GB436917A - Improvements relating to dynamo electric direct current machines of the commutator type - Google Patents

Abstract

436,917. Improving commutation in dynamo-electric machines; commutating poles. HILL, E. P., 37, Radstock Road, Stretford, Manchester, and ASSOCIATED ELECTRICAL INDUSTRIES, Ltd., Crown House, Aldwych, London. Sept. 4, 1934, No. 25467. [Class 35] In a directcurrent or like commutator machine with split brushes, an inductive impedance 16, preferably an ironcored choke, is interposed between one portion 14 of the brush and the junction point of the leads from the two portions. The winding 15 of a commutating - pole 3 may be interposed between the same junction point and the other portion 13 of the brush. In a two-pole machine the two inductances may be wound on a common core, the inductances being interposed in the leads of the corresponding portions (leading or trailing) of the two brushes. In a multipole machine the positive brushes are connected to a common lead and a common impedance and the negative brushes to a second common lead and impedance. The core of the impedance may be formed with an adjustable air-gap, to prevent saturation at peak load, and the value of the impedance may be regulated by a saturating winding. Fig. 3 shows an arrangement for this purpose. The core 20 is formed with an air-gap 21 and carries the impedance windings 16, 16<1> of a two-pole machine. It also carries a saturating winding 22 which is connected in circuit with the main field winding 24 and a rheostat 25. The exciting supply 24 is connected with a tapping on the rheostat 25 so that the saturating current is weakened as the main exciting current is strengthened and conversely.