Definition – Voltage drop is defined as the amount of voltage loss that occurs through all or part of a circuit due to impedance.
(Note: – Impedance is the property of material that opposes the flow of current in the circuit. Impedance in the circuit includes resistance, inductance & capacitance).
In other words, same supply voltage will not appear across load as voltage drop occurs in the circuit due to impedance. Impedance is the net effect of resistance, inductance & capacitance offered by circuit.
Supply Voltage (Vs) = Voltage drop in line (Vd) + Voltage across the Load (VL ), or
Vs = Vd + VL
VOLTAGE DROP IN SINGLE & THREE PHASE CIRCUIT –
Voltage drop in the circuit can be measured by following equations –
So, for single phase system – Vd = 2 d l r t
for three phase system- Vd = Г3 dlrt
Where – d = distance of one side of wire in ft, I = Current in the circuit in Amp,
r= resistance of wire /1000 ft t = temperature in deg C