GB541825A - Improvements in electromagnetic couplings for the transmission of mechanical power - Google Patents

Abstract

541,825. Electromagnetic driving-couplings. ENGLISH ELECTRIC CO., Ltd., CALVERLEY, J. E., and CARNEGIE, H. S. Aug. 27, 1940, Nos. 13529/40 and 9795/41. [Class 35] In an electromagnetic coupling in which torque is transmitted by the inter-action of a primary field system on one half of the coupling with a secondary system on the other half in which current can be induced by movement thereof relatively to the field system, means are provided for varying at will the relative rotation of the secondary system and a magnetic field with which it is linked, the variation being independent of the rotation of the primary and secondary systems. As shown in Fig. 1, one half 1a of the coupling transmitting power from a motor 8 to a shaft 9 comprises a magnet core similar to the armature of a D.C. machine with the windings connected to slip rings 1 b and to a commutator 1c. The other half 1d, forming the secondary system, comprises a magnetic core surrounding the armature and carrying a secondary winding connected to slip rings and with its circuit closed through a variable resistance connected across the brushes ; alternatively a squirrelcage secondary winding may be provided, or no winding at all. In normal running D.C. is supplied to the primary winding through brushes 2 and slip rings. By throwing over the switch 4 and supplying the brushes 3 the primary magnetic field will become stationary and effect a retarding action on the secondary winding which action may be varied by rotation of the brushes 3. In another form, the commutator may be omitted and the switch 4 effect a change from D.C. to an independent and constant frequency A.C. supply, the primary being a multi-phase winding ; the D.C. supply may be omitted by making the A.C. supply of variable and controllable frequency. Or the brushes 2 may change from one constant frequency A.C. supply to another. The form shown in Fig. 3 includes a tertiary system 1e which is stationary and has field windings connected to a D.C. supply by the switch 4. In a modification, the field windings on the tertiary system are supplied with D.C. through a commutator and relatively rotatable brushes when the switch is operated. In a further modification the switch disconnects the brushes from D.C. and connects the field windings of the tertiary system to A.C. of two or more phases of variable and controllable frequency ; the switch may be a three position switch to connect the field winding of the tertiary system to either of two such A.C. supplies of different frequencies. With the motor 8 at rest the shaft 9 may be driven by rotating the brushes 3, Fig. 1, while connected to the supply or by rotating the tertiary system in the other forms while excited.