GB183503A - Improvements in and relating to electric control systems - Google Patents

Abstract

183,503. British Thomson - Houston Co., Ltd., (General Electric Co.). Feb. 21, 1921. Regulation, automatic systems and apparatus for; dynamos and motors combined for transmitting power.-An electric control system in which alternating-current motors are supplied includes a device depending upon the current and voltage of the supply and unaffected by change of supply frequency, for indicating directly that the motors are operating near their point of maximum torque, or for regulating the system so that the motors are maintained operating near that point. In the automatic regulating-arrangements shown the device controls the excitation of an alternator supplying a motor. When used simply as an indicator, the pointer of the device moves freely to one side or the other of a scale. and the necessary regulation is effected manually. In the arrangement shown in Fig. 2 a current coil 17 and a voltage coil 20 of high inductance or, as shown, in series with a relatively high inductance 25, act differentially upon vanes 22, 23 mounted on a spindle carrying a contact-making pointer 14 which closes the circuit of a reversible motor 33, the shaft of which operates to vary a rheostat 30 in series with the alternator field 29. In another arrangement the current and voltage coils act on cores mounted on the contact-making spindle, and the rheostat 30 is in series with the exciter field 32. Instead of vanes or cores, short-circuited cores may be carried on the contact-making element, these coils being positioned with their axes displaced from one another so that opposing torques are produced by the current and voltage elements. In another arrangement, shown in Fig. 5, the pilot motor is omitted and the contactmaking member shunts a relatively small resistance 55 in series with the exciter field and resistance 56, the later mechanism being so proportioned with respect to the former that the motor is maintained operating near its point of maximum torque.