480V Three Phase to Single Phase Amps Calculator

Calculate Input Amps

Enter the equipment's 480V three-phase full-load amps. The calculator estimates transformer kVA, 240V three-phase current on the converter side, and the expected single-phase input current.

Equipment full-load amps 3-phase output amps

Equipment voltage 3-phase side

Single-phase service voltage line input

Transformer/converter allowance recommended 92%

Estimated single-phase input 118 amps This is the estimated current on the 230V single-phase line feeding the phase converter.

Load kVA 24.9 Calculated from output voltage and three-phase load amps.

Suggested transformer 30 kVA Uses a 15% headroom estimate, then rounds up to a common kVA size.

240V 3-phase side 60 amps Approximate transformer primary current feeding 240V three-phase.

Planning breaker range 150 amps Planning number only. Final breaker and wire sizing must be verified for the installation.

How the Power Moves

A 480V setup has two current conversions. The load amps at 480V are lower than the current on the 240V transformer primary, and the single-phase line has to supply the whole system.

480V three-phase loadStart with the equipment nameplate amps at 460V or 480V three-phase.

Step-up transformerThe transformer changes 240V three-phase from the converter into 480V three-phase for the machine.

Rotary phase converterThe converter creates the three-phase supply, but it pulls its input power from the single-phase line.

Single-phase serviceFor 480V loads from 230V single-phase, a quick field estimate is usually close to 4x the 480V three-phase load amps.

Use this calculator for planning and sizing discussions. It does not replace a site review by a qualified electrician, and it does not confirm code compliance for breaker, wire, disconnect, conduit, or utility transformer sizing.

The Formula

The clean way to calculate this is to convert the three-phase load into kVA, then divide that power by the single-phase input voltage. The allowance accounts for normal transformer and converter losses.

Three-phase kVA = 1.732 x output volts x output amps / 1000
Single-phase input amps = kVA x 1000 / single-phase volts / allowance
240V transformer primary amps = kVA x 1000 / 1.732 / 240

Example: 30A at 480V

30A at 480V three-phase is about 24.9 kVA. On 230V single-phase with a 92% allowance, that is about 118A input.

Why it is not 30 amps

The machine may only draw 30A at 480V three-phase, but the phase converter and transformer are fed from lower-voltage single-phase power.

Quick field estimate

For 480V equipment powered from 230V single-phase through a converter and transformer, multiply the 480V three-phase amps by about 4.

Need the Right Converter and Transformer?

Phoenix can size the rotary phase converter, transformer package, breaker range, and wire guidance around your actual equipment list. For compressors, HVAC, pumps, CNC equipment, and multiple motors, starting load matters as much as running amps.

460V and 480V machinery

Use NLT, PLT, NLTA, or PLTA packages when you have 230V single-phase service and need 460V three-phase output.

High-inrush loads

Compressor and HVAC loads should be sized for locked-rotor and starting demand, not just running amperage.

Multiple machines

List every motor that can run at the same time and identify the largest motor that starts while the others are already running.