Conversion from 3-phase AC to 1-phase AC higher current - Page 1
Forum section: electronics / general

author: marekm
author_rank: Contributor
timestamp: September 16, 2025, 07:41:19 pm
content: I'm looking for a way to charge an EV at home just a little faster. The EV has a Type 2 connector but only accepts 1-phase 230V AC, up to 6.6 kW which requires a 32A circuit. Home wiring is only good up to 16A but it is 3-phase, typical charging cables will only use 1 phase at 1/3 the power (same as the "granny charger" that plugs into a standard 230V AC socket and is limited to 2.3kW).Simplest solution could be to use a 400V/230V transformer from 2 phases, 6kW at 15A from each phase is just barely enough, still not balanced (no load on the third phase) and a copper/iron transformer of this power is quite expensive. There are Vv (open delta) and Scott-T transformers, still heavy and expensive and not balanced.It could be done with a 3-phase PFC rectifier that makes a +/-350V DC bus and then IGBT half-bridge with LC filter makes 230V AC with the common neutral from input to output. I've seen something similar (only 1-phase AC input, and separate DC/DC converter from battery to the DC bus used during power outages) in on-line UPS devices.Is such a thing (even included in an EV charger) already made and available at reasonable cost? Search results I could find are mostly about the opposite conversion (inverters powered from 1-phase mains to drive 3-phase motors).

author: synccond
author_rank: Contributor
timestamp: September 17, 2025, 07:40:49 pm
content: Not very common. The only 3-to-single phase converter I have seen in production form is for use in induction heating or arc furnaces. These typically require a few thousand amps at low voltage.Most (if not all) three phase EV chargers will simply go straight rectifier to DC, then DC/DC converter to drive the batteries directly. Why bother going to single phase.

author: nightfire
author_rank: Frequent Contributor
timestamp: September 17, 2025, 08:57:02 pm
content: The Type-2 cable usually has a resistor wired into to announce to the charger/wallbox the potential amperage they are good for.So theoretically there should be the possibility that you use such a cable to limit the power drawn to some safe margin below 16A.Page here in german, but i think you get the idea:https://www.goingelectric.de/wiki/Typ2-Signalisierung-und-Steckercodierung/So 13A limit is possible with canonical measures...So you could use a standard CEE 3 phase plug-to-type2 converter or mobile wallbox, and use a type2 cable that is wired to 13A.(AT least theoretically)

author: Siwastaja
author_rank: Super Contributor
timestamp: September 18, 2025, 06:08:16 am
content: Just go the 400/240V autotransformer route, it's the only simple and cheap solution, and there are existing products. You double from 1/3 to 2/3 utilization of your contract that way, last 1/3 would be diminishing returns.Low-current 3-phase supplies are PITA anyway, so just do what you need to do anyway, balance your 1-phase loads by rewiring into different phases.I have 3x25A contract, and charge Nissan Leaf from one phase at 20A, simply moved most of the stuff out to other two phases. Can totally see myself upping that charging to 1x25A and move remaining stuff out of that phase, but I'm happy with 1x20A.

author: Jeroen3
author_rank: Super Contributor
timestamp: September 18, 2025, 06:54:34 am
content: Quote from: marekm on September 16, 2025, 07:41:19 pmYes this exists, they call it a DC charger. They take 3 phase 400V, rectify it and put put in on the large DC pins.It will be more expensive than a simple AC EV Socket, because it replaces the cars built-in charger.These products often also allow V2G capabilities.

author: Siwastaja
author_rank: Super Contributor
timestamp: September 18, 2025, 07:12:17 am
content: Quote from: Jeroen3 on September 18, 2025, 06:54:34 amThis. Power conversion 3-ph -> internal DC -> 1-ph AC -> car DC makes absolutely zero sense. Just do 3ph -> car DC, if you need to - aka DC charger (CCS or Chademo).

author: Jeroen3
author_rank: Super Contributor
timestamp: September 18, 2025, 07:40:04 am
content: Besides, if the car only takes 1 phase it is probably a plug-in hybrid and fast chargingat homeis completely unnecessary due to the small battery, and of course the lack of range anxiety because you can charge 700km+ in 3 minutes using a hose.

author: Siwastaja
author_rank: Super Contributor
timestamp: September 18, 2025, 09:03:36 am
content: Quote from: Jeroen3 on September 18, 2025, 07:40:04 am"6.6kW 1-phase" sounds like Nissan Leaf. The 62kWh model is, range-wise, a real EV, so I understand the desire for faster home charging e.g. if coming home very late at night with empty battery and having to leave early in the morning. Putting 50kWh in using 1x16A takes whopping 14 hours.

author: marekm
author_rank: Contributor
timestamp: September 18, 2025, 02:02:43 pm
content: It's a new Leapmotor T03. It does support fast DC charging too (large 2 pins below the Type 2 connector), but the DC chargers I've seen so far are high power and very expensive. Are there any reasonably priced DC chargers in the 11kW range?Crazy idea - use a small 1-phase on-grid PV inverter to add extra current to one phase, and power the DC side of the inverter from two AC/DC power supplies powered from the other 2 phases. I happen to have such a spare 1-phase inverter (Growatt MIN 3000-TL-XE) after my initially small on-grid PV setup was upgraded (more panels, 3-phase inverter) and a bunch of old Emerson/Ericsson 54V 6A telecom power supplies (intended for battery charging so should have no problem working at the current limit), each three in series could work as one ~1kW PV string, two such strings powered from two other phases.

author: Siwastaja
author_rank: Super Contributor
timestamp: September 18, 2025, 06:14:24 pm
content: With any crazy idea involving PV inverters, just remember they are not isolated! Very careful with that because it's easy to forget even if you "know" that.It would make more sense to build a DC EV charger from a battery hybrid inverter - they are crazy cheap nowadays: then you can also add PV panels to it if you so wish. Basically just HVDC contactors, safety logic and data conversion between CCS <-> whatever BMS format supported by the hybrid inverter. But itissome serious work, but your crazy alternatives seem quite complicated too.

author: marekm
author_rank: Contributor
timestamp: September 18, 2025, 08:27:50 pm
content: Yes I know, and wouldn't recommend building this to anyone else - I just happen to have all the parts, would make sure all accessible metal parts are properly earthed, and I also have a type B (detecting DC leakage) RCD. The inverter would be set up for "zero export" with a CT on the incoming phase, so it can only add as much power as is drawn from it while charging.Perhaps someone already makes reasonably priced 7-11kW DC EV chargers but I just haven't found them yet, only very high power and very high prices. I suspect most of the world don't have 3-phase power at home so EV makers don't care much. Any pointers to such a thing are welcome, searches find lots of results but most of them aren't what I'm looking for.Can the 400V to 230V transformer be an auto-transformer? It would be smaller and cheaper (by about half) but not isolated, does the onboard charger care if the "neutral" is not really neutral but at a voltage close to the middle between two phases? I guess it should be fine if it also supports US-style 240V split-phase mains, but European version could have some extra safety checks preventing charging. Easiest to find would be a 230V/230V 4kVA isolation transformer wired as 460V/230V auto-transformer, but will the car still charge from 200V (30A, 6kW) or is that too low? (official mains voltage here is 230V +/- 10% = 207V to 253V)Battery hybrid inverter could actually be used in a much simpler way - Deye has the "grid peak shaving" feature where battery power is added to grid power, but it would need a large battery (about 2/3 of EV battery kWh) - or parallel external charger powered from the other 2 phases, "infinite battery" (tm). Certainly worth looking into, as I plan to have such a hybrid anyway (with more PV panels).

author: Marco
author_rank: Super Contributor
timestamp: September 18, 2025, 09:37:32 pm
content: Sigen has a DC charger module for their home battery system, 6k Euros for inverter and DC charger ... and no battery yet.

author: marekm
author_rank: Contributor
timestamp: September 18, 2025, 11:08:22 pm
content: Ouch. I mean a self-contained DC charger (not part of a larger system), with a red 3-phase 5-pin 400V AC plug at the input, and CCS Combo 2 connector at the ootput. It is unknown whether the T03 also supports slower DC charging over the Type 2 connector alone (DC-low/DC-mid, without the two big DC-high pins), all I know for now is they claim 48kW DC fast charge from 30% to 80% in 36 minutes. I've read the DC charging communication protocol is much more complex, not a simple PWM anymore so probably not easy to DIY.

author: Marco
author_rank: Super Contributor
timestamp: September 19, 2025, 12:54:39 pm
content: You'd think there would be plenty of mobile DC chargers with industrial 3 phase plugs and CCS2, but I only see Chinese imports and ridiculously expensive stuff.

author: NiHaoMike
author_rank: Super Contributor
timestamp: September 20, 2025, 11:55:17 am
content: Maybe a surplus 3 phase motor (Y wired) and an autotransformer on one phase to lower it slightly so that it pushes power out on that phase? That's usually undesirable as it causes the motor to heat up more, but probably would be fine with the motor left unloaded just like it would be when using a motor as a phase converter.

author: Jeroen3
author_rank: Super Contributor
timestamp: September 21, 2025, 02:02:47 pm
content: If you're going to bodge your own 3-1 phase converter you'd be better off just getting the DC charger imho.I think your options are:- buy an oversized scott-t transfromer and accept the losses of transformers. (the car is a non-linear load due to rectifiers)- buy a DC charger, they are mostly intended for industrial use though, so they are priced like that.- get a home battery with either the dc charge option (eg: haier) or peak shaving option to allow 25/32A single phase operation (eg: victron)- upgrade your electrical connection- buy a real car, you usage may be exceeding the target audience of this small city car.

author: mzzj
author_rank: Super Contributor
timestamp: September 21, 2025, 08:17:46 pm
content: Quote from: marekm on September 18, 2025, 08:27:50 pmKinda other way around. Most EV makers have 11kW 3-phase onboard charger on euro models.Market for "low" power 3-phase DC chargers would be pretty narrow since this is pretty much Nissan-specific problem.

author: fastbike
author_rank: Regular Contributor
timestamp: October 10, 2025, 05:17:16 am
content: Or upgrade the on board charger.Dala is looking at a project to do this for very old Leaf, I think he will use a Tesla charger.