GB702941A - Improvements relating to electrically propelled vehicles - Google Patents

Abstract

702,941. Control of A.C. motors. ENGLISH ELECTRIC CO., Ltd. June 6, 1952 [June 15, 1951], No. 14218/51. Class 38(3) An electrically propelled vehicle includes, in combination, driving means consisting of at least one single phase commutator motor 1-4; a transformer 5 for supplying current to the driving means, the secondary winding of the transformer being divided into at least two sections one of which is provided with a plurality of tappings, and switch means arranged to be operated in the following sequence so as to accelerate the vehicle:- a) to select tapping points on the secondary winding of increasing voltage b) to select a low voltage tapping on the transformer c) to insert an untapped section of the secondary winding in the circuit, and d) to again select tapping points of increasing voltage, and so on until the whole of the secondary winding is in circuit with the driving means. In the OFF position contactors 12, 19 only are closed. The selection of the increasing voltage tapping points is effected by the cam-shaft operated contactors 12-16 and 18, alternate tappings being connected to opposite ends of an impedance 17 which ensures that, when changing from one contactor to another, the supply is not removed from the motors. Contactor 18 is alternately closed and opened so as to avoid short-circuiting a part of the secondary winding when two adjacent contactors are closed at the same time. When inserting an untapped section into circuit-say the section between taps 5a and 5b-contactor 21 is first closed so that the section is brought into circuit with a resistor 24 in series to limit the current. Contactor 20 is then closed and contactor 21 opened to thereafter remove the resistor. Contactors 22, 23 are similarly operated. Reversing and overload devices are also provided.