GB922843A - Control equipment for induction motors - Google Patents

Abstract

922,843. Control of A.C. motors. F. DE'DIFNICO. April 3, 1959 [April 3, 1958], No. 11442/59. Drawings to Specification. Class 38 (3). [Also in Group XXXV] Relates to the control of reversible induction motors whose rotor resistance is such that the torque increases continuously over a range from zero slip to 200% slip. Means are provided to afford an alternating stator flux which is gradually changeable to a rotating flux in either direction. A single-phase motor has two poles displaced through 90 degrees, and each pole-winding is in series with a phase-displacing impedance which may be gradually changed from being wholly capacitive to wholly inductive. A two-phase motor has one of its polewindings associated with phase-shift regulators, which may be auto-transformers, and a three-phase motor has such regulators associated with two of its pole-windings. In another arrangement, a pole is angularly displaceable around the rotor axis, the rotor being divided into two portions which are mechanically coupled and each associated with a single pole. A three-phase motor has its rotor divided into three parts, each associated with a pole, two of the poles being angularly displaceable. Each pole may have an auxiliary winding which is short-circuited, or associated with series impedance for speed regulation. In a further embodiment, the motor has a regulator with three pairs of windings, the windings of each pair being series-connected and one situated on a stator and the other on a rotor. In one position of the rotor the regulator windings are aligned to provide maximum flux linkage and maximum inductance, the motor then being stationary. Adjustment of the rotor of the regulator in either direction causes the motor to run in one direction or the other. Another regulator comprises two reactors connected to the motor windings through sliding contacts. Alternatively, the reactors may be saturable.