Patent GB-704873-A (GB)
Title: Improvements in electric motor control systems for winding engines and the like
Inventor: PETCH THOMAS HAYES
IPC: B66B1/12
Filed: 1950-12-14
Abstract: 704,873. Control of D.C. motors. BRITISH THOMSON-HOUSTON CO., Ltd. Aug. 22, 1951 [Dec. 14, 1950], No. 30532/50. Class 38(3) A D.C. motor M for driving a winding engine is supplied from a generator G having an exciter GE, and is regulated by a master controller MC which has a handle HL. The system comprises cam gear for a double-drum winding engine similar to that described in Specification 620,236. Shafts 10, 11, Fig. 2, are driven from separate drums and in turn drive cams 14, 15, and 16, 17, which are engaged by rockers 18, 19, and 20, 21. Rockers 18, 21, and potentiometer PR1 are operated by a thrustor T2 (such operation being limited by the cams). The thrustor T1 actuates rockers 19, 20, and a potentiometer PR2 in a similar manner. When the operating handle is moved in the direction for forward rotation contacts 41, 43, 45, 47, are closed and the slider of a face-plate PR3 is adjusted to increase the voltage applied to field winding GEf1 of the exciter GE. A coil Ha is energized to close the circuit to thrustor T1 which then rises slightly to take up the clearance between cam rocker 19 and cam 15, and to move the arm of potentiometer PR2. The handle may then be moved directly to the full-speed position, so applying full voltage to the field winding GEf1 the potentiometer PR2 is however in such a position that full generator voltage is applied to the circuit comprising potentiometer P, rectifiers R1, R2, and the exciter field winding GEf3. Current therefore flows through, rectifier R1 against the separate bias potential across the potentiometer P, and the field winding,GEf3 is energized to oppose the winding GEf1. The voltage of the generator G is therefore restricted to a value dependent upon the position of the potentiometer PR2, and as the slider of this potentiometer is carried along by the thrustor T1 a continuously increasing generator voltage is permitted before the opposing effect of the field winding GEf3 becomes operative. Towards the end of the wind the cam 15 forces back the thrustor T1 and the winding GEf3 becomes effective at decreasing voltages so that the speed is automatically reduced. Operation in the reverse direction is similar to that described. The potentiometer resistor PRa may be connected across the exciter GE or across a tachometer generator driven by the main motor. Further, the resistor PRa may be fixed and the points of connection of the rectifiers R1, R2, to the potentiometer P made adjustable. The thrustor may have time-lag devices so that the rates of acceleration and deceleration can be controlled at times when the cams are not effective, as when starting or stopping in mid-wind. The exciter GE may have a field winding GEf2 which opposes the winding GEf1 and is responsive to the generator voltage. This additional winding does not become effective, however, until the generator has reached its full voltage. In another arrangement, Fig. 3 (not shown), the potentiometer resistor PRa is omitted and the windings GEf1 and GEf3 are replaced by a single field winding. In this modification the voltage-limiting circuit comprises a potentiometer rheostat connected across a constant D.C. source and having moving contacts operated by the cam and thrustor mechanism and connected through oppositely poled rectifiers, the common point of the rectifiers and the mid-point of the rheostat being connected in parallel with the control field winding of the exciter. Specifications 588,209 and 591,238 also are referred to.