What is potential drop? how it is calculated? piease explain with example........
In situations where the circuit conductors span large distances, it is necessary to calculate the voltage drop in order to determine if the circuit's voltage will be maintained over the long distance. If the voltage drop is too great, the circuit conductor must be increased (up-sized) in order to maintain the current between the points. The calculations for a single-phase circuit and a three-phase circuit differ slightly. Listed below are the voltage drop calculations for the two:
Single-phase voltage drop calculation:
Three-phase voltage drop calculation:
VD = Voltage drop (conductor temp of 75°C) in volts
VD% = Percentage of voltage drop (VD ÷ source voltage x 100). It is this value that is commonly called "voltage drop" and is cited in the NEC 215.2(A)(4) and throughout the NEC.
L = One-way length of the circuit's feeder (in feet)
R = Resistance factor per NEC Chapter 9, Table 8, in ohm/ft
I = Load current (in amperes)
Source voltage = The voltage of the branch circuit at the source of power. Typically the source voltage is either 120, 208, 240, 277, or 480 V.