Start-Up Torque Limitation of Induction Motors by Asymmetrical Starting Connections

ABSTRACT Smooth acceleration during the start-up is important in some industrial applications of induction motors. An example is given by texile machines, where the breaking fibre threas during the start-up must be avoided. An asymmetrical starting scheme, implemented by means of an external resistance inserted in one of the motor phases, can provide a simple, but elective, solution to this problem; the value of the resistance Mill depend on the assigned value of the maximum torque developed. To compute the transient behavior during the start-up, a dynamical motor model, effective also of describe asymmetrically connected machines has been used to study the torque control problem. The present paper reports the results obtained with reference to a 70 W induction motor supplied by a frequency converter. A comparison between experimental data and simulation is presented.