GB226887A - Improvements in and relating to systems of electric motor control - Google Patents

Abstract

226,887. British Thomson-Houston Co., Ltd., and Hastings, H. C. Oct. 3, 1923. Controllers, actuating; master control systems. -In an electric motor control system of the kind described in Specification 204,105, a master controller M controls a pilot motor N, which operates a drum or cam-shaft controller for the main motors, and the field of which is weakened when it is returning the main controller to its " off " position so as to have a higher speed of movement than when it is moving the main controller to the " full on " position. Associated with the main controller is a drum having contact segments G, K, Y, for controlling auxiliary apparatus. The potential relay P can only close when the main controller is " off " and segment Y engages contacts P<1>, P<2>, the closing current passing through a resistance 80, once closed it will hold on with the current that can pass through both the resistances 80, 81. Movement of a switch 58 to the right sets an overload relay O, and movement to the left energizes the controller M. Movement of the controller M to position 1 energizes either coil 4 or 5 of a reverser according to the position of a master reverser A, line-brealer coils 62, 63 then become energized closing the main motor circuit in its first series position, and also moving associated bridge contacts Z &c. away from the position shown in the Figure, thereby completing the circuit of the pilot motor N which is prevented from running for its armature is shorted by a relay 69 spring biased to the closed position. Movement of controller M to position 2 causes energization of coil S of relay 69 thereby removing the short from the pilot motor N so that it operates the main motor controller. Energization of coil S is dependent upon an accelerator relay C of the type described in Specification 144,612. Segments G maintain the energization of the coil S between successive steps of the main controller so as to ensure that the motor N does not stop between steps, de-energization of relay S causes the motor N to be braked for its armature is shorted while its series field is maintained. The main controller advances to the full series position and remains there till controller M is advanced to position 3 whereupon it moves step by step to the full parallel position. In this position segment K runs off contact 12 interrupting circuit of motor N, which is now stopped by spring actuated brake L. Movement of the controller M to the " off " position or operation of either relay 0, P causes de-energization of coils 62, 63 and consequent return of the contacts Z &c. to the position shown, thereby reversing the circuit of the pilot motor N and shorting part of its field by contact Z bridging fixed contacts 76, 77. the motor N thus returning the main controller to its off position at high speed. The main controller effects the usual series-parallel connections. An advancer B is provided to eause advance of the main controller irrespective of the accelerator relay C.