Improvements in power transmission by dynamo-electric machines
550,590. Transmitting mechanical power. ENGLISH ELECTRIC CO., Ltd., and CARNEGIE, H. S. June 11, 1941, No. 7397. [Class 38 (iv)] An electromagnetic coupling, of the kind in which torque is transmitted by the electromagnetic interaction between a field system and a secondary system in which the field induces current during continuous slip, is combined with a dynamo-electric generator and a motor element whereby the rotation of the output shaft may be reversed with or without changes in speed ratio. Fig. 1 shows a shaft 1 carrying two field elements 5, 7 the first forming with a secondary element 6 on a shaft 2 an electromagnetic coupling and the second co-operating with a stator 8 to form an alternator supplying current to a motor stator 10 co-operating with a rotor 11 on the shaft 2. Various structural arrangements of the elements 7, 8, 10, 11 are possible and the motor or generator may constitute separate machines in driving association with the shafts. The electrical control comprises primarily a switch 13 for selective energization of the field elements and may comprise a switch 15 whereby in successive positions (1) a forward drive, (2) braking by application of D.C. to the .motor stator, and (3) reverse drive are obtained. A pole changing switch 17 may give a change of speed. Other methods of braking may be used. The generator may be a synchronous alternator and the motor an induction motor or synchronous-induction motor.