Estimate voltage drop, percent drop, and voltage at the load for a copper conductor run.
Voltage drop is the loss along a conductor due to its resistance. For single-phase, Vdrop = 2 × L × I × R / 1000; for three-phase, Vdrop = 1.732 × L × I × R / 1000, where L is the one-way length in feet, I is current in amps, and R is the conductor resistance in ohms per 1000 ft.
Excessive drop starves motors of torque, dims lighting, and upsets sensitive loads like drives and instrumentation. The NEC recommends keeping branch-circuit drop under 3% and total under 5%. For panel layout and conductor practices, see the control panel design guide.
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