GB644607A - Improvements in and relating to electric motors - Google Patents

Abstract

644,607. Exciting dynamo-electric machines. PESTARINI, J. M. Sept. 22, 1947, No. 25685. Convention date, Sept. 20, 1946. [Class 35] The primary variator winding or windings of a metadyne motor having short-circuited secondary brushes, is excited with a constant component of excitation and a component produced by an auxiliary dynamo with a saturated magnetic field and excited by a constant component and a component derived from the voltage across the primary brushes of the motor. The primary brushes a, c are connected directly or through compensating windings to terminals A, C, connected to the supply 3, 4 whilst the terminals B, D, of the secondary brushes b, d, are short-circuited. A variator winding 5 is separately supplied and controls the extent of the motoring or regenerative action of the machine. In order to produce a characteristic having a sharp bend into regenerative operation at any particular speed a variator winding 13 is, fed from a saturated auxiliary dynamo 12 driven separately or from the metadyne. The field coils 16, 17, of the dynamo are fed from the supply mains and a separate constant source respectively. The desired characteristic may be produced by means of a variator winding 11 fed by a shunt wound regulator dynamo 10 driven by the metadyne and whose critical excitation build-up speed is equal to the fixed speed desired. Alternatively the same effect may be produced by a speed-responsive mechanical regulator. A further variator winding 7 connected across the primary brushes as shown, or a separately excited winding, may be used on the secondary axis, and if desired both such windings may be used. If it is desired that the motor shall take a falling current for a rising voltage, a second variator winding connected across the supply is put on the primary axis. Both the .primary and secondary currents may be taken through stator windings acting in their respective axes. Instead of using a plurality of variator windings fed by different sources as shown. these sources may be used to excite field windings on an amplifying metadyne which in turn excites a single winding on the main machine. Diagrams are given showing how the coils .may be disposed on the stator poles, a further amplifying metadyne being used in which several coils are carried on one pole, if desired. In modified forms, the brushes are not disposed in quadrature and the secondary brushes may be suhdivided into two short-circuited pairs. Specfication 449,924 is referred to.