GB553192A - Improvements in electro-magnetic slip couplings - Google Patents

Abstract

553,192. Electromagnetic clutches. ENGLISH ELECTRIC CO., Ltd., CARNEGIE, H. S., and AYRES, W. E. M. Jan. 28, 1942, No. 1204. Addition to 544,941. [ Class 35] An electromagnetic slip coupling has various arrangements for decreasing or eliminating the reduction in magnetic flux. due to the secondary current reaction, which occurs when the slip increases. In one form, the magnetic system is saturated, so that the flux is unaffected by changes in the secondary current. In another, the primary element 4a, Fig. 1, has two spatially displaced windings, one of which is fed through resistance 14 with a constant current from shunt-excited generator 11, while the other is fed through resistance 15 with a current dependent on the secondary current, through transformers 10 and rectifiers 8. This second component wholly, partially or over-compensates the secondary reaction flux. The primary element may have either a distributed drum winding, or salient poles ; the secondary has sliprings connected to fixed or variable resistance 5. Finally, in the form shown in Fig. 2 a bucking or boosting exciter 7 is connected in series with the primary winding and the field winding 7a of this exciter is in series with a sub-exciter 12 running on the output shaft. A rectifier 13 is in series with the winding 7a so that excitation occurs only if the voltage generated by 12 exceeds the supply voltage. The result is that the exciter 7 is effective only over a certain range of slips, e.g. up to a predetermined maximum. The rectifier 13 may be omitted if the exciter 7 is of the kind in which saturable shunts divert flux from the field magnets until a predetermined excitation is reached. Where the control does not depend on secondary current, the secondary member may be a squirrelcage or of the unwound type. Specification 517,468 is referred to.