How do you get 240 3 phase volts from 480 3 phase volts?

Answer 1

480 volts 3 phase is not a household service in any country and cannot be dealt-with as a DIY project.

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As always, if you are in doubt about what to do, the best advice anyone should give you is to call a licensed electrician to advise what work is needed.

Before you do any work yourself,

on electrical circuits, equipment or appliances,

always use a test meter to ensure the circuit is, in fact, de-energized.

IF YOU ARE NOT ALREADY SURE YOU CAN DO THIS JOB

SAFELY AND COMPETENTLY

REFER THIS WORK TO QUALIFIED PROFESSIONALS.

Answer

You cannot obtain 240 V from a 480-V three-phase supply, if you are describing a three-phase, four-wire, system. If 240 V is a phase voltage, then the corresponding line voltage must be 415 V. If 480 V is a line voltage, then the corresponding phase voltage must be 277 V.

Answer 2

Long Answer:

Are you sure you have three phase 240v power? If it has three WIRES (black, white, red) that's not the same as three phase power.

A good rule of thumb is if the power is part of a residential distribution system (in your home), it's something called 'split single phase'. If it's part of a commercial distro system (in a commercial or industrial area) it is likely three phase, which actually uses four wires in most cases (black/red/blue/white or brown/orange/yellow/gray, depending on the voltage).

If you have 240v split single phase (which I suspect) you would need a transformer to get the voltage up to 480v, and a phase converter (Google it) to 'create' the three phase power.

There's too many variables for me to give a definitive answer without seeing the installation.

Short Answer:

This translates to: Call a (real) electrician. They will be able to verify exactly what the supply voltage and phase is, and they will let you know if it's actually doable or just a waste of time. It won't cost very much just for them to give you this advice.