GB619611A - Improvements in or relating to electrical frequency controlling devices - Google Patents

Abstract

619,611. Automatic control of frequency ; systems depending on two machines ; dynamoelectric machines. GENERAL ELECTRIC CO., Ltd., and FRIEDLANDER, E. S. Dec. 16, 1946, No. 37014. [Classes 35 and 38 (iv)] [Also in Group XXXVII] A constant frequency supply 19 is obtained from a source 3 of varying frequency, from the rotor 4 of an induction type frequency converter having a rotatable stator 2 supplied by the source 3, frequency responsive means being arranged to control the relative speeds of rotation of the stator and rotot to correct for deviation of output frequency. As shown in Fig. 1, a motor 8 drives the stator at constant speed and the rotor through a variable speed drive 10-12, the speed controlling member 11 of the drive being actuated by a worm 15 operated by a split-phase reversible motor 14 -controlled by a wattmetric type relay 23, 24, which is energized from supply 19 through a constant voltage transformer 7 and which is associated with a resonant circuit 25, 26 tuned to the normal output frequency. At normal frequency the relay contacts are open and motor 14 de-energized, but increase or decrease of output frequency causes a torque to be exerted on the driving system of the relay in such a direction as to start motor 14 running in the appropriate direction to correct the deviation. In a modified arrangement, both rotor and stator of the converter are normally stationary, but are rotatable by separate motors, when frequency correction is necessary, under the control of the frequency responsive relay.