Importance

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Abstract

The invention relates to a method for the open-loop or closed-loop control of an asynchronous machine with or without speed feedback, the asynchronous motor being controlled by a control device (converter or servo converter). First of all, a voltage vector rotating at a rotary field frequency is specified and impressed, both the rotary field frequency and the voltage vector being determined by an open-loop or closed-loop control based on a voltage-frequency characteristic curve configured in any manner and the voltage vector being adapted by a cos φ closed-loop control. Desired values of cos φ are calculated using rating plate data and equivalent circuit diagram data for an optimum-loss or loss-optimized operation of the asynchronous machine for the calculation of cos φ_{desired value}, which results in optimized-loss operation. A value for cos φ_actual is then determined using the impressed voltage vector and a current vector or using the real power and apparent power. Thereafter, the difference is calculated between cos φ_{desired value} and cos φ_actual and a cos φ closed-loop control is fed with this input difference. A control value of the controller for cos φ is calculated and restricted and the voltage vector is adapted by the control value of the cos φ closed-loop control.

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First Claim