Strategies for magnetizing speed‐sensorless induction machines

Abstract

Whenever possible, only easily measurable quantities like stator currents and DC link voltage are used to control inverter‐fed induction motors nowadays. Also for high‐performance AC drives speed‐sensorless control of induction motors has received increasing attention from the viewpoint of cost, trouble immunity and reliability. Different algorithms for speed identification are known. They allow good performance of torque or speed control in almost the whole operating area of an induction machine without using rotational transducers. One remaining problem is to start the machine when mechanical speed is not known. This paper now presents two new strategies for magnetizing a demagnetized speed‐sensorless induction machine also with non‐zero speed.

Magnetization of speed sensorless squirrel-cage induction generator for wind power application using a phase-locked loop

“…Hence, in order to achieve a successful magnetization using voltage-based flux estimation methods, these methods have to be modified. It is interesting to note that, although this subject matter is very attractive, little has been published about it [20][21][22]. The methods proposed in [20][21][22] require transient excitation of the machine or injection of the DC stator current component to identify the necessary speed without using a speed sensor.…”

“…It is interesting to note that, although this subject matter is very attractive, little has been published about it [20][21][22]. The methods proposed in [20][21][22] require transient excitation of the machine or injection of the DC stator current component to identify the necessary speed without using a speed sensor. However, commercially available speed sensorless drives contain a flying start function and are thus able to determine the rotor speed of a non-magnetized induction machine during the start-up.…”