GB275702A - Electric motor control - Google Patents

Abstract

275,702. British-American Laundry Machinery Co., Ltd., (American Laundry Machinery Co.). April 30, 1926. Systems for alternating-current motors only; electric braking; safety arrangements. - The starting and braking-circuits of a number of motors running..on a common three-phase A.C. supply are so controlled that no motor may be started or braked whilst any other is being started or braked. The braking is effected by reversing the stator connections. Relays 17, 18, one in the stator circuit of each motor 4<1>, 4", control relays 19, 20, one for each motor. Each relay controls contacts a, b respectively in the circuits of contactors 6<1>, 5<1> for braking and starting the motor to which it relates. The system is described as applied to centrifugal extractors for laundries in which a door 14' is closed to start the machine. This operation closes switches 34', 37<1> the latter energizing the starting and running contactor 5'. This circuit includes an emergency stop switch 16<1>, a timer 10' driven by the machine and determining the length of run, and the contact 19<b> so that if the demand of another machine is abnormal the machine cannot start. The contactor 5<1> in closing makes its own maintaining circuit which includes the switch 34<1> and the switches 16<1> and 10'. It also closes a circuit for a forward relay 7<1> which extinguishes a ' stop ' indicator lamp on the machine makes its own maintaining circuit and prepares a circuit for the reversing (braking) contactor 6<1>. When the door is released it is latched closed with the switch 34<1> only in closed position, this controlling the circuits of the contactors 5<1> and 6<1>. The forward and reverse relays 7' and 8<1>, a magnetic releasing device for the latch 13<1> and lighting a ' run ' indicator lamp 11'. The timer 10<1> eventually opens the maintaining circuit of contactor 5<1> and the opening of this completes the circuit of the reversing (braking) contactor 6<1> which includes the contact 19<a> so that braking current cannot flow unless the demands of all other machines are below the limit. The contactor 6<1> in closing makes its own maintaining circuit, which includes a friction driven switch 9<1> closed so long as the motor is running forwards. The circuit of the reverse relay 8<1> is also closed by the contactor 6' and this makes its own maintaining circuit and prepares a circuit for the latch releasing magnet 13'. As soon as the motor runs backwards the switch 9<1> opens opening the contactor 6<1> which completes the circuit for the latch magnet 13<1>. The door 14<1> is thus released and switch 34' opens to de-energize the relays 7<1> and 8<1> and extinguish the run lamp 11<1>. The 'stop ' lamp 12<1> lights on the de-energization of relay 7<1>.