Patent GB-405720-A (GB)
Title: Improvements in and relating to systems of electric motor control
IPC: B60L15/04
Filed: 1932-08-22
Abstract: 405,720. Master control of D.C motors ; actuating controllers. BRITISH THOMSON-HOUSTON CO., Ltd., Crown House, Aldwych, London.-(Assignees of Tritle, J. F. ; 507, Seminole Drive, Erie, Pennsylvania, U.S.A.) Aug. 22, 1932, No. 23493. Convention date, Aug. 21, 1931. [Class 38 (iii).] A series - parallel acceleration controller is actuated by fluid pressure means having a fluid throttling device, and a relay having a main current winding, and a winding controlled by means associated with a master controller, is provided for controlling a stop mechanism which arrests the retarded operation of the accelerating controller. The invention is described as applied to a series-parallel system such as described in Specification 188,471, [Class 38 (iii), Electric motor control systems &c.]. To initiate forward acceleration, a control switch 80 is moved to the left, a direction master controller Cl is moved to its forward position, and a master controller C2 is moved to its series position S, so that a reversing switch 34 is moved for forward operation and a self-maintaining main circuit-breaker LB is closed. The circuit-breaker LB in closing also energizes a contactor S and a valve operating electromagnet 68, the contactor S connecting the motors A1-A4 in series parallel with all resistance R1-R5 and R7-R10 in circuit, and the electromagnet 68 opening a valve for the admission of fluid under pressure to incompressible fluid in a container 73. The fluid passes from the container 73 through an adjustable orifice 77 to operate on a piston 61 and rotate the controller C3. The controller cuts out the series resistance in steps as it moves from position 1 to position 9<a>. The main motor current passes through the windings AR1, AR2, of a relay AR which has an additional winding AR3 energized from the line through an adjustable resistance R13 when the master controller C2 is in position S, and which is normally not closed by the action of these three coils. As the controller C3 is moved a pawl 82 is vibrated by a notched wheel 81, and a spring bias, so that contacts 103 are periodically closed to connect the coil of an electromagnet 83 acting on and assisting the spring bias of the pawl 82, in parallel with the resistance R13, so as to periodically increase the energization of the winding AR3. When the cumulative effect of the coils AR1, AR2, AR3 exceeds a certain amount the relay AR closes against the action of an adjustable spring 37 to connect a resistance R14 in parallel with the winding AR3 as long as the contacts 103 are closed. This reduces the energization of the coil AR3 and increases that of the electromagnet 83, the relay AR being now controlled primarily by the motor current. The relay AR remains closed if the motor current is excessive so that when the pawl 82 next engages a notch on the wheel 81, the electromagnet 83 energized through the resistance R14, mechanically locks the controller from further movement until the motor current falls. At each accelerating step the contacts 103 are closed to increase the energization of the coil AR3, so that at each step the relay AR is placed in condition to remain closed to continue the energization of the electromagnet 83 to stop acceleration until the motor current falls, or is dropped out upon opening of contacts 103 to allow further acceleration. To continue acceleration with parallel connections for the motors the controller C2 is moved to the position P to energize switches G, P, which de-energize the switch S and the electromagnet 68 and connect the motors in parallel with resistance in series. The valves operated by the electromagnet 68 then allow fluid to act on the piston 60 and move the controller to its original position under the action of the pawl 82 and the relay AR which, however, is now deprived of the force of its coil AR3 so that the parallel acceleration is greater than the series. If a high acceleration is required throughout both phases of control the controller C2 is moved directly to its position P. At any time in the control the acceleration may be stopped by moving the controller C2 to position SW to energize the electromagnet 83 from the line through resistance R14 and lock the controller by its pawl.