. Popular electricity magazine in plain English. controlling force is a suit-able spiral spring. Thevoltage coil is highly in-ductive and the currentin it lags almost 90 de-grees behind the current_in the line and almost 90degrees behind the cur-rent in coil (C) which isnon-inductive. Thus Fig. 77. Single PhaseInduction Wattmeter Prin-ciple when the magnetic flux is a maximum through (V)it is zero through (C) and vice versa. This pro-duces a shifting magnetic field which induceseddy currents in (D) and tends to make it rotate. It can readily be shown that the torque is pro-portional to the pro
. Popular electricity magazine in plain English. controlling force is a suit-able spiral spring. Thevoltage coil is highly in-ductive and the currentin it lags almost 90 de-grees behind the current_in the line and almost 90degrees behind the cur-rent in coil (C) which isnon-inductive. Thus Fig. 77. Single PhaseInduction Wattmeter Prin-ciple when the magnetic flux is a maximum through (V)it is zero through (C) and vice versa. This pro-duces a shifting magnetic field which induceseddy currents in (D) and tends to make it rotate. It can readily be shown that the torque is pro-portional to the product of current X voltage Xpower factor. A diagrammatic sketch of the windings of theWestinghouse induction wattmeter is shown inFig. 78. The magnetic circuit is similar to that of theinduction ammeter made by the same windings are modi-fied to suit the conditionsof power windings consist oftwo principal coils (VV)and (CC). The coils(VV) are connectedacross the line througha resistance. The coils(CC) are connected in. Fig. 78. Windings ofWestinghouse InductionWattmeter series with the coils (VV) have highinductance and thecoils (CC) very little in-ductance. The flux due to (V) is a maximumwhen the flux due to (C) is almost zero and viceversa, thus producing a rotating magnetic fieldwhich induces eddy currents in the drum (D),tending to produce rotation as explained Wattmeters: The two general typesin common use are the moving-coil-fixed-coiltype, and the induction type. Fig. 79 shows theessential features of the first type. The fixed winding consists of two coils (BB)through which the load current passes. Themoving coil or armature (A) consists of severalcoils of very fine wire connected through a re-
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectelectri, bookyear1912
