Patent GB-436574-A (GB)
Title: Improvements in or relating to the automatic frequency regulation of alternating current supplies
IPC: H02J3/08
Filed: 1934-01-13
Abstract: 436,574. Automatic reversible motor regulators. GENERAL ELECTRIC CO., Ltd., Magnet House, Kingsway, London, and GIBSON, J. W., c/o General Electric Co., Witton, Birmingham. Jan. 3, 1934, No. 238. [Class 38 (iv)] The frequency of an A.C. supply is controlled by means responsive to integrated frequency error and means are provided responsive to the frequency becoming correct which cancel or reduce the regulating effect of the means responsive to integrated frequency error. The frequency is varied by a reversible motor 54 acting on the engine governor under the control of contactors 49, 50, which are operated by " raise " and " lower " segments 40, 41 on a drum switch 38 which is rotated by a synchronous motor 29 driven by the generator. The brush 44 coacting with a continuous segment 39 on the switch 38 is energized from supply 19 through contacts 14 of a telephone relay which are closed intermittently by a master clock 3 so that when the frequency is correct the contacts of relay 14 are not closed when the brushes 45 and 46 are on their respective segments 40, 41. Positive or negative integrated frequency error causes contacts 46, 41 or 45, 40 to be closed at the same instant as contacts 14 are closed thereby to control the governor motor 54 to decrease or increase the speed of the prime mover. The control is modified in response to the instantaneous value of frequency by means of contacts 35, 36 actuated through a slipping clutch from the planet shaft of a differential gear 26, one element of which is driven by a synchronous motor connected to the generator and another of which is driven from a motor 1 the speed of which is maintained constant by the master clock 3. The contacts 35, 36 may be in series with the corresponding contacts of the controller 38 so as to provide an over-riding control when the frequency is correct, or they may be in parallel wth the corresponding contactor coils 53, 48 through a relay coil which controls a resistance in the circuit of the motor 54 so as to retard its action when the frequency is correct although integrated frequency error occurs. The arm carrying the brushes 44, 45, 46, 47 of the controller 38 is adjustable in accordance with the position of the governor through the medium of torque motors 59, 60 and the arrangement allows of an integrated frequency error dependent upon the generator loading. This ensures suitable load sharing between parallel connected generators. The contacts 35, 36 responsive to frequency may alternatively control, through solenoids, a differential gear connected between the torque motor 60 and the brush arm so as to modify the action of the controller 38 when the instantaneous value of the frequency is correct. Lock nut contacts 42, 43 on the controller 38 effect control of warning or protective devices when the integrated frequency error exceeds a predetermined value. Interlock contacts 51, 52 are provided on the contactors 49, 50. The speed of the motor 1 is maintained in fixed relation with a clock 3 by control of a field rheostat 4 by a reversible motor 5 whose fields 21, 22 are controlled by brushes 8, 9, 10 and segments 11, 12, 13 on a controller driven from the motor 1 to be controlled. The main segment 11 is energized intermittently through a relay 15 from the contacts of the clock controlled relay 14 so that an deviation of the motor speed from the desired value brush 9 or 10 contacts with the corresponding segment when relay 15 is closed and thereby energizes the motor 5 to raise or lower the speed of the motor 1. To prevent hunting the arm on which the brakes are supported is moved with the arm of 24 the field resistance 4. The differential gears described may be replaced by equivalent electrical devices. Specification 407,401 is referred to.