GB681776A - Improvements in the remote control of multiphase electric motors - Google Patents

Abstract

681,776. Control of motors. BROOKE, W., and BALDWIN, H. T. Nov. 4, 1950, No. 26985/50. Class 38 (iii) Relates to a system comprising a remote control switch D having "off", "start", and "run" positions, means being provided to prevent an overload control from being rendered ineffective when the control switch is held in the starting-position. When the supply is switched on to lines L<SP>1</SP>, L<SP>2</SP>, L<SP>3</SP>, and the control switch is in the "off" position D', relay B is energised through a common trip bar H of overload relays E, F, G, and through contact A<SP>3</SP>. The closure of contact B<SP>3</SP> maintains the relay B energised independently of the contact A<SP>3</SP>. Upon movement of the switch D to starting-position D<SP>2</SP>, a relay A is energised from a transformer T through rectifier K, a main contactor C then being closed through contacts A<SP>2</SP>, B<SP>2</SP>. The switch D is then allowed to move to the running position D<SP>3</SP> whereupon a resistor L is connected in series with coil A<SP>1</SP> so allowing the relay A normally to remain closed, but not permitting reclosure if the power supply is re-instituted after failure and the switch D remains in its running- position. If the motor is over-loaded and at the same time the control switch is held in the position D<SP>2</SP>, the trip bar H opens to de-energise relay B. Opening of contacts B<SP>2</SP> de-energises contactor C to stop the motor although relay A remains energised. Reclosure of the overload control does not re-energise relay B since contacts A<SP>3</SP>, B<SP>3</SP>, are open, it being necessary to return the control switch to the position D<SP>1</SP> in order to re-start the motor.