What Is Voltage Drop
Voltage drop is the loss of voltage that occurs as current travels through a conductor's resistance. Every real conductor has some resistance, so every circuit experiences some voltage drop.
What causes voltage drop
As current flows through a conductor, the conductor's resistance consumes some of the supply voltage. The longer or thinner the conductor, the higher its resistance, and the greater the voltage drop for a given current.
Why it matters
Excessive voltage drop means equipment at the end of a circuit receives less voltage than intended, which can reduce performance, cause overheating in motors, or trip sensitive electronics. Keeping voltage drop within a target percentage of source voltage is standard practice.
Single-phase vs. three-phase
Single-phase voltage drop accounts for the round-trip path through both conductors, so the calculation includes a factor of 2. Three-phase voltage drop instead uses a factor of √3, reflecting the phase relationship between the three conductors.