Question

An LRT car, 5 km distance from the Tayuman, takes 100 A over a 100 mm hard-drawn copper  trolley wire having a resistance of 0.270 ohms per km. The rail and ground return has a resistance  of 0.06 ohm per km. If the station voltage is 750 V, what is the voltage of the car? 

Answer 1

The combined resistance of the wires is

$$R=\rho_w d+\rho_gd.$$

The voltage drop across the wires:

$$V_d=IR=Id(\rho_w+\rho_g).$$

The voltage of the car:

$$V=V_s-V_d=V_s-Id(\rho_w+\rho_g),\\ V=750-100·5(0.27+0.06)=585\text{ V}.$$