. The Bell System technical journal . ed. The operationof the circuit is then as follows: 1. The commercial power supply is connected to the 10-volt windings of the transformers through balanced resistances which are soproportioned that the voltage drop due to the magnetizingcurrent is sufficient to reduce the voltages across the windingsto about 10 volts. 2. The resistances form such a large proportion of the total impedances presented to the incoming circuit that the currents throughthe windings are controlled almost entirely by them and, sincethey are non-inductive, this current has approxi
. The Bell System technical journal . ed. The operationof the circuit is then as follows: 1. The commercial power supply is connected to the 10-volt windings of the transformers through balanced resistances which are soproportioned that the voltage drop due to the magnetizingcurrent is sufficient to reduce the voltages across the windingsto about 10 volts. 2. The resistances form such a large proportion of the total impedances presented to the incoming circuit that the currents throughthe windings are controlled almost entirely by them and, sincethey are non-inductive, this current has approximately the samewave shape as the voltage of the power supply. Therefore,since the magnetizing harmonics cannot appear to any largeextent in the magnetizing current, they appear in the voltageacross the transformers and the voltage wave is, therefore,distorted. 3. The distorted voltage wave on each transformer is stepped up between the 10 and 115 volt windings and is impressed on theline at about 115 volts to neutral. DISTORTED NORMAL. POWER LINE IN EXPOSURE AMr RESISTORS TO REDUCE VOLTAGE TO NEUTRAL TO 10 VOLTS Fig. 10—Arrangement for comparing the inductive influence of balanced voltages of different wave shapes. Figure 11 is an oscillogram showing the normal and distortedwave forms and it will be noted that they have about the same although the distorted wave is much more irregular indicatingthe greater harmonic content. When the switch is thrown from nor-mal to distorted, the noise from the loud speaker increases and its SOiME ASPECTS OF NOISE INDUCTION 487 characteristic sound is changed, indicating the effects of increasing theharmonic content of the voltage wave. ■1P^^»^^ A A A ./:Ct\ A A. .A A ^^.y^ W v/ V v/ \ Fig. 11—Oscillograms of normal and distorted balanced voltages. 11-^—Impressed voltage, U-B—Balanced distorted voltage to neutral. In practice, harmonic voltages and currents may arise not only fromgenerating and transforming equipment but
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