GB624684A - Improvements in and relating to the control of electric motors driving winding engines, hoists and the like - Google Patents

Abstract

624,684. Control of D.C. motors. BRITISH THOMSON-HOUSTON CO., Ltd., PETCH, T. H., and LIDDIARD, H. W. C. Sept. 5, 1944, No. 16944. Addition to 577,183. [Class 38(iii)] In the control system described in the parent Specification the amphidyne exciter 5 is provided with an additional field winding 21 which is connected to the rectifiers 11a, 11b, across a resistance 22. An energy-storage device such as the separately-excited motor 13 with a fly-wheel 14 is connected in series with the resistance 22 across the armature of the exciter 5. For low rates of change of the excitation of the field 6, the voltage-drop across the resistor 22 will not be sufficient to break down the forward resistance of the rectifiers and the field 21 will be ineffective. For higher rates of change, one of the rectifiers will pass a current to the field 21, which acts in opposition to the field 6 and controls the exciter output. Additional control neans comprise a condenser 23 connected in series with a resistance 24, which shunts a relay-coil. A sudden change in the exciter armature voltage will energize the coil 25 to close contacts 26 and short-circuit the rectifiers. An alternative arrangement comprises a transformer, the primary winding of which is connected across the armature of the exciter, and the secondary connected through the rectifiers to the additional field. The main generator may carry a secondary winding which acts similarly to the transformer secondary winding.