Patent GB-397004-A (GB)
Title: Improvements in or relating to controllers for electric motors
IPC: B66B1/08
Filed: 1932-12-28
Abstract: 397,004. Master control of A.C. motors. IGRANIC ELECTRIC CO., Ltd., 147, Victoria Street, London.-(Assignees of Kuhn, C. W.; N. 12th Street, Milwaukee, Wisconsin, and Ryan, P.; 430, Southern Boulevard, New York, both in U.S.A.) Dec. 28, 1932, No. 36662. Convention date, Jan. 2. [Class 38 (iii).] A motor control system includes a plurality of electro-responsive accelerating switches 5, 6, 7 with restraining windings 5b, 6b, 7b which, on starting the motor, are connected in series in a circuit not including the motor across a direct-current supply L11, L12, means being provided for controlling shunt circuits for said windings to render the switches responsive in a given sequence, the response being subject, in certain instances, to a delay which is a function of the self inductance of the respective restraining windings. The invention is shown as applied to a three-phase motor M for driving an elevator. The motor has low and high speed primary windings P1, P2 and a squirrel-cage rotor S, the connections between the windings and the lines L1, L2, L3 being controlled by a main switch 1, up and down reversing switches 2, 3, a slow-fast switch 4, up and down relays 15, 16 and relays 17, 18, 19 for controlling the rate of acceleration and deceleration of the motor. Movement of a master controller MS from the off position shown into the first position in either direction effects response of the main switch 1 and one of the switches 2, 3, thereby connecting the low speed winding P1 to the lines through resistances R1, R2 and simultaneously energizing a winding B1 to release a brake B on the motor. One of the relays 15 or 16 responds at the same time as the corresponding switch 2 or 3, and connects the operating windings 5a, 60, of the resistance switches 5, 6 in parallel and the restraining windings 5b, 6b, 7b of all three resistance switches in series across the lines L11, L12. The winding 5b is short-circuited by contacts on the relay 17, so that the switch 5 responds immediately to cut out the resistance R<1>. Response of the switch 5 short-circuits the winding 6b and switch 6 responds to cut out the resistance R2 after an interval determined by the self inductance of the winding 6b. On moving the controller MS into its second position, the slow-fast switch 4 responds to interrupt the connections for the winding P1 and to complete those for the winding P2. Relay 17 responds at the same time and shortcircuits the restraining winding 7b, whereupon the switch 7 responds, after an interval determined by the inductance of the winding 7b, to cut out the resistance R3. Movement of the controller MS from either of its second speed positions breaks the energizing circuits for the switches 4, 7 and relay 17, and the connections to the winding P2 are interrupted and those to the winding P1 re-established for braking the motor. The dropping out of relay 17 re-establishes the energizing circuits of the switches 5, 6 and the resistances R1, R2 are successively cut out, to increase the braking effect on the motor, after intervals dependent on the self inductance of the restraining windings. The system includes door switches 26, all of which must be in closed position, before the motor can be started. Up and down limit switches 20, 21 and overtravel switches 24, 25 are also provided for stopping the motor in certain positions, and slow-down limit switches 22, 23 for de-energizing the switch 4 and relay 17 to effect braking of the motor when the elevator is approaching the limiting positions. Specification 232,807, [Class 38 (iii), Electric motor control systems &c.], is referred to.