3-phase 380 V to 3-phase 230 V

Question

I have a portable bearing heater which works with 3-phase 230 V power supply.

My power supply is 3-phase 380 V. Is there any way to convert the 3-phase 380 V to 3-phase 230 V? Please note that since the equipment is portable, it is important that the solution be portable too.

I added the picture of wiring diagram of the equipment. The manual indicates: The equipment is designed for 3 phase 230V power supply (Between each hot wire, 220 volts can be measured) when 2 phases are connected. it means 2 phases out of 3 phases are connected.

The supply power is 3-phase 380V,which means between each hot wire, 380 volts can be measured and between the neutral and any of hot wires, 220 volts can be measured

Answer 1

Figure 1. Coloured up version for single-phase 230 V + N wiring.

It appears from the wiring diagram that you can just connect L3 to neutral instead with no internal modification.

The only concern should be that the components' insulation now has to withstand 230 V instead of \$ \frac {230}{\sqrt 3} \ \text V\$. You should check, if possible, that they are rated for that.

Answer 2

Most likely your heater expects supply of three phases at 230 V(rms) phase-to-neutral, and the supply you have is three phases at 380 V(rms) phase-to-phase.

Fortunately these are the same* thing! So most likely you won't need any conversion, except perhaps a plug adapter.

(*: Within a few percent that can be chalked up to rounding; and utilities seemingly redefining their nominal voltage by 10 V up or down every several decades without non-electricians in the populance noticing; and is dwarfed by tolerances anyway).

It is quite rare and nonstandard to find three-phase AC at 230 V measured phase-to-phase or 380 V measured phase-to-neutral, so it would require extraordinary evidence to believe your heater or supply is one of those.

Answer 3

There may be a simple solution to this depending on the connection, If the load is connected between the two phases and no neutral connection as you have indicated in the comments section, you can connect the bearing heater between L1 and the neutral from your 380v supply. This will give you a voltage of approximately 220v and de-rate the output power by about 1KVA. The only other option without knowing the internal connections would be a big transformer on a trolley.

Looking at your wiring diagram it appears that what I suggested above will work. The only problem that I can see is if the 230v neutral wire is used by any monitoring electronics not shown on the diagram.

^{simulate this circuit – Schematic created using CircuitLab}

The best way to do this would be a 3 wire connection as shown above by replacing the existing plug with a 380v one, or if you need to keep the 230v compatibility an adaptor box that is clearly marked for use with only this unit.

Answer 4

^{simulate this circuit – Schematic created using CircuitLab}

You have only to rewire heating elements from wye to delta connection.

EDIT:

You said:

Actually the equipment use 2 phases out of 3-phase 230

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All you have to do is to connect your load between phase to neutral, and not phase to phase anymore. But 22kVA seems huge power for single phase operation. You'd better dismount your device and post some pictures. For exaple you could separate the electronic part which needs low voltage by means of SMPS or transformer and the power part by replacing two phase graetz diode bridge with 3 phase diode bridge.

Check if L1, L2 and L3 are series connected as shown in schematics. There is a notation: 3x6mm^2 or 3x10mm^2 at 2x220V, which means that sections are made for different voltage, combining them series or parallel.

You have to use phase to neutral voltage for control unit. This can be easily done by rewiring L3 control supply to N.

The next thing is to check if the coils are really connected in series. IMO, by combining L2 and L3 in series or parallel you can get 380V/220V. So they shold be connected parallel right now.

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Another possibility for combining multiple voltages. Watch if the windings are wound in same direction or they are connected anti series, dectructing their magnetic field.

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