US 4,132,931 AGranted

Control system for a.c. motors

AssigneeHitachi, Ltd.

InventorsToshiaki Okuyama, Yuzuru Kubota, Hiroshi Nagase

Life of this patent

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Abstract

A control system for an a.c. motor having a polyphase primary winding (stator winding) and a corresponding polyphase secondary winding. The primary and the secondary windings are supplied with current from different frequency converters provided separately for each of the windings. The alternating currents flowing through the primary and the secondary windings are in opposite phase with each other. A position detector is provided for detecting the position of rotor of the a.c. motor. The magnitude of the primary current is controlled proportionally to a current reference signal in dependence on deviation of a speed feed-back signal from a speed reference signal, while the magnitude of the secondary current is controlled to a constant value. The phases of the primary and the secondary currents are controlled on the basis of the rotor position. The excitation frequencies for the primary and the secondary windings are set at a predetermined ratio between certain integers and a sum of these excitation frequencies is set to be equal to an angular frequency of rotating electrical angle of rotor.

Claims6

Dependent claims

A control system for an a.c. motor comprising:

(a) an a.c. motor having a polyphase primary winding and a polyphase secondary winding,
(b) position detector means for producing a position signal in dependence on rotor position of said a.c. motor,
(c) a first frequency converter for supplying an alternating current having a variable frequency to said primary winding,
(d) a speed control circuit for producing a current reference signal is dependence on deviation of a speed feedback signal from a speed reference signal,
(e) a current control circuit for controlling the alternating current fed to said primary winding so that said alternating current is in phase with said position signal and has a magnitude proportional to said current reference signal;
(f) a second frequency converter for supplying an alternating current having a variable frequency to said secondary winding,
(g) a second current control circuit for controlling said alternating current fed to said secondary winding so that said current is in phase with said position signal and has a magnitude of a constant value,
(h) phase sequence determining means for setting phase sequences for said primary and secondary windings in opposite phase relative to each other, and
(i) frequency control means for controlling primary and secondary excitation frequencies so that ratio between said frequencies is at a predetermined value and sum of said frequency is equal to angular frequency of rotating electrical angle of said motor.

6 more elements

Dependencies are inferred from the claim text.

Facts

Application: 05/829,000Filed 30 Aug 1977
Priority: JP 51-1048673 Sep 1976
Granted: 2 Jan 1979
Term ends: Not estimatedThe source records don’t support an estimate.

Classification6 codes

H02K 29/08
With position sensing devices: using magnetic effect devices, e.g. Hall-plates, magneto-resistors
H02K 11/33
Structural association with control circuits or drive circuits: drive circuits, e.g. power electronics
H02P 21/00
Arrangements or methods for the control of electric machines by vector control
H02P 2207/076
Doubly fed machines receiving two supplies both on the stator only wherein the power supply is fed to different sets of stator windings or to…:…