How about Using a 1-Phase 120V to 3-Phase 240V Converter Instead of Parallel Inverters?

[forbin]

I want to run my well pump off solar. The Inverter I have in mind has enough power, but it only outputs 1-Phase 120V. I can buy a converter to turn 1P 120V into 3P 240V for about $300. Wouldn't that be a lot more economical and space efficient than trying to parallel inverters? What am I missing?

 

[Rednecktek]

What am I missing?

Phase sequence. A split phase output from a paralleled set of inverters or an autotransformer gives you two waves of AC at 180deg off, so when one is peaking the other is at bottom.

On 3-phase your waves are 120deg off so when one leg is peaking the other two are only 2/3 of the way to where they're going.

Many people get the 240v versions of AIO's and put the 240v through an autotransformer to split the output into the two opposing wave forms, not uncommon at all.

 

[forbin]

Phase sequence. A split phase output from a paralleled set of inverters or an autotransformer gives you two waves of AC at 180deg off, so when one is peaking the other is at bottom.

On 3-phase your waves are 120deg off so when one leg is peaking the other two are only 2/3 of the way to where they're going.

Many people get the 240v versions of AIO's and put the 240v through an autotransformer to split the output into the two opposing wave forms, not uncommon at all.

Thanks for the feedback! My brain gets twisted several times per day as I go through this process. So how does that apply to running my well pump? It sounds like you're saying there's a difference between the 3-Phase 240 you get from running a 120V AIO through a device like this....

3 hp VFD, Single Phase 120V Input, 1ph/3ph 220V Output

3 hp single phase 120v input, single phase and three phase 220v output variable frequency drive, specially designed for 120v power supply, manufacturer direct sale.

www.ato.com

...and the 3-Phase 240 output you get from a 240V AIO running through an auto-transformer.

 

[fromport]

I want to run my well pump off solar. The Inverter I have in mind has enough power, but it only outputs 1-Phase 120V. I can buy a converter to turn 1P 120V into 3P 240V for about $300. Wouldn't that be a lot more economical and space efficient than trying to parallel inverters? What am I missing?

You could use an auto transformer
I couldn't find this item on the website of the manufacturer, but found this on a website of _a_ reseller:

Midnite Solar Midnite Sunny Island 6000w Autoformer - MNX-240 Autoformer

Midnite Sunny Island 6000w Autoformer - MNX-240 Autoformer

unboundsolar.com

It will turn 120V -> 240V
It will eat energy when nothing is using 240Volt.
It is heavy and not cheap

 

[Rednecktek]

..and the 3-Phase 240 output you get from a 240V AIO running through an auto-transformer.

That's what you're missing. If you look at wave forms a split phase 240v is 2x 120v legs at exact opposite ends at any given time and is often referred to as "Single Phase 240v" as below:




What you're looking at is 3-phase and the waves are 120deg off of each other, like so:


Your 240v well pump is wired with 2 coils opposing each other so when the top of Leg1 is at its highest it pushes on Coil1 to move the motor around. Half way around the top of Leg2 pushes on the coil again and spins it back around to Leg1 and its coil and on and on and round and round it goes.

With a 3-phase motor it does the same basic thing but there are 3 coils that "push" off the wave.

If you were to try to run a split phase motor off of 3-phase power then Coil1 would hit just fine but when Coil2 tried to push off, it would be half way between waves and wouldn't get the power it needs.

What an autotransformer does is split the incoming single wave form through a delay on a second leg thus creating the second leg out of phase, basically taking power through a splitter and pausing the frequency 1/120th of a second on one leg.

In basic general terms. Now I have to go hide from all the angry EE's about to descend upon me with righteous fury.

 

[J.P.]

Please check your pump specifications. There is a very high probability that your well pump is SINGLE PHASE (1P) 240V (often called split-phase) but it is still single phase nonetheless.

Also, don't confuse 3 wire with 3 phase. There are 2 wire, 3 wire, and 4 wire well pumps but none of those have to do with phase. Most all residential applications in the US are 120V/240V SINGLE PHASE power.

Now as to your original question about how best to get 240V to power your well pump, there are a few options. I solved that problem by purchasing an inverter that had 240V (split phase) output. This is (2) 120V output legs that are 180deg out of sync. Just like the utility power that is coming into your home now.

 

[Brett V]

I struggled with this as my old 24 volt system had enough power for the necessities in the house but I couldn't run the well pump. I had considered replacing the pump with a 120 volt option but by the time I replaced the pump and upgraded the inverter to handle the startup surge, it was cheaper and much more efficient to scrap the 24 volt system for a Growatt 6 kw AIO.

 

[Rednecktek]

It's really confusing too when the same words are used for different incompatible things in the same world. Motors are one of the best examples of this AND some of the most frustrating.

American "Single Phase 240v Motor" requires 2 hot legs at 120v each at 180deg out of rotation

BUT

European "Single Phase 240v Motor" is a single hot leg at 240v and a Neutral leg at 0v.

They CANNOT be interchanged!

Same words, same description, completely different things. ?

 

[Supervstech]

It's really confusing too when the same words are used for different incompatible things in the same world. Motors are one of the best examples of this AND some of the most frustrating.

American "Single Phase 240v Motor" requires 2 hot legs at 120v each at 180deg out of rotation

BUT

European "Single Phase 240v Motor" is a single hot leg at 240v and a Neutral leg at 0v.

They CANNOT be interchanged!

Same words, same description, completely different things. ?

However...
Euro single phase motors don't know the difference with us split phase electricity...
The motor won't care. Both are single phase 240...

Ya just can't get 180degree 120v out of the euro source.

Us 240 is NOT two 120V 180 phases.
It is a single 240V phase that ALSO has a midpoint where 120V can be derived from the opposing peaks of the 240

 

[Horsefly]

Ok, so I'm an EE but my training is in microelectronics and satellites, so some of this stuff doesn't come naturally to me.

I get split-phase 120V/240V, but I thought 3 phase in the US was considered to be 208V, and assumed it was because of the 120° phase shift between the three lines. I guess I should read up on this...

I guess I'm a little bit skeptical that @forbin actually has a 3 phase 240V well pump. Not many homes have 3-phase at all. It seems more likely that he has a 240V well pump, and the solution is much simpler than we are all making it.

 

[Hedges]

As others said, your pump may be 240V single phase (also can run on 120/240V split phase.)
If your motor is 240V single phase, a suitably heavy passive transformer should do the job.

Or, it could be 3-phase.

I'm surprised that converter says 220V output from 120V input. Most VFD just switch transistors PWM into a motor, don't have an inductor to boost voltage.

Does your AOI put out the wattage needed to run the motor?
Does it put out the wattage/amperage to start the motor, "LRA" locked rotor amps or about 5x nameplate operating amps?

If it is a 3-phase motor and you get a VFD, that starts the motor gradually without surge. But, 100% of the current it draws from sine wave input comes when input voltage exceeds voltage fed to motor, rectifier capacitor front end. Your inverter may or may not be happy with that.

There are 3-phase PV direct drive setups for pumps. Grundfos offers complete packages. Some companies sell VFD with PV input and MPPT algorithm.

 

[circus]

Think of US single phase as 240 volts. 120 volts of a wall outlet as half. Three phase is for industry or commercial using lots of power.

 

[MichaelK]

Forbin, what are the specifications for your well-pump? Starting surge, running amps, hp, 2-wire/3-wire, ect. Don't start asking for product recommendations till you have all of those numbers.

I have a Schneider XW+6848 that has successfully powered my 1hp Grunfos well-pump for years now, solely via solar. Rock-solid product designed to last decades.

 

[forbin]

Please check your pump specifications. There is a very high probability that your well pump is SINGLE PHASE (1P) 240V (often called split-phase) but it is still single phase nonetheless.

Also, don't confuse 3 wire with 3 phase. There are 2 wire, 3 wire, and 4 wire well pumps but none of those have to do with phase. Most all residential applications in the US are 120V/240V SINGLE PHASE power.

Now as to your original question about how best to get 240V to power your well pump, there are a few options. I solved that problem by purchasing an inverter that had 240V (split phase) output. This is (2) 120V output legs that are 180deg out of sync. Just like the utility power that is coming into your home now.

That is very interesting feedback. The pump is a Pentair PenTek XE Series 1 HP, which the spec sheet claims is a 3-Phase motor. However, I'm currently running it from a Champion 6250W 120/240W generator, which its spec sheet claims is single phase. Color me confused.

 

[Supervstech]

That is very interesting feedback. The pump is a Pentair PenTek XE Series 1 HP, which the spec sheet claims is a 3-Phase motor. However, I'm currently running it from a Champion 6250W 120/240W generator, which its spec sheet claims is single phase. Color me confused.

Yeah… unless there is a three phase inverter on the pump, 240V single phase power would burn it up in seconds if it’s a 3Ph motor…

 

[forbin]

Ok, so I'm an EE but my training is in microelectronics and satellites, so some of this stuff doesn't come naturally to me.

I get split-phase 120V/240V, but I thought 3 phase in the US was considered to be 208V, and assumed it was because of the 120° phase shift between the three lines. I guess I should read up on this...

I guess I'm a little bit skeptical that @forbin actually has a 3 phase 240V well pump. Not many homes have 3-phase at all. It seems more likely that he has a 240V well pump, and the solution is much simpler than we are all making it.

Your skepticism is warranted, and my confusion level is reaching a peak. As I mentioned to J.P., the pump is a Pentair PenTek XE Series 1 HP, which the spec sheet claims is a 3-Phase motor. However, I'm currently running it from a Champion 6250W 120/240W generator, which its spec sheet claims is single phase. I feel like John Travolta in that meme where he;s looking left and right.

 

[labeeman]

I want to run my well pump off solar. The Inverter I have in mind has enough power, but it only outputs 1-Phase 120V. I can buy a converter to turn 1P 120V into 3P 240V for about $300. Wouldn't that be a lot more economical and space efficient than trying to parallel inverters? What am I missing?

That would work fine and you can program the inverter to do a soft start so as not to hit your 120 inverter with a bunch of amps that it cannot handle. I have used single-phase to three-phase inverters for several projects for my machines.

 

[efficientPV]

That is available in that HP in either single phase split capacitor or three phase. Only you know what you bought.

 

[labeeman]

Your skepticism is warranted, and my confusion level is reaching a peak. As I mentioned to J.P., the pump is a Pentair PenTek XE Series 1 HP, which the spec sheet claims is a 3-Phase motor. However, I'm currently running it from a Champion 6250W 120/240W generator, which its spec sheet claims is single phase. I feel like John Travolta in that meme where he;s looking left and right.

If you are running it off of your single phase gen then you DO NOT HAVE A 3 phase motor and cannot use a single phase inverter to three-phase inverter Money down the drain.

 

[forbin]

That would work fine and you can program the inverter to do a soft start so as not to hit your 120 inverter with a bunch of amps that it cannot handle. I have used single-phase to three-phase inverters for several projects for my machines.

There's a puzzle piece I was missing. I've heard the phrase "soft start" tossed around (the tech from Pentair mentioned it, but didn't know what it was) but you're the first person to indicate that it is something that can be programmed into some inverters. Now I need to check my proposed inverter to see if it has that feature. FYI, I'm currently looking at an MPP L6548.