. Electrical news and engineering. ctly good-natured contempt for a man whocan give and wont give, and we havent any ob-jection to his knowing it. We dont owe himanything—not even, in these days, politeness. Transfer Relay Protective relays that operate by closing a separatedirect-current tripping circuit which in turn trips the circuitIjreaker, have proved more serviceable than shunt-trip re-lays and have come into very general use. In some cases,however, a separate direct-current tripping circuit is notavailable and other means must be sought. The use oftransfer relays is the best solution s
. Electrical news and engineering. ctly good-natured contempt for a man whocan give and wont give, and we havent any ob-jection to his knowing it. We dont owe himanything—not even, in these days, politeness. Transfer Relay Protective relays that operate by closing a separatedirect-current tripping circuit which in turn trips the circuitIjreaker, have proved more serviceable than shunt-trip re-lays and have come into very general use. In some cases,however, a separate direct-current tripping circuit is notavailable and other means must be sought. The use oftransfer relays is the best solution so far obtained, for theyenergize the trip coil off the circuit-breaker through currenttransformers. While designed particularly for use with theWestinghouse types CO and CR relays, the type BT relaycan be applied to any make of circuit-closing relay of similarcharacteristics. The breaker operates solely through thecurrent transformer and the relays. When there is nofault on the line, the trip coil of tlie breaker is mechanically. rripCoil -Or. Note- fill Conncclions ihoivn as v,emd from Dear of Apparctos and electrically isolated from the circuit, avoiding possibilityof tripping due to imperfection in the relay contacts ordi-narily shunting the trip coil. The relay contains two seriescoils, an upper or operating coil and a lower or holding coil(see diagram of connections). The holding coil holds downthe armature core, until a third coil, wound on the samemagnetic circuit and known as the releasing coil, is short-circuited by the protective relay. The releasing coil acts asthe secondary of a transformer and when short-circuited acurrent flows through it, demagnetising the core. The hold-ing coil, therefore, allows the operating coil to raise the corewhich operates the transfer switch, thus closing the trip coilcircuit. The transfer switch and otlier current carryingparts of the relay are designed to carry 5 amperes contin- uously. l)Ut during times of short circuit the switch
Size: 2058px × 1215px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bo, bookcentury1800, bookdecade1890, bookidelectricalnewsen27donm
