Voltage Drop
Calculate voltage drop on a cable run and check the limit.
Questions
Each answer describes what this tool calculates. The result is a design aid. Verify against the current standard.
What does the voltage drop calculator do?
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, the drop as a percent of the supply voltage, and the longest run that still meets the limit.
What is the voltage drop limit for AS/NZS 3000?
The tool uses 5 percent as the default limit and you can change it. The result is marked as a fail above the limit, with a reference to AS/NZS 3000:2018 Clause 3.6.2. 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.
Which inputs change the voltage drop most?
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.
Why does a three phase result differ from a single phase result?
The tool uses a factor of the square root of three for a three phase circuit. It uses a factor of two for a single phase circuit, because the current flows out and back. The same cable and current therefore give a different drop on each supply type.
Can I share or save a voltage drop result?
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 the calculation under a project name needs an account. New Zealand conditions are the default and Australian tables are not included yet.