. The Street railway journal . sed position of the oilswitch. Fig 4 illustrates the overload relay which is electricallyconnected to the tripping magnet of the oil switches. It isconstructed on the induction principle. There are twoelectromagnets made of laminated iron, and projecting be-tween the poles of each of these magnets is an aluminumsector carrying the movable element of the contact. Sur-rounding part of each pole of the magnet is a short-cir-cuited turn of copper which produces a lag in the magneticfield passing through this turn and thus produces a shiftingof the field across the fa
. The Street railway journal . sed position of the oilswitch. Fig 4 illustrates the overload relay which is electricallyconnected to the tripping magnet of the oil switches. It isconstructed on the induction principle. There are twoelectromagnets made of laminated iron, and projecting be-tween the poles of each of these magnets is an aluminumsector carrying the movable element of the contact. Sur-rounding part of each pole of the magnet is a short-cir-cuited turn of copper which produces a lag in the magneticfield passing through this turn and thus produces a shiftingof the field across the face of the magnetic poles. Thisshifting field tends so to move the aluminum sector as toclose the movable contacts against the stationary one. Themotion of the sector is opposed by an adjustable weight,by means of which the amount of current necessary to closethe relay contacts may be varied. The mechanisms of thetwo sectors are entirely separate, with the exception thatthe contacts themselves are connected in parallel, so that. the tank istanks them- FIG. 9.—CONTROLLING BENCH BOARD should either one be operated it will energize the trippingcoil of the oil switch and thus open the latter. When usedon a two-phase circuit the relay has one of the movementsconnected to one phase and the other to the other phase,through the medium of two series transformers. Whenused on a three-phase circuit, a series transformer is con-nected in each phase and these three transformers are soconnected to the relays that when an overload in one or allof the main wires exceeds that for which the relay is ad-justed, it will operate and open the switch. The cvcle of operation of an automatic oil switch withall its necessary controlling and indicating devices is asfollows: Referring to diagram, Fig. 3, and assuming theoil switch to be closed, the double-pole knife-switch will beclosed in position B. In this position the oil switch may beopened automatically by the polyphase overload relay, or byhand by
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectstreetr, bookyear1884
