Voltage drop calculator

The tool reads the resistance and reactance of the conductor. It combines them at the power factor to get the drop in millivolts per amp metre. It then reports the drop in volts and the longest run that still meets the limit. It also gives the drop as a percent of the supply voltage.

The default limit is 5 percent and you can change it. Choosing extra-low voltage sets the limit to 10 percent from AS/NZS 3000:2018 Clause 7.5.7. A result above the limit is marked as a fail and a warning appears above 80 percent of the limit. Impedance comes from AS/NZS 3008.1.2:2017 Table 30 and Tables 34 to 35.

Design current and run length scale the drop directly. Conductor size, material and insulation set the resistance and reactance. Power factor sets how much reactance adds to the drop. Cables in parallel divide both resistance and reactance by the number of cables.

The tool multiplies by the square root of three for a three phase result. It multiplies by two for a single phase result, because the current flows out and back. The same cable and current therefore give a different drop on each supply type.

Yes. The phases, voltage, current, length, power factor, cable and limit all sit in the page address. Copy the link to send the same calculation to somebody else. Saving under a project name needs an account. In the Standard select, pick AS/NZS 3008.1.2 for New Zealand or AS/NZS 3008.1.1 for Australia, both 2017 editions.