GB438374A - Improvements relating to direct current electric motor equipments operated in connection with rotary direct current transformers - Google Patents

Abstract

438,374. Rotary transformers. PRITT, S. E., Riverdale, Hathersage, near Sheffield, GRAY, W. T., Darroch, The Close, Altrincham, Cheshire, and ASSOCIATED ELECTRICAL INDUSTRIES, Ltd., Crown House, Aldwych, London. May 16, 1934, No. 14841. [Class 35] [See also Group XXXVII] In a system in which motors are supplied from a metadyne transformer 1, Fig. 1, switching means 8, 9, are provided whereby the connections of a variator winding 2, or the field 4 of an exciter 3 supplying a variator winding, to the brushes of the transformer can be changed at suitable points during the motoring or regenerative operation, so that a rising, falling, or constant voltage may be supplied to the variator winding. For acceleration the switch 9 is closed so that at first a rising voltage is applied to the variator winding from the brushes c, d, and, when the, voltage between the brushes b, d, is zero switch 9 is opened, and switch 8 closed, so that a falling voltage from brushes c, b, is then applied, similar switching operations being effected during regenerative deceleration. By including a resistance in the connection to the brush d the switching change may be made even though a voltage difference exists between the brushes band d. In a modification, Fig. 2, the brushes b, d, are connected by a resistance 10 through switches 13, 14, the exciter field winding 4 being connected to an intermediate point 11 of this resistance through an additional resistance 12 which may be short-circuited. In a further modification Fig. 3 (not shown), the brush d is permanently connected to the exciter field winding through a resistance, and direct connection is made to the brush b by means of a switch. The changes of connections may be made manually or by means of relays operating when the motor voltage attains a desired amount. In place of switches, rectifiers may be connected between the brushes b, d, and the exciter field so that the effective connections are automatically transferred. Specification 400,416, [Group XXXVII], is referred to.