GB438431A - Improvements relating to automatic electromagnetic cut-outs for controlling electric circuits - Google Patents

Abstract

438,431. Variable speed generator systems. C.A.V.-BOSCH, Ltd., WOOD, N. R., and WATERS, A. V., Warple Way, Acton, London. May 16, 1934, No. 14758. [Class 38 (iv)] In an automatic electromagnetic cut-out for use in battery charging systems having shunt and series windings which normally assist each other but oppose with reverse current from the battery to cause the opening of the cutout contacts, in order to render the cut-out more sensitive to reverse current, a resistance is automatically inserted in series with the shunt winding after the closure of the cut-out contacts, said resistance being controlled by separate contacts which are operated by the action of a separate electromagnet. As shown in the Figure the cut-out contacts a are closed by the shunt winding b connected across the dynamo d when the voltage of the latter exceeds a predetermined value, a series coil c having its circuit included with that of a battery e on closure of the cut-out contacts. After the operation of the cut-out when a further increase of dynamo voltage occurs a second electromagnet f causes the opening of contacts g normally short-circuiting a resistance h in the circuit of the shunt winding c of the cut-out. The introduction of this resistance reduces the energization of the cut-out and increases its sensitivity to reversals of current in the coil c. Thus at the commencement of any current reversal the cut-out immediately comes into operation to prevent any motoring of the dynamo such as might occur, particularly, in cases in which there is a freewheel device between the engine and transmission of a motor vehicle on which the cut-out is employed. In a modification the resistance is brought into circuit immediately a reversal of current occurs by the action of a polarized relay.