable experimental data on high power induction machines are not easily available, experimental measurements have been carried out on a 3 phase, 45 kW, 4 poles delta-connected induction motor. Finally, experimental and simulation results are compared to prove the performance of the proposed model.