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US 4,543,520 AGranted
Induction motor slip control
AssigneeKollmorgen Technologies Corporation
InventorsGeorge E. Danz, C. Calvin Shuler
Life of this patent
Estimating the term…
Abstract
A variable frequency AC induction motor servo control system wherein slip is generated as a function of stator current. In a preferred embodiment the slip per ampere ratio is constant in the range from zero to approximately base speed and thereafter increases exponentially as the rotor speed increases above base speed.
Claims2
A servo control system for an AC induction motor comprising:
- a servo loop responsive to the speed of the AC induction motor and a desired speed indication to provide an error signal proportional to the difference between said speed indications;
- means providing a speed pulse train having a repetition rate proportional to the speed of the AC induction motor;
- a slip pulse generator for providing a slip pulse train, said slip pulse generator being
- responsive to an indication of motor excitation current, and
- to motor speed, so that
- the repetition rate of said slip pulse train is a function of both motor current and motor speed;
- means providing a digital rotating vector indication in accordance with the summation of said speed pulse train and said slip pulse train;
- and
- conversion means for providing a synthesized sine wave excitation for the AC induction motor
- in accordance with the phase and frequency of said vector indication, and
- with an amplitude proportional to said error signal.
8 more elements
Dependencies are inferred from the claim text.