Three phase

Can someone point in the direction for a 3 phase inverter for up to 480V feeding off 48V battery. I got plenty of solar to feed it, reason is I noticed most 3 phase tools are cheaper to get i.e. welders, compressors etc, more efficient of course and can handle larger projects.

Boom. You now know as much about it as I do

Edit, sorry, not battery feed but direct solar feed.

DThames said:

Boom. You now know as much about it as I do

Edit, sorry, not battery feed but direct solar feed.

Click to expand...

I can feed it directly from solar array, though it would suck if a cloud passed over while welding and the voltage drops below 500V to shut everything down or can't run tools on cloudy day.

Three of these would make 120/208Y. You could add a 3-phase transformer for 480V.


SMA has much larger stuff for the US market, also intermediate size (75kW) for European market.

How many watts or horsepower? VFD is another way to go, but only lower horsepower ones indicate single-phase input is acceptable.
I've imagined PV going to the high voltage rail of a VFD (with single-phase AC also rectified to feed it when the sun hides.) 400V battery would be a better setup.

Hedges said:

Three of these would make 120/208Y. You could add a 3-phase transformer for 480V.

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SMA has much larger stuff for the US market, also intermediate size (75kW) for European market.

How many watts or horsepower? VFD is another way to go, but only lower horsepower ones indicate single-phase input is acceptable.
I've imagined PV going to the high voltage rail of a VFD (with single-phase AC also rectified to feed it when the sun hides.) 400V battery would be a better setup.

Click to expand...

Looking at around 5 horsepower for compressor and around 460V 24A 11,040W. A 400V battery setup lol that would be quite the sight to see, I'm going to see if I can see what that looks like.

Weldman said:

Looking at around 5 horsepower for compressor and around 460V 24A 11,040W. A 400V battery setup lol that would be quite the sight to see, I'm going to see if I can see what that looks like.

Click to expand...

Some 3 phase motors are 208-230/460 dual voltage. They have 9 leads, which can be connected for high or for low voltage. So 3, 120v inverters without a step up transformer might be a solution, if your motors would run okay on 208v. With the current energy efficiency laws 208-230v range on motor ratings might be a thing of the past, as you can't get best efficiency at both 208 and at 230.

Rather run the 460V so we have about 600V in solar coming in being converted into a 400V battery as @Hedges pointed out and going back to 460V so we aren't losing so much in all the voltage swings. Seen a BMW i3 has battery voltage that is needed.

Do you need new charge controller(s) as well or just 3 phase inverter?

rhino said:

Do you need new charge controller(s) as well or just 3 phase inverter?

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Yes I do as I have yet to plug in all these panels or even weld a mount for them yet. One day at a time...

Weldman said:

Looking at around 5 horsepower for compressor and around 460V 24A 11,040W. A 400V battery setup lol that would be quite the sight to see, I'm going to see if I can see what that looks like.

Click to expand...

11kW is just about the continuous capability of two SI-6048, assuming 25 degree C temperature. With 3 connected for 3-phase, would be good.
But a 11kW motor likely draws 50kW on startup. SI-6048 spec says 11kW surge for 3 seconds. Even four wired 2s2p like I have would be 44kW, which might or might not be sufficient.

If you use a VFD, that can start a motor without drawing surge current.
A compressor has an unloader, but once it starts turning pressure builds back up. The VFD I have on a pump is programmed to ramp up very slowly. You would want to ramp up faster so motor is at full speed before pressure builds. Or, arrange for unloading to continue until it is at speed.

A lot of battery, yes. My $5000 AGM battery bank would run that motor for about an hour or so.
If you have PV coming in, that will keep it going after battery has started the motor. 11 kW from PV is not unreasonable. A single orientation of panels would only peak at that mid-day. A 20 kW (STC) array arranged as two 10 kW arrays oriented for morning and afternoon sun could sustain 11 kW for many hours.

There are other ways to run 3-phase motors, including rotary converters. I had a motor-generator welder with 3-phase motor. I hooked 24V batteries to the welding terminals to get it spinning, then connected 240VAC single (split) phase to two of the AC wires and it ran.

Here's a European model inverter that would do what you want.
60 kW. But it needs battery 575V to 1000V.


Smaller pulley on the compressor motor, maybe smaller motor as well. Do you really need the full CFM it is rated for?

Did I misunderstand - are people recommending using three separate single phase inverters to create a three phase feed? If so, how do you get them to sync so the outputs are synchronous three phase, rather than the phase timing being all over the place?

There are 3-phase inverters. There are also single-phase inverters which use a data cable to synchronize them.
My avatar picture shows four SI-6048 wired 2s2p; data cables synchronize these 120V inverters to produce 120/240V split phase. They can also be wired and configured for 120/208Y.

That's the battery inverters. AC coupled PV inverters are sometimes 3-phase, other times single phase and don't have to know about other phases, just the 240V or 208V they are feeding.

Sounds like unless one is making money from said tools I listed to use on 3 phase it's better to just crank a 3 phase genset up as it's needed or put a gas/diesel engine on the compressor.

VFD may be a good option. I don't know how good the no-name ones are. I have a Hitachi VFD for 2 HP, which accepts single-phase input, but their larger models specified 3-phase only. I do see some in the 5 HP range which indicate single-phase input, and are cheap enough.


I think the poor power factor of my VFD upset a transformerless GT PV inverter, but it didn't seem to be a problem for the transformer-type Sunny Island battery inverter.

Batteryhookup.com - first inverter in a search is a 25kw three phase inverter for about $900. 60 hz for North American use. Needs 500 to 1000 volts worth of batteries.

BEWARE........most commercial three phase is delta hi-leg and IS NOT COMPATABLE with single phase inverters. Residential type inverters can only be used on 120/208 three phase at a reduced capacity......they will feed in at 120 volts not at 240 volts, there is no common neutral in delta hi-leg......it’s not balanced.....A phase to B phase is balanced but the A to C phase and B to C phase are not balanced, the neutral is around the corner between A phase and B phase and +- 60 volts and +-60 degrees out of phase. this WILL DESTROY INVERTERS . 480 volt three phase is WYE connected BUT the inverters will be looking into 277 volts.....not 480 volts........THIS IS NOT AN AREA FOR BEGINEERS.....HIRE A PROPER ENGINEER FOR THIS PART! I have had to clean up too many messes made by persons trying this. There is a very good reason that commercial inverters are so expensive. Even Schneider won’t go there......

Here's a chart of popular 3-phase configurations, and which (SMA) single-phase and 3-phase inverters can be used.

Weldman said:

Can someone point in the direction for a 3 phase inverter for up to 480V feeding off 48V battery. I got plenty of solar to feed it, reason is I noticed most 3 phase tools are cheaper to get i.e. welders, compressors etc, more efficient of course and can handle larger projects.

Click to expand...

look at deye 12kw , they have a full 3 phase, but it is european standards 3 phase

Weldman said:

Looking at around 5 horsepower for compressor and around 460V 24A 11,040W. A 400V battery setup lol that would be quite the sight to see, I'm going to see if I can see what that looks like.

Click to expand...

Not to be picky, But 5hp 460-480v would be 7.5amps at 3-phase 60hz

I must of mixed the single phase up with the three phase.

@Hedges,

thanks for posting that , I will stick that in my reference library. I do commercial electric and will find that handy. I convert Austrian automated woodworking machinery from their three phase to our three phase. I have seen legacy systems with corner grounded and delta ungrounded systems that date back into the ‘30’s, Farmers will not upgrade to more modern wiring if their ‘30’s 100 h.p. Pump is still working or can be rebuilt. PG &E will not hook up such a system but if it exists it is grandfathered in and the farmers will use it.

Good to know that SMA can handle 240 Delta, hi leg. I diagnosed a system of Schneider inverters connected on delta hi leg, only the A phase to B phase inverter would work, the Schneider must have a neutral between the two hot legs, it will not work with the neutral +/-60 degrees out of phase and +/-60 volts off the correct neutral for that phase. Also the Schneider units must be rewired as 120 volts to work in a 208 volt wye network. SMA obviously made there system more “world centric” rather than be country specific.

Another option I've been looking in to is going 480v 3 phase with inverter at the panels and running that the 900' to a transformer near the house and stepping down to 208v 3ph and using 3 sunny islands instead of 2.

Might be nice to split some of the bigger loads into separate phases.... Gene will turn on currently if the stove(electric), water heater(electric heat pump), and coffee maker are on at the same time. I could split the water heater to line 1&2 and stove to line 2&3.

I have 3-phase 277/480Y in my garage now.
Just received my order of plugs and sockets for 120/208Y and 277/480Y.

That is 3x SI 5048US fed by 120V single phase from the grid, and connected 120/208Y. One SI feeds through power from the grid and the other two SI generate the missing phases.

I have a Sunny TriPower 30000TL-US, which works with either 277/480Y or 480 delta. The lower wattage models require 277, probably drive each phase relative to neutral, while I guess this one drives the 480V.

Three single-phase auto-transformers boost 120V to 277V, and the legs are 480V apart for TriPower.
Those are unpackaged toroids, plan to replace so they can be used for another purpose.

It is limited to 6700W from PV while configured for backfeeding grid, and battery is kept floating while grid is up.
If configured so grid acts as generator and there is no backfeeding, then TriPower could be fully loaded with 30kW of PV, or overpaneled beyond that.

I want to pick up some 10kVA 240/480 to 120/240V transformers (shipping costs from far away and lack of matched sets second hand are the delay). Three of them would convert 120V to 480V isolated, and be connected as delta. It would work like that, but TriPower manual warns that a fault shorting one leg of 480V delta to ground, if not cleared in a short time, is a problem for the inverter - probably the other legs being 480Vrms from ground is too much for filter or surge arrestors.

A fourth transformer with 120V and 240V could be used to establish a neutral, by connecting between one leg (277V) and midpoint of other side of delta (138V). All windings in series <midpoint> 120V + 120V <neutral> 240V + 240V <Line> would give the necessary 1:2 split, with 138V across 120+120 = 240V of winding, and 277V across 240+240 = 480V of winding. The delta would be slightly off center, because transformer turns ratios aren't exact; due to IR drop varying with load, 480V in is designed to give a bit over 240V out under no-load.