GB391793A - Improvements in and relating to protective devices for alternating current dynamo-electric machines - Google Patents

Abstract

391,793. Protective cut-out arrangements. INTERNATIONAL GENERAL ELECTRIC CO., Inc., 120, Broadway, New York, U.S.A.-(Assignees of Allgemeine Elektricitõts-Ges.; 2, Friedrich Karl-Ufer, Berlin.) Oct. 26, 1931, No. 29673. Convention date, Oct. 25, 1930. [Class 38 (v).] For the protection of an alternator, a relay W<1> is used having a winding s<1> energized from a current transformer d<1> associated with the A.C. winding A, and a winding p<1> connected between the midpoint c of the field winding E, or of an auxiliary winding on the field system, and the mid-point e of a resistance shunting that winding. The primary of the transformer d<1> is energized from two parallel sections of a phase, so that the effect of working-frequency currents in the two halves is neutralized, but harmonics due to mechanical asymmetry in the winding A are able to flow and energize the coil s<1>. When a fault arises, currents of the same frequency are no longer neutralized in the winding p<1>, which accordingly operates the relay. A similar arrangement W<2>, d<2> may be provided for another phase of the winding A, the windings p<1> being connected in series (as shown) or in parallel, or the secondaries of the transformers can be connected 'in series and energize the winding s<1> of a single relay, Fig. 3 (not shown). If the alternator has no parallel sections, an auxiliary winding is provided to embrace one or several of, but not all, the pole-pairs. An auxiliary winding could: also replace the current-transformers in the case of parallel-section windings.