Patent GB-393371-A (GB)
Title: Improvements in and relating to electric motor control systems
IPC: H02P7/34
Filed: 1932-02-15
Abstract: 393,371. Control of D.C. motors; actuating controllers. INTERNATIONAL GENERAL ELECTRIC CO., Inc., 120, Broadway, New York, U.S.A.-(Assignees of Allgemeine Elektricitats-Ges. ; 2, Friedrich Karl-Ufer, Berlin.) Feb. 15, 1932, No. 4451. Convention date, Feb. 14, 1931. [Class 38 (iii).] The generator field regulator 16 in a Ward- Leonard system is fluid-operated, and a controlling valve 38 actuated by two electromagnetic systems 19, 20, influenced by load and control currents, is maintained in a neutral position by springs 35, 36, when the electromagnetic systems exert equal forces. When a master controller 42 is moved to the left, a coil 481 is first energized to cut out a resistance 28 in the motor field circuit 4, and in position 1 a contactor 26 is energized to connect the generator field 2 to an exciter PN through all of the regulator resistance 16. The controller 42 is then moved quickly to its third position whereupon a coil 23 on the magnet 19 is energized to move the valve 38 downwards, and the regulator 16 is driven to short-circuit progressively, the generator field resistance. The movement of the regulator is controlled in accordance with the motor current by means of coils 21, 22 on the magnets 19, 20. The coil 21 opposes the coil 23 so that, as the armature current increases, the speed with which the regulator 16 is moved decreases, or in the event of the armature current rising sufficiently for the coil 22 to overcome the difference effect of the coils 21, 23, the regulator movement may be reversed. If constant speed operation is required, the controller 42 is returned to position 2 to de-energize the coil 23, and springs 35, 36 return the valve 38 to its " off " position. To stop the motor 3, the controller 42 is returned to the zero position. Between the positions 0, 1, a coil 24 is energized through a sliding contact 53 on the regulator 16, and the valve 38 is operated to return the regulator to its zero position. When the controller is in position 0 the contactor 26 is de-energized, and the field circuit of the generator opened to stop the motor 3. If the controller 42 is moved quickly into the zero position the contactor 26 remains energized through the contact 53 until the regulator 16 reaches its zero position. For rapid stopping, the controller 42 is thrown to the first position to the right with the result that, when the regulator 16 has reached its zero position, the contactor 26 opens, and a contactor 25 closes to reverse the generator field 2, the regulator 16 being held in its zero position by a sliding contact 52, and the coil 23. If the controller is thrown from one extreme position to another the braking operation is controlled by the regulator 19, 20, 38. With the controller 42 between the zero and first positions right or left, the regulator 16 is maintained in its zero position despite leakage, by means of coils 23, 24, and contacts 52, 53. The regulator may control an exciter supplying the field of the Ward-Leonard generator. The Specification as open to inspection under Sect. 91 comprises also an arrangement in which the regulator is operated by an electric motor which is stopped or reversed under the control of the load current, or the acceleration of the main motor. This subject-matter does not appear in the Specification as accepted.