Split Phase Grid input, 480Y277 output

DIY
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1

Hey folks,

I wanted to make sure my scheme to use victron quattros to provide 480V 3 phase from batteries (and maybe more), while charging from split phase, is possible/makes sense.

A bunch of context:
I am in the US and have a large home shop where ~everything is run 480V 3 phase. Lots of significant (for a home shop) HP machines (metalworking CNC, woodworking CNC, etc). I currently use about 40KVA of 480v 3 phase. I can actually get utility 230V 3 phase, but not at a reasonable cost (it would be about 60-75k). Instead, I have 800 amp split phase service (which had cost about $1500 to have done). We are at the literal end of the line for power service, so ~any outage anywhere on our line always affects us.

The shop 3 phase is currently produced from 225amp split phase through the following scheme:
230V Split Phase → 230V Isolation Transformer[1] → 54KVA Phase Perfect → 230V 3 phase to 480V step up transformer.

The phase perfect is nearing the end of it’s life. Replacement is about 20-25k. Simultaneously, i was also exploring both battery backups for the house/shop, and doing peak demand shaving (because of my TOU tariff, peak demand shaving would save me about 300-500 a month, more in summer months), plus maybe some solar (we have slate roofs, can’t do roof solar, but i have other areas).

I was thinking of getting a 50kwh (or whatever, depending on how long we want house/everything to run without charging) battery cabinet, use 1 quattro 277 inverters per phase to provide 480V 3 phase from it, and charge the batteries at night from the grid 230v split phase. Will this work? It looks like it should by the manuals, and messing about with the demo systems in ve configure, it seems like as long as i tell them not to switch as a group, this should work.

It also looks like, as long i’m careful not to exceed max charge/discharge currents, and am careful about wiring, i could also hook up inverters to provide 230v split phase from the same battery cabinets and interpose it between the home and the grid to provide peak demand shaving/battery backup for the home as well (and if needed, only charge the batteries from this part of the setup instead of from the 277 part, keeping the 277 part in inverter only mode)

But reality is sometimes different, so figured i would ask if this is possible, and if there is a horrible downside i’m missing.

Efficiency wise, if the datasheets are correct, on the 480v side, this is actually a bit more efficient than my current system because of my current transformer losses/etc.

You can also assume i’ve done the cost math on all of this, and because of how much electricity we use/time of use tariffs, the payback period would be quite short (<5 years at current costs). Compared to buying a new phase perfect, it’s basically a wash to buy inverters + battery pack, and it seems the longer i wait, the better the batteries + inverters come out cost wise.

[1] While the phase perfect is low THD output, it does couple plenty of noise onto the input at this size phase perfect. I’ve had long, drawn out discussions with phase perfect about this, using my fluke analyzer data to show them that it is their unit that causes it, and the end answer from them is “yes, and that sucks, such is life”. To avoid this affecting the house lights/etc, i currently use a 240->240 isolation transformer before the phase perfect.

2

Im from europe, so split phase is not something i know from direct experience. But feeding only 230V to a 277V Quattro will not be enough voltage for it to consider the grid good. Even if it would, this would also mean that the output would come down to the same 230V.

However, you can use a triplet of 277V Quattros to generate your 3x277/480 and use one or more 230V MP/Quattro to feed the DC side from mains. Or use chargers on the mains side.

But keep in mind that this wont be an efficient process, i guess you would be loosing about 20% of input power to heat losses in the inverters, batteries and cables. Also idle consumption would probably be above 400W (one 277V Quattro alone is rated at 110W idle consumption).

But since you already have a 3x230V to 3x480V transformer, you might be able to reuse that and build a 3x230V victron system. A threephase system can be setup to run on a single phase on its input, using one MP as an inverter/charger and the two others solely as inverters, passing the necessary power through the DC side

3

Thanks!

The 277 datasheet says it will be okay with that ac input voltage level of 240-295 and mine would be 250 (grid voltage is high in my area. I actually tap it down on the isolation transformer ).I’ll double check this is not a datasheet bug with victron.

Efficiency wise i already lose that amount to the transformers and phase perfect (total idle loss is around 1kw at no load) so it’s net the same or better there.

If i also power the house ( 3 277 Quattro for the three phase for shop , two split phase Quattro for the house load), I would just only use the split phase Quattros to do charging and avoid any input voltage issues there.

The tou on peak vs off peak cost difference is huge (15cents on peak, 1 cent off peak), so even if efficiency loss was actually 20% more than now it would still make up for it at the current relative amounts of on peak vs off peak over the past few years (Ie 1.2 * all usage which will now be off peak is still wildly less expensive than 1.0x current off peak + 1.0 x current on peak). I am guaranteed this rate for a long time.

4

That was a long post and I will admit that I didn’t read it all. Dealing with multiple voltages is the easy part so long as the phase rotation is the same. But dealing with the phase rotation issues is where you will have fun (not).

Most modern electronics can handle 208V double phase or 240V single phase. However, your A/C compressor or other motorized appliances might not. If you are confident that you can run 208V/120V inside the house, then it’s an easy project. You get a 480V to 208V three-phase transformer with a neutral on the 208V side to make 120V line-to-neutral. If not, you have to handle converting three phase to single and split-phase power.

If you ONLY have three Quattro 15kVA 277V inverter/chargers, then to charge with your 240/120V service you would need a transformer to go from 240V to 277V and only one of three Quattros will charge. If you use the shop tools a few hours a day and can keep up with charging batteries over 24hrs then this might work for you.

Otherwise you will end up with a two VE.Bus system. VE.Bus #1 can be two or more Multi/Quattros in split-phase mode that can provide 240V/120V to loads and charge the battery bank from mains or solar. VE.Bus #2 will be three Quattro 48/15000 277V in three-phase configuration supplying loads to your shop equipment.

This is greatly simplified, but I hope it answers your questions. To design such a system is far beyond the scope of the Victron Community. I would urge you to work with your local Victron installer or distributor. If you don’t have one, then find one to help answer your questions and help you design an efficient and effective system that meets all of your needs.

And have fun with this. It sounds neat :slight_smile:

5

At least by the data sheet, this part appears wrong. I agree that only one will charge. But the datasheet claims the 277 quattro can accept 240-295v input, so i at least theoretically should not need to transform it because it will see 245-250v from the grid (at least here :P)

I was actually mildly surprised by this (as it seems you were), so i have an email in to victron to try to verify the datasheet is not in error.

Overall, the shop is essentially “light commercial” already, so i’m very used to having to deal with fairly complex electrical system design for it :slight_smile:

6

You could be right. I didn’t check the datasheet. The voltage range might work and eliminate the need for a step-up transformer for that phase. That’s the least expensive part haha. But the rest is true. If you don’t need to provide 240V/120V to the home from the inverters (which I thought you also asked about) then the three Quattros for 480V will work.

The idle power draw from these 15k’s will be huge so make sure you account for that if you leave them running all the time. That’s one unit I haven’t actually measured. Don’t be surprised if it’s standby draw is 2x or more than the published spec.

7

If i power the house, i’m going to do it through a bunch of separate multiplus split phase inverters (the 2x120’s), hooked up to the same battery, not try to take the 480 3 phase and down convert it.
You are right this part is the least expensive part of this fun endeavor :slight_smile:

Yeah fair, just for the shop, the currenet total draw of the 240v isolation transformer, the phase perfect, and the 480v step up portions is 1kw at idle, 1.5kw on average, and would be more at full load.

The phase perfect alone is 620watts total idle power loss. The quattro 277 claims 110watts idle loss, so if i had 3 of them, and each was double the published figure, it would be the same as the phase perfect.

That seems about right, so i suspect your 2x over published figure is probably right.

8

Keep in mind that those only output one 120V phase when inverting. They pass through a 120/240V mains but the inverter is just 1x120V.

If you want true 120/240V splitphase you need two 120V units running in 180° two-phase mode

9

Ah, you are right, i admit i hadn’t read the datasheet/description for it yet.

Looks like that part will require a bunch of pairs of the 48/5000va 120v multiplus-ii’s in 180 dual phase mode to provide split phase load needs.