Patent GB-714735-A (GB)
Title: Improvements in control systems for electric multi-motor drives
IPC: H02P5/74
Filed: 1952-04-15
Abstract: 714,735. Control of motors. IGRANIC ELECTRIC CO., Ltd. April 15, 1952 [April 18, 1951], No. 9407/52. Class 38(3) A load is driven at high speed directly by a large motor LM and at low speed by a small motor SM through reduction gearing and an electromagnetic clutch energized by coil C1. Means are provided whereby, when stopping in the event of the load being driven by the large motor, a relatively high braking torque is applied, and, when stopping with the load driven by the small motor, a relatively low braking torque is afforded. Before operation can be commenced, a switch 17 must be opened and a reset switch temporarily closed to start an alarm 21 and to energize stop relay 14a. The clutch coil C1 is then connected in circuit with resistors r5, r6, so that both the clutch and a brake coil B1  for the small motor are energized at low voltage. Inching is effected by temporary acuation of a button 11, the reset button 15 being first momentarily closed. Operation of the inch button starts the motor SM, de-energizes the brake coil B1 completely, applies full voltage to the clutch coil Cl, and stops the alarm 21. When the inch button is released, the motor SM is disconnected, the brake coil B1 and clutch coil C1 both being energized at low voltage. Reclosure of the button 15 is necessary prior to another inching operation. For continuous operation, a button 12 is momentarily depressed to start the small motor SM and a pilot motor 5 which drives crosshead 4, the clutch coil C1 having resistor r5 in circuit therewith. The brake B is fully removed and the small motor drives the load at low speed. The small motor may be stopped before the load is transferred to the large motor by depressing button. 14 to open contacts S and to engage brake B at low torque. The pilot motor 5 is reversed to return the crosshead to the " off " position. When the crosshead in its upward movement during the running of the small motor reaches position 4, the clutch Cl is de-energized to uncouple the motor SM from the load and contacts L are closed to energize the motor LM. Depression of the button 12 moves the crosshead to its fifth position whereupon the motor SM is disconnected and is braked at low torque. To decelerate the drive when the load is being driven by the large motor, a button 13 may be actuated to return the crosshead to position 4 so that the small motor is started and relay 30 is connected to tachometer generator TG. Continued actuation of the button 13 causes the crosshead to move to position 3 in which the large motor is disconnected but relay 30 prevents engagement of the clutch until the large motor reaches approximately zero speed. For complete stoppage, button 14 is actuated to disconnect the small motor and apply brake B at low torque. When the button 14 is actuated with the drive operating under the large motor, relay 30 is energized so that brake contacts BR for the large motor are closed. The brake coil B1 is energized at full voltage whilst low voltage is applied to the clutch coil C1 so that both motors are braked at full torque but are coupled at low coupling- torque. The brake for the large motor has a tendency to reverse rotation when zero speed is reached during deceleration, the brake for the small motor, together with the clutch, prevent reversal of the motors, however. A relay SR prevents coupling of the motors during deceleration unless the brake B develops full braking torque. Specifications 539,203, 567,885 and 583,820 are referred to.