Patent GB-476398-A (GB)
Title: Improvements relating to electric rotary converters and converting systems
IPC: H02K47/16
Filed: 1936-07-17
Abstract: 476,398. Rotary transformers. MACFARLANE, J. C., and MACFARLANE, W. A. July 17, 1936, Nos. 19829/36 and 11619/37. [Class 35] [Also in Group XXXVII] A machine for transforming a constant voltage supply to a variable voltage, variable direct current supply comprises (1) a field structure having 2n poles of which n poles M belong to the primary or motoring circuit, and n poles G to the secondary or generating circuit ; (2) an armature having a winding with a span corresponding to a 2n pole field, the main excitation be ing provided by armature reaction due to the prim ary and secondary currents ; (3) 2n interpoles K each having a winding 3 in the primary circuit and a winding 4 in the secondary circuit ; (4) windings. 1 on the secondary poles G connected across the primary supply and assisting the armature reaction due to the primary current ; (5) opposing windings 2 on these poles connected in series with the secondary circuit ; and (6) a compounding winding 5 on the primary poles M assisting the armature reaction due to the secondary current. The winding 5 may be connected to a constant voltage source, for example, the primary supply E, across the secondary voltage e, or in series either with the primary or with the secondary circuit. The primary poles M may also carry windings, one opposing the other. Fig. 5 shows a system employing the transformer CA to feed a motor MA which may drive a winch, crane, &c., preferably with the expenditure of constant horse-power. The transformer has starting coils 7 on the primary poles, these coils being of high resistance or connected in series with a resistance. A potentiometer resistance 16 supplying the field 8 of the motor has on its operating shaft a cam 15 which in the neutral position shown closes a circuit from the mains through a contactor coil 11, and field windings 1, 5. Coil 1 at this stage is short-circuited at contacts 14B so that with the switches 22 closed, the machine runs as a motor without generating any secondary voltage. As soon as the current in the coil 11 reaches its full value, the starting winding 7 is short-circuited through the contacts 10B. Movement of the handle 19 in the hoisting or lowering direction opens the contacts 12, but the circuit of the contactor coil 11 is maintained by the contacts 1OA; at the same time contacts 14B open, removing the short-circuit from the winding 1, and contacts 14A close, giving a supply to the potentiometer regulator 16, to the field winding 9 of a regulating motor RA in series with the motor field winding 8 and to the brake coil 17 which releases the brake. The strength and direction of the current in the field winding 8 of the motor MA are determined by the position of the regulator handle 19. Excessive speed of the motor in the load lifting direction is prevented by the reduction of torque due to the field opposing action of the regulating machine RA. If the handle 19 is returned quickly to neutral with the motor running at high speed, coil 13 connected across the brushes of the regulating machine prevents the contactor 14 from falling into recess 21 until the speed has dropped to a low value, thus maintaining a supply to the potentiometer and the brake coil and permitting the motor to regenerate. If the plant is shut down at the main switch 22 before returning the handle 19 to neutral, the brake immediately sustains the load and subsequent closure of the switch 22 allows the transformer to start up and run at moderate speed on the starting coil. 7. Since contacts 12A and 10A are open, no voltage is applied to windings 5, 9 and coils 1, 8 and 17 so that the motor can exert no torque, and the handle 19 must be returned to neutral position for a restart. In a modification, the coils 9, 17 are in series in the transformer output circuit. In a further modification, the compounding coil 5 on the transformer motoring poles is replaced by a coil carrying the secondary current. To provide a field until the secondary current has become established, the motoring poles have an additional winding connected across the primary supply and short-circuited by additional contacts on the switch 14 when the short-circuit across the coil 1 is removed ; known delay or interlocking devices may be used to delay the closing of these additional contacts. The speed of the motor MA may be further controlled by separately controlling the excitation of the regulating machine, the poles of which may have compound windings excited with the primary or secondary voltage or current. Specifications 308,041, [Class 35], and 405,759 are referred to.