GB567508A - Improvements in or relating to electric motor controllers - Google Patents

Abstract

567,508. Control of D.C. motors. IGRANIC ELECTRIC CO., Ltd. July 1, 1943, No. 10685. Convention date, July 16, 1942. [Class 38 (iii)] Control apparatus for a hoist motor MI, particularly one supplied by a Diesel-driven generator, comprises (1) a master controller MS having means selectively to establish power connections for hoisting, or power and dynamic braking connections for lowering, and to afford speed control ; and (2) regulating means to render substantially uniform under heavy and light loads a high lowering speed selectable by the master controller and to interrupt the power connections at certain lowering speeds when the motor is being overhauled by the load and tending to return current to the generator. The regulating means comprises a reverse-current relay ICR which carries the armature current of the motor when the controller MS is in the lowering positions and which drops out to de-energize the operating.coil of a line switch 1KO when the armature current reverses due to overhauling. When the relay is closed and the controller moved to its final lowering position 5, an electromagnetic switch IA, which is closed in all the other positions of the controller, is energized and opens a short-circuit on a section R1 of field resistance to provide a high lowering speed for an empty hook or light load. The system shown embodies the features described in Specification 557,582, and, with switches H, M closed, provides for the series connection of the armature A, field F, brake winding B and resistors R2-R6 in the hoisting positions of the controller, the resistors being cut out sequentially by switches 2A-6A, preferably subject to time control, as the controller is moved through positions 1-5. Switch 2DB is closed only when the controller is in the off position, thus establishing a dynamic braking loop which excludes resistances Rl-R4 and brake coil B, switches 5A, 6A then being under the control of a relay VR for graduation of the braking effect as the motor comes to rest. Current may be diverted from the armature by closure of switch 1KO in the first and second hoisting positions to provide for slow speed hoisting. Movement of the controller to the lowering positions closes switches 1KO and IDB and opens H, thus connecting the armature and field in parallel, the field circuit including the resistors R4-Rl which are sequentially inserted with progressive movement of the controller, R1 being subject to the over-riding control of relay ICR.