GB216807A - Improvements in or relating to electric braking mechanism - Google Patents

Abstract

216,807. James, H. V. Dec. 18,1923. Dynamos, regulating; motors, controlling.-In an electric braking system for printing, papermaking, and textile machines, a dynamo 35, mechanically coupled to the driven machine, is adapted to set up an E.M.F. counter to that of the mains M feeding the brake-energizing coils 42 so that, as the machine slows down and therefore also the dynamo, the back E.M.F. of the dynamo opposing the line voltage falls and gradually produces a corresponding increasing E.M.F. across the brake-energizing coils. The Figure shows the circuit when the machine is stationary. To start the motor 2 driving the machine, a switch 33 is closed. Current flows from the positive main N through leads 1, 25, switch 29, lead 30, solenoid 31, lead 32 to the negative main N. The solenoid 31 operates a switch 47 and closes the driving circuit for the motor 2. To stop the machine the switch 33 is opened. The solenoid 31 is then de-energized and switch 47 opens, breaking the connection to the mains and establishing a circuit through the motor 2, lead 10, coil 18, lead 20, switch 24, leads 21, 3, back to the motor. The solenoid 18 closes a switch 40 and completes a circuit from motor 2, lead 10, brake resistance 11, switch 46, coil 15, lead's 16, 3 back to the motor. The coil 15 assists in holding the switch 46 closed. As the E.M.F. across the motor 2 decreases, the coil 18 becomes de-energized, but the coil 15 remains energized until the motor is stationary and holds the switches 41, 46 closed. The former switch closes a circuit through dynamo 35, lead 38, switch 41, lead 44, brake coils 42, 43 and lead 45. The dynamo 35 is wound so that, with the machine running at full speed, the E.M.F. generated is equal and opposite to that of the mains. If the switch 33 is opened while the machine is at full speed no energy initially flows through the brake coils 42, but as the armature 35 comes to rest its back E.M.F. decreases until, when it is stationary, the back E.M.F. is nil and the energy through the coils is that due to the full main voltage. Instead of using a separate dynamo 35 the motor 2 may be suitably wound and used. Specification 218,922, [Class 38 (iii), Electric motor control systems &c.], is referred to.