Low or high frequency inverter

[455dan]

My compressor is a Quincy QT 5 and with a soft start from SS, will not start either, in fact it made it worse. Buying another 18kpv to run as a pair probably would start but switching to the grid at the shop I can do while still being off grid at the house, cheaper result.

Not sure about his magnums longer term output capabilities but here's the Schneider xw pro 6848:

View attachment 283793

I wonder whether the XW can surge well above the graph's 12KW for say 5 seconds, but it does not show it?

My compressor is a Quincy QT 5 and with a soft start from SS, will not start either, in fact it made it worse. Buying another 18kpv to run as a pair probably would start but switching to the grid at the shop I can do while still being off grid at the house, cheaper result.

That is what I thought. belt drive air compressors are a tough start, While on grid assisted pass through it is no problem for the 18K.
99% of the time grid up no worries at all.

I still want to know if the XW pro can actually DO IT. I will try it when time permits or follow through on post 45.

 

[Crowz]

Who said there was a LF inverter with no idle draw?
I also never saw anyone here claim to have a off grid system with no generator.

I do !

But that is only because the generator got moved to the newest house and I could care less if the stuff runs down at the oldest place

 

[Gttnsun]

I do !

But that is only because the generator got moved to the newest house and I could care less if the stuff runs down at the oldest place

I was referring to previous comments in this thread.
There's no glory in Running a generator, most people attempt to run it as little as possible. For me Wasting power in the rainy weather means running my generator more.

 

[ksmithaz1]

Not sure about his magnums longer term output capabilities but here's the Schneider xw pro 6848:

View attachment 283793

That is pretty fat/ipressive, What the max LRA it can handle is the question. Still say it's going to be borderline on a 6700watt inductive motor.

 

[ksmithaz1]

I was referring to previous comments in this thread.
There's no glory in Running a generator, most people attempt to run it as little as possible. For me Wasting power in the rainy weather means running my generator more.

You were intimating that running two HF inverters to power a really large load was somehow less efficient than running LF ones, in particular if you are off-grid.. Your argument was that you would somehow need an additional 17KWH of batteries to make this work. You stated a 7-day period of no solar on batteries to demonstrate your point as though you would have no other alternatives after 7 days. This is/was pure propaganda. You left out the fact that to run 7 days with a modest load/consumption, for example one where you might actually run the large loads we are trying to start, you would likely need 15 times that to last 7 days. You further left out the fact that no matter the inverter it likely is going to need 1/2 of the 17KW over the same period. Then you intimated that since I am not off grid I don't know what I'm talking about after I mentioned a generator.

If you have to cut on the generator, . . .you have to cut on the generator, that sucks. Even with a single inverter, say 50W of overhead, you still have to run it when you run out of battery, the additional runtime for +50W is going to be measured in minutes. A 10KW generator may have to run an extra 5 minutes to make up for the extra inverter. Maybe. BFD. Again I don't consider this relevant. I still need a generator and removing that tiny load is not going to have any significant impact on whether I will need to turn it on. Or in my case using the grid to make up the difference instead.

 

[Gttnsun]

100w would represent 1.6% more capacity than your load. Insignificant

You are the one that said a 100 watt load was insignificant I was just doing the math for you, 7 days of rainy weather with 100 watts 24/7 is 16.8 kwh
What i am saying is you need twice as much HF inverters to power the same load as a LF
For example one XW pro 34 watts idle consumption, one eg4 6000xp is 50 watts idle consumption you will need 2 inverters to go head to head with a XW pro. Idle consumption 76 watts difference.
This is just one example you can stack up many different brands and get the same result.
Maybe to you it is insignificant but there is rarely any absolutes in solar.

 

[455dan]

You are the one that said a 100 watt load was insignificant I was just doing the math for you, 7 days of rainy weather with 100 watts 24/7 is 16.8 kwh
What i am saying is you need twice as much HF inverters to power the same load as a LF
For example one XW pro 34 watts idle consumption, one eg4 6000xp is 50 watts idle consumption you will need 2 inverters to go head to head with a XW pro. Idle consumption 76 watts difference.
This is just one example you can stack up many different brands and get the same result.
Maybe to you it is insignificant but there is rarely any absolutes in solar.

In the video test where two XW pros were in parallel , Abney said the draw was .7 amps so @~50 volts matches his claim of 37 watts where a single SolArk 12K was using around 70 watts.

 

[seneysolar]

The real off gridders get a gas powered air compressor and dont worry about surge loads....

 

[455dan]

That is pretty fat/ipressive, What the max LRA it can handle is the question. Still say it's going to be borderline on a 6700watt inductive motor.

I found the post where a members 6 HP compressor has LRA of 94 amps and a single XW pro starts it without a fuss.

 

[Brucey]

I found the post where a members 6 HP compressor has LRA of 94 amps and a single XW pro starts it without a fuss.

I would test with dual and then a single 6848 when you get around to testing.

 

[ksmithaz1]

I think where we are missing the point. . . It's overall loss that matters coupled with meeting your maximum demand. Looking at some mythical 'idle consumption' number is meaningless, you have to engineer your system to meet demand.

I have two 18kpv's. Two days ago I just beat it up, batteries were exhausted (poor production X 2 days), I mined full blast and charged my EV. 140 KWH of output on 148KWH of PV. 140/148 = 94.59%.

OTOH a week or so back I barely used any power: 36.4KWH on 40.3KWH of production. Overall efficiency was down 36.4 / 40.3 = 90.32%, about 5% worse. But it doesn't matter, because it is what it is, about a 10% overall loss with low end use, 5+% at the high end.

There should be no actual 'idle' loss, if the thing is idle, turn it off, you are not using it, why have it on? When it is working we need to figure in the efficiency of the unit purely to size our batteries, whatever that happens to be but reality is your batteries are going to need to cover at least 18 hours from 1600-0800 ish. So you need to determine your maximum consumption over that period and and get enough KWH of battery to cover that consumption plus around 30% to stay out of trouble. Any additional battery is going to buy more time, and you can let your 30% drop a bit as you add 'days' of capacity. Thus if you need 35KWH overnight, you get 50KWH of batteries for 1 day, 90KWH for two 120KWH for three. . .

You can scale the idea up or down, but the loss of efficiency is what it is, I don't care what inverter you happen to buy, and if you expect not to run a generator or touch the grid, you are going to want a nice buffer, and that 'idle' number is not going to be relevant. What matters is power in vs power out. Trying to extract efficiency from some published 'idle' numbers is bogus, and using that data to size your batteries is ludicrous. I'm willing to bet pretty much every inverter of any flavor is going to have similar efficiencies to the ones I see +- a percentage point or two.

 

[ksmithaz1]

I would test with dual and then a single 6848 when you get around to testing.

That's a really low LRA. I'm surprised the 18Kpv won't handle it. My 4T lists 120 ish if memory serves, but I would think an air compressor should not be as severe as an HVAC, in particular when it's 120F outside.

 

[sumpower]

Who said there was a LF inverter with no idle draw?
I also never saw anyone here claim to have a off grid system with no generator.

I am off-grid and have never hooked up a generator to charge my batteries. Do not have a grid connection to my inverter. Calculating the panel array size and the battery AH size all went into not needing a generator for my location. On average I have 329 days of sun per year. LF 8Kw inverter with 30 watt idle draw.

 

[ksmithaz1]

Also, I might say on multiple inverters, two will not double your efficiency losses. Since the loss is mostly in the conversion process, more converters does not necessarily equal more loss, assuming both converters are actually participating in the conversion process.

 

[ksmithaz1]

I am off-grid and have never hooked up a generator to charge my batteries. Do not have a grid connection to my inverter. Calculating the panel array size and the battery AH size all went into not needing a generator for my location. On average I have 329 days of sun per year. LF 8Kw inverter with 30 watt idle draw.

Nice, what is your overall PV->Load efficiency?

 

[timselectric]

My system has zero idle draw, because it's never idle. lol

 

[sumpower]

Nice, what is your overall PV->Load efficiency?

During the summer the inverter runs close to 6500 watts during all peak sunlight hours, primary purpose and use of system is pumping irrigation water.
Three total pumps. Two pumps staged to turn on as the day grows brighter. I use smaller solar panels and contactors as the controller to turn on and off pumps #2 and #3. Basically, if a small panel gets shaded the relay turns off the pump. Any excess production during this time goes to the batteries.
The overall load efficiency in the summer averages around 70 to 80%. I have peak loads where the inverter is supplying 8800 watts for 20 minutes at a time. All my equipment is in a temperature controlled room. So I can get away with the high demand loads for 30 minutes at a time and still be within the guideline of manufacturer specifications for the inverter.
Winter overall average eff. is poor, never calculated it. Only serving house and garage loads during this time.
I am not pumping any irrigation water from mid October through March.

 

[jharrell]

I found the post where a members 6 HP compressor has LRA of 94 amps and a single XW pro starts it without a fuss.

The picture you posted of your motor shows a KVA code of D at 6hp 240v is 112 start surge amps, someone in a another thread posted their 5hp Ingersoll with a KVA code L which is over 200 amps surge! Not all air compressor motors are the same just based on HP you have to look at code.

Locked-Rotor Amps (LRA) Calculator and Chart

Calculation of Locked-Rotor Amps (LRA) current and inrush VA of a motor based on its HP and code letter chart.

generators.smps.us

112 amps is 26kw but motor surge is only going to be a few hundred ms not seconds or minutes.

EG4 has a video of a 12k starting a 5 ton A/C no soft start with 137 amp surge seems like no shenanigans had it hooked up to a scope:

 

[455dan]

The picture you posted of your motor shows a KVA code of D at 6hp 240v is 112 start surge amps, someone in a another thread posted their 5hp Ingersoll with a KVA code L which is over 200 amps surge! Not all air compressor motors are the same just based on HP you have to look at code.

Locked-Rotor Amps (LRA) Calculator and Chart

Calculation of Locked-Rotor Amps (LRA) current and inrush VA of a motor based on its HP and code letter chart.

generators.smps.us

112 amps is 26kw but motor surge is only going to be a few hundred ms not second or minutes.

EG4 has a video of a 12k starting a 5 ton A/C no soft start with 137 amp surge seems like no shenanigans had it hooked up to a scope:

Just got back in from the shop talk about dead on...

 

[Gttnsun]

There should be no actual 'idle' loss, if the thing is idle, turn it off, you are not using it, why have it on?

This is not how it works
The specs call it idle consumption but that number is in addition to your loads all day. If your inverter has a 70 watt idle consumption and you are running a 30 watt light bulb you will be consuming 100 watts.

 

[quantum`]

Yes, 'idle' is inverter overhead present all the time.

 

[ksmithaz1]

This is not how it works
The specs call it idle consumption but that number is in addition to your loads all day. If your inverter has a 70 watt idle consumption and you are running a 30 watt light bulb you will be consuming 100 watts.

No, it's not a fixed overhead. Schneider sheet lists 5w or something not connected. Eg4 12kxp list 70w no load with 300v on the pv inputs. The only relevant metric is power in to power out. If I have 10kwh of battery, can I push 9kwh at my loads before it falls over? If pv is producing 1000w, can I push 900 of it too my loads/batteries? Thats the needed metric, other numbers are noise. I'd figure about 90% for most newer HF's. I've used two different flavors, seemed to be pretty close to that for both setups, the 5x5kw and the 2x12kw, with a nominal actual load. I can't speak to the LF/Schneider. My understanding was it was slightly less efficient due to xformer loss.

 

[Gttnsun]

There is the power it takes to have the inverter on then there is the efficiency at which the inverter can change dc to ac.
They are 2 different things.
Where HF inverters win is the ability to pull loads directly off the high voltage bus bars, so you have 400v DC to 120v ac directly. If you are charging the batteries it still is 400vdc to 48vdc to 120v ac same as a LF inverter.

 

[SilverbackMP]

The real off gridders get a gas powered air compressor and dont worry about surge loads....
View attachment 283865

I want a large compressor for plasma cutting…I don’t think that tank’s gonna do it lol.

 

[Daddy Tanuki]

I want a large compressor for plasma cutting…I don’t think that tank’s gonna do it lol.

and you want it dry if your consumables are going to last.