GB677932A - Improvements in or relating to an oscillatory current attenuator - Google Patents

Abstract

677,932. Protective arrangements. GARRETT CORPORATION. March 8, 1950 [March 9, 1949], No. 5841/50. Class 38 (iv). An oscillatory current attenuator network for an electrical device (such as a series motor 10) having at least one power input lead 22, through which lead oscillatory currents tend to flow back toward the power source 17 from an inherent source of oscillatory currents within the device, the network including the power input lead 22 and at least one inductive element of the device (such as a series field winding 11b), the inductive element being positioned between the power input lead 22 and the source of oscillatory currents, for example, the brush 14. The series field winding, 11b, and a capacitor 21 forms a so-called " gamma " filter network and by the provision of a series-connected inductance 23 there is obtained, in effect, an unbalanced " T " filter in which critical impedance matching is unnecessary. The inherent resonant frequency of the gamma network must lie outside the frequency bands to be attenuated. In other embodiments are described bidirectional series motors in which two condensers are used with an inductance in series with each field winding, the inductance preferably being wound on a single toroidal core structure.