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Voltage Drop of TwoWire and ThreeWire SystemsAuthor: E.E. Kimberly In the twowire line in Example 34, there is a voltage drop equal to
In order that 230 volts may be available at the load, the generator voltage must be raised to 230 + 20 = 250 volts. The difference between the sendingend (generator) voltage and the receivingend (load) voltage is called the line voltage drop. If, in a threewire circuit, the load is not equally divided between the two parts of the circuit, the voltages across the two parts at the load will not be equal. This inequality is caused by resistance in the middle wire. Example 37.  A constantvoltage double generator set supplies 'power over a threewire line with a resistance of 0.5 ohm per wire to unbalancedload resistance units of 20 ohms and 30 ohms, as in Fig. 37. Calculate the currents in all three lines and the voltage appearing at each section of load. Solution.  The load resistor of lesser value will have a greater current. Hence, I_{m} will be in the direction shown, and The sum of all voltage drops in a series circuit is equal to the applied voltage. In this case, the voltages applied to the top and bottom parts of the circuit are 125 volts. Therefore, by Kirchhoff's voltage laws, the equations are:
It having been established that I_{m} is flowing toward the left, the I_{m}R_{m} drop is from right to left as indicated. Hence, in traversing the lower circuit in the direction of I_{b}, the established I_{m}R_{m} drop is taken as negative. Since I_{m} = I_{a}  I_{b},
By simultaneous solution I_{b} = 4.12 amp and I_{a} = 6.05 amp. Then, I_{m} = I_{a}  I_{b} = 1.93 amp. Also,


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