GB221551A - Improvements in electric converting apparatus - Google Patents

Abstract

221,551. Calverley, J. E., and Highfield, W. E. June 7, 1923. Commutator switching - arrangements. - In apparatus for converting direct current from a system 4 at one voltage to a system 6 at another voltage by means of polyphase transformers having three sets of windings, two of which, 3, 5, are respectively connected to two groups of commutating gear 16, 13, rotated by a synchronous motor 11, as described in Specification 150,825, the third set of windings 20 is connected to the motor and supplies the power for driving the motor, white the magnetizing current for the polyphase transformers is chiefly supplied to the third set of windings by the motor, a separate source of polyphase current for driving the motor and supplying exciting current to the third winding being thus rendered unnecessary. The field' current of the synchronous motor is supplied from an exciting dynamo 12 and is regulated by adjusting a series resistance 24 or by varying the current in the field winding 23 of the dynamo 12 by means of a rheostat 22. The speed of the motor may be maintained constant with increasing load by adjusting the field excitation, as described in Specification 221,550. Automatic regulation may be obtained by means of an additional field winding on the rotor of the synchronous motor 11, this winding being placed in series with the direct-current mains 6 or connected' across a resistance inserted in these mains. The exciting dynamo way be run as a motor, from a battery 28, or from one of the direct-current systems, for the purpose of starting the apparatus.