# Is there a device to use 3-phase 400 V and convert into 230 V 1-phase?

I only know basics about electrical power and basically don't know anything about converters/inverters/transformers.

My situation is: I have an EV that I can charge only using 1 phase, up to 6.6 kW. My charger is capable of 32 A, which is somewhere in the 7.2 kW range. But my house has 25 A fuses on 3 phases. So, I can charge at the 24 A setting if one phase is completely clear of other consumers.

My question is: Can I spread the amperage over 3 phases to create 1 phase with a higher amperage?

Like, for example, I would be putting 10 A load on three phases on the 3-phase side and using 30 A load on the single phase side (that is not the calculation, just an example of the situation I want).

• Perhaps a Zig-Zag transformer? Commented Feb 19, 2022 at 8:26
• Use a 3 phase electric motor to drive a single phase generator, basically power in = power out + losses. Commented Feb 19, 2022 at 10:04
• Can your charger accept delta connection (380 V input)? If yes, your current would be sqrt(3) times lower. If not, three to single phase inverters does exist but are expensive. A 380-220 transformer would be an option too. Commented Feb 19, 2022 at 11:56
• Will be easier replace wiring with bigger size and set new or replace breaker. That kind of devices, you seeking, may be expensive. Commented Feb 19, 2022 at 12:32
• The voltage has been changed many years ago, it is 400 and 230 V now.
– Uwe
Commented Feb 19, 2022 at 18:39

## 3 Answers

The optimal solution would be another charger designed for 3 phase input.

It is possible to convert three phases with 230 V 12 A each to a single phase 230 V 36 A. Two heavy, large and expensive transformers are needed.

A transformer for 230 to 76.67 V and 2.76 kW, another for 400 to 153.33 V rated for 5.52 kW. The 76.67 and 153.33 V secondary windings are connected in series to get 230 V 30 A 8.28 kW. The first transformer primary winding is connected to phase L1 and neutral N, the second transformer primary to L2 and L3.

The voltages L1 to N and from L2 to L3 are in phase. The two secondary windings should be connected in the proper order to add both voltages and get 230 V.

There are things to think about. Not convenient. You could get a 380 to 220 mains transformer rated at more than say 8KVA, heavy and not cheap. You could rewire your house switchboard so one incoming phase supplies the EV charger and nothing else. The remaining 2 phases supply the rest of the house. If your house does not have any 3-phase motors this should be doable.

Home electric car chargers are fancy power switches, all the charging electronics is in the car itself. converting 380V three phase into single phase will almost certainly cost more than getting the correct 3 phase charger.

• True for this question but important not to take the " just a switch" thing too far. Good charge points have sophisticated electronics in them to detect dangerous earth faults, particularly in TN-C-S earthing systems, ie PEN loss. Increasingly we're seeing cheap chargers without the required features, hand-waved away as the responsibility of the supply and installer, and that trend is literally going to kill someone. So it's just a switch if it's a bad charger, sure. Nothing in them can help the OP though.
– Dan
Commented Feb 20, 2022 at 14:34