. The Bell System technical journal . a condition similar toFig. 15-C) the noise in the loud speaker is much lower than whena metallic connection is used and thus indicates a substantialreduction in the The demonstration setup is so arranged that the single-phase portioncan be transposed. With the single-phase portion metallically. connected to the three-phase portion, transposing the single-phase portion causes relatively little change in the noise fromthe loud speaker. However, when the single-phase portion isisolated from the three-phase portion by the transformer,transposing i
. The Bell System technical journal . a condition similar toFig. 15-C) the noise in the loud speaker is much lower than whena metallic connection is used and thus indicates a substantialreduction in the The demonstration setup is so arranged that the single-phase portioncan be transposed. With the single-phase portion metallically. connected to the three-phase portion, transposing the single-phase portion causes relatively little change in the noise fromthe loud speaker. However, when the single-phase portion isisolated from the three-phase portion by the transformer,transposing it further reduces the noise materially. When thesingle-phase portion is connected metallically to the three-phaseportion, the induction is largely due to residual voltage and assuch is not affected by the power circuit transpositions. Whenit is connected through the isolating transformer, however, thereis no residual voltage present and the induction, being due tobalanced voltages, is materially reduced by the power TELEPHONE LINE TOAMPLIFIER Fig. 16—Influence of single-phase extension to three-phase power line. Three-phase portion . As far as the three-phase portion of the line is concerned, the single-phase extension acts as additional admittance to ground on twoof the wires. Consequently if the single-phase extension is long, 492 BELL SYSTEM TECHNICAL JOURNAL the admittance unbalances between the various wires andground may be fairly large. 2. In considering the effects of the admittance unbalances, there are two conditions which must be considered; where the trans-formers supplying the three-phase portion are Y groundedon the line side, and where they are delta on the line the supply transformers are connected delta on the lineside, there is no path for residual current into the transformersand the voltages of the conductors to earth adjust themselvesso that the net charging current to earth is zero (although therewill be some interchange of ch
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Keywords: ., bookcentury1900, bookdecade1920, booksubjecttechnology, bookyear1
