The performance of speed-controlled induction motor drives, without a direct sensing of the flux, depends heavily on the accuracy with which the motor parameters are known. They change widely with the temperature, frequency, and current amplitude. With a control based on rotor position measurement and inner current control loops, the rotor resistance is the most essential changing parameter. A method of automatic adaption of the control to the changes in this parameter is presented. The proposed strategy is based on the measurement of only motor voltages and currents and is implemented by analog means. It does not make use of transducers or probes to measure the temperature or the flux in the motor.

Parameter Adaption for the Speed-Controlled Static AC Drive with a Squirrel-Cage Induction Motor

Field orientation has emerged as a powerful tool for controlling ac machines such as inverter-supplied induction motors. The dynamic performance of such a drive is comparable to that of a converterfed four quadrant dc drive. The complex functions required by filed-oriented control may be executed by microprocessors on line, thus greatly reducing the necessary control hardware. It is shown that the flux signals may be derived from sensing coils or, with some compromise in performance, from the stator voltages and currents. The speed signal is obtained from a digital tachometer. Results from a 2-kW experimental drive are given.

Field-Oriented Control of a Standard AC Motor Using Microprocessors

A family of schemes for the control of torque and speed of the induction machine is described. It has been developed with the intention of closing the gap between high dynamic performance drives, requiring measurement of the rotor position or the field, and the simpler schemes with poor dynamic performance. Dynamic behavior and a static accuracy have been achieved which promise a broad range of applications. This is due also to the relative simplicity of the equipment and insensitivity to changes in resistance parameters. Implementation with a voltage source inverter and a current source inverter are shown.

Control Methods for Good Dynamic Performance Induction Motor Drives Based on Current and Voltage as Measured Quantities

The induction motor is well known as the workhorse of industry. The development of variable speed induction motor drives has a long history of more than four decades. Today's sophisticated industrial drives are the result of the extensive research and development during the last decades. In this paper the historical and recent developments and major milestones in control of induction motors are pointed out first and second how research results were translated into today's industrial standards, and third at last, what are the current trends in research and industry are summarized.

State of the Art of Induction Motor Control

A simple control system for induction motor drives with the current source inverter is presented. This system is based on the idea of field-orientated control. In contrast to well-known ways of realization a torque proportional quantity is calculated from stator voltage and current without explicit flux calculation or integration. A speed sensor is not required. The theoretical principles of this method are discussed. Some transients which illustrate the performance of some different system variants are presented.

Felix Elaschke

Papers

Verfahren der Felderfassung bei der Regelung stromrichtergespeister Asynchronmaschinen