120V Flux Welder, 2000W Inverter. What?!!

[OffGridForGood]

This is very interesting,
If @12VoltInstalls was running 'close to the limit' with his 2000W inverter, and needed a bit more capacity to run his Mig, could he add the PFC to that set up, instead of upgrading to 3000W inverter, perhaps at lower cost?

 

[Hedges]

I never said PFC was cheap. This one is $242 for 1500W, AC to 360VDC which we then fed into the AC input of an SMPS. Can parallel multiple modules for more watts.

https://www.digikey.com/en/products/detail/tdk-lambda-americas-inc/PF1500B-360/17128332

After a forum member pointed out the earlier 1000W product line, I bought a few from eBay seller in China or $25 each, so those were affordable. Objective was to clean up my VFD pool pump so it wouldn't upset Sunny Boys.

What we need are products that have PFC built in for modest additional cost.

I think he's better off getting a bigger inverter.

I briefly thought a cheap MSW inverter would be good to feed these non-PFC SMPS loads, but then I realized the dead time lets capacitor voltage draw down, so every phase the inverter closes a FET between its charged caps and loads not fully charged caps. You don't want to short two capacitors together.

A true square wave inverter would be better, no time to discharge. Tapping directly into HV DC bus should be the best.

 

[12VoltInstalls]

This is very interesting

To my way of thinking I’d elect to not regularly use a 2000W inverter at or near 2000W on purpose. Optimistically that’s 16.x amps and 3000W is like or near 22.x amps.
Just seems like a more relaxed inverter will be a lot easier to live with day to day if I want to get along and not have it be moody. I just want to have it put out when and where I want without it shutting me off, or just ending things altogether, like we never knew each other at all

 

[OffGridForGood]

What we need are products that have PFC built in for modest additional cost.

I think he's better off getting a bigger inverter.

That would be an interesting development - if wide use of solar lead to changes to common equipment like A/C and heat pumps for example - an option to buy the equipment with internal PFC.
If he pays 800 for a new inverter, wouldn't the PFC for his Mig be cheaper option using the existing inverter? more to it?

 

[OffGridForGood]

After a forum member pointed out the earlier 1000W product line, I bought a few from eBay seller in China or $25 each, so those were affordable. Objective was to clean up my VFD pool pump so it wouldn't upset Sunny Boys.

did it work?

 

[Hedges]

If he pays 800 for a new inverter, wouldn't the PFC for his Mig be cheaper option using the existing inverter? more to it?

More to it. Two of the 1500W PFC modules needed for the wattage, and design & build EMI filters from inductors and capacitors.
After my intern designed PCB, first estimate of fab through DigiKey was $1000. Using a China based vendor suggested by a colleague, it was only one or two $hundred for 20 boards. Might be possible for just about $800.

We fed its 360VDC straight into our AC powered product, but were careful not to use the AC rated switch, and didn't blow the AC rated fuse built into SMPS.

It would be nice if an economical PFC was available fully integrated, but the safety & reliability issues of feeding DC into AC products are a problem. Would need to be an AC/AC on-line switcher (UPS sans battery) to be a product.

A possibility is to tap into HV bus of his HF inverter and use that. Don't want to suddenly connect capacitor to capacitor, that would have inrush surge. For precharge could connect through a lightbulb to charge it up, then short out bulb. Or connect prior to powering on inverter.

 

[Hedges]

did it work?

Haven't tried feeding VFD. Just attached output capacitor to PFC module and fed AC, heard it clicking but didn't deliver voltage.

The older model I bought has outputs that need to switch an input precharge circuit. Basic PFC is a boost converter into capacitor which will be maintained above Vpeak. When first connected to grid it tries to yank capacitor up to peak. So I need to build a circuit around it.

The newer one has that basic support circuitry built in. Only EMI filters are external, and those aren't needed to simply function.
Our intern was able to hand wire one on a breadboard and we tested it powering our equipment. The PCB fabs just made a cleaner assembly. I think the waveforms were decent. We were actually focusing on line frequency and harmonics - any DC power supplies fed by AC carry some level of 120 Hz.

 

[12VoltInstalls]

If he pays 800 for a new inverter

I think there’s a couple ‘cheap’ low frequency inverters on the market for that money.
The QZRELB stuff varies wildly month-to-month ~$300 to ~$400 for the HF 3000W; the 2000W does everything it’s supposed to do including shutting down and ‘soft start’ runs my cheapo lightweight craftsman tablesaw, a big-ish ShopVac, and the Makita compound saw.

So I have reserved faith the 3000W will be just as good. My only real hesitation is that I’m not sure I want to part with that money or jump forward and get the split phase MPP unit for the shop that I intend to do next summer. With the ‘other’ currently not installed 2400W of panels, on good sun days the batteries might not even notice I’m using any power?!

The little scientist/hobby guy/experimenter down inside me wants to just order the 3kW yesterday but I’m actually trying to build a second building next month and it’s unclear that won’t take up all my cash anyways…

 

[HarryN]

The inverter is actually the smaller of your risks.

The bigger risk is the BMS on your batteries. Spikes will go right through the inverter and hit the BMS hard without tripping any breaker as they are very fast. A very fast fuse might catch it. I have had a customer blow out some LiFe battery bms before with a setup that did some spikes that no one expected to happen and even the battery supplier was surprised that it damaged the BMS.

I am not trying to spook you away from doing this, just pointing out where the risk is in your setup so that you can look for / deal with it as you work with it. I have thought about doing similar things but haven't.

Not sure if a big audio cap in between the battery pack and inverter would help or not - I read that some people on this forum are doing it but no experience. Might cause other challenges like larger pre-charge issues.

 

[OffGridForGood]

Not sure if a big audio cap in between the battery pack and inverter would help or not - I read that some people on this forum are doing it but no experience. Might cause other challenges like larger pre-charge issues.

From what @Hedges is saying above, there is more to it than just 'slapping' a capacitor into the circuit. I did a few more tests today to push the little MPP 2724 to it's limits, some of the universal motors seem pretty hard on it - 14" chop saw was one of the worst, although I learned by trial and error if you just touch the trigger for a second, and let go, and then pull it again while the blade is sort of spinning, it would start it without going into overload fault lol likely hard on the BMS without me even knowing it! This mobile unit has a 304Ah 8S DIY battery pack with a Daly 150A BMS, 125A DC dual direction breaker and a 125 Class T fuse on it. None of those triped during my punishment test.

My only real hesitation is that I’m not sure I want to part with that money or jump forward and get the split phase MPP unit for the shop that I intend to do next summer. With the ‘other’ currently not installed 2400W of panels, on good sun days the batteries might not even notice I’m using any power?!

If you want a split phase MPP in a single unit I gotta say I am impressed with my 6048's they do it all and I don't baby them. They are $943USD each and they often have inventory in US warehouse. Idle consumption is pretty high - I average about 75W continuous, bit lower than this at night with few loads, bit higher when pushing them hard. The 6048 outputs 120/240 with just a single inverter, quite handy.

 

[Hedges]

Capacitor on battery cable might reduce surge from battery, but especially with a "stiff" lithium battery, it can't supply much current unless massive. Maybe supercap can do it.

Capacitor on HV rail of HF inverter might help.

Neither of those reduces the higher current that trips breaker or overloads inverter due to low PF. For this issue, fancier PFC design could help. Or bypass conversion to sine wave, just feed HV DC to load.

14" chop saw was one of the worst, although I learned by trial and error if you just touch the trigger for a second, and let go, and then pull it again while the blade is sort of spinning, it would start it without going into overload fault lol likely hard on the BMS without me even knowing it!

Brush type motor? If 240V, should start and run on 120V, less current. If 120V, step-down transformer and switch from 60V to 120V once running. Series resistor might reduce current during starting (but burns a lot of watts.) Consider Antherm NTC thermistor. Consider a dimmer type circuit (but this application is heavier than most.)

 

[OffGridForGood]

Capacitor on battery cable might reduce surge from battery, but especially with a "stiff" lithium battery, it can't supply much current unless massive. Maybe supercap can do it.

Capacitor on HV rail of HF inverter might help.

Neither of those reduces the higher current that trips breaker or overloads inverter due to low PF. For this issue, fancier PFC design could help. Or bypass conversion to sine wave, just feed HV DC to load.



Brush type motor? If 240V, should start and run on 120V, less current. If 120V, step-down transformer and switch from 60V to 120V once running. Series resistor might reduce current during starting (but burns a lot of watts.) Consider Antherm NTC thermistor. Consider a dimmer type circuit (but this application is heavier than most.)

It's a Milwaulkee metal cutting shop saw - looks like a regular saw blade like you would use for wood, but this cuts regular mild steel (angles, channels, flat bars) up to half-inch thickness (the manual says, HA!, yeah I cut some 1" x 2" flat bar with it anyway LOL.)
Like this one:
(different brand, but similar, I suspect these all use universal brushed motors, and take a whopping in-rush current to start the 14-inch blade spinning)
I don't have a meter that can capture the in-rush current - too fast for my meter. Actually if anyone can recommend a meter that can measure in-rush, and isn't a zillion dollars to buy, actually I just checked and the Klein CL900 multimeter is on sale right now, wow, so tempted.

 

[12VoltInstalls]

Neither of those reduces the higher current that trips breaker or overloads inverter due to low PF

some of the universal motors seem pretty hard on it - 14" chop saw was one of the worst, although I learned by trial and error if you just touch the trigger for a second, and let go, and then pull it again while the blade is sort of spinning, it would start it without going into overload fault lol

That’s what I had to do with the little craftsman tablesaw on the 1012LV-MK

FWIW that same 10” tablesaw along with the 10” makita compound start fine on the QZRELB 2kW inverter.

If you want a split phase MPP in a single unit I gotta say I am impressed with my 6048's they do it all and I don't baby them. They are $943USD each and they often have inventory in US warehouse. Idle consumption is pretty high - I average about 75W continuous, bit lower than this at night with few loads, bit higher when pushing them hard. The 6048 outputs 120/240 with just a single inverter, quite handy.

watts247.com had something (5000W?) that was also LF inverter. Or was that solark?!
Anyways, probably will buy watts247 whatever whenever I do the shop system.

bigger risk is the BMS on your batteries

will be going back to 3 batteries in parallel shortly, so 3x100A BMS will be sharing the load, whatever it is. But I hadn’t really thought about that. But could it be actually 300A on startup?

Current temp setup is an 80’ 12ga extension cord. (When I do The Dig I will have about the same length of 10ga thhn feeding the shop underground.) The extension cord might disguise a small part of the surge? Like resistance may act like a buffer?

not trying to spook you away from doing this, just pointing out where the risk is in your setup so that you can look for / deal with it as you work with it. I have thought about doing similar things but haven't.

no issue. I started the thread to discuss this. I know enough to know what I don’t know; I’d like to find out about what I don’t know.

Incidentally, Saturday evening while I had chicken on the grill I used a thermostatically controlled 1500W electric skillet to braise some fresh green beans and zucchini. All told it ran 1/2 hour-ish. No problems with that either.

 

[Hedges]

It's a Milwaulkee metal cutting shop saw - looks like a regular saw blade like you would use for wood, but this cuts regular mild steel (angles, channels, flat bars) up to half-inch thickness (the manual says, HA!, yeah I cut some 1" x 2" flat bar with it anyway LOL.)
Like this one:
(different brand, but similar, I suspect these all use universal brushed motors, and take a whopping in-rush current to start the 14-inch blade spinning)

Nothing like an induction motor though. Or, if the inverter is willing to keep operating with sagging output, brush type motor will still start and run.

Try my suggestion of step-down transformer. A 120/240 or 240/480 pair of primary windings in series makes a 2:1 autotransformer.

Midnight showed off Rosie starting 4x DeWalt 1.5 HP compressors all at once. (brush type). Or apparently a single well pump.

I don't have a meter that can capture the in-rush current - too fast for my meter. Actually if anyone can recommend a meter that can measure in-rush, and isn't a zillion dollars to buy, actually I just checked and the Klein CL900 multimeter is on sale right now, wow, so tempted.

I got the HF Ames 1000A clamp meter for $100

check all panels are connected and working on fronius 27kw

we have a Fronius 27kw inverter connected to the grid with 90 x 375w jinco panels. The installer is no where to be contacted anymore. All this time, the inverter was not connected to the internet as there was no internet close to that building. Now I have connected the inverter to the internet...

diysolarforum.com

 

[OffGridForGood]

Yes, I expect PF to depend on load, not power source (so long as a sine wave.)

Whatever RMS current draw is measured is the actual current draw (assuming true RMS meter).
To deliver 1200W at 120V into a 1.0 PF resistive load would require 10.0A
If 0.85 PF load, 11.76

Well I used all this talk about in-rush and PF and 'true load RMS' as justification for a new meter, bought a Klein CL900 with the max/min and in-rush functions. Then I just had to know - so connected up the Mig-10 again, and ran the B, C and D settings to see what the Klein had to say about the max current in each setting, I repeated each test three times and took the highest values:
B - 16Amp
C - 20Amp
D - 25Amp
Then for good measure opened the Load Centre Panel and got the in-rush on my big air compressor, the well pump and even the Fridge starting - since I just 'Had to know'
6Hp Air compressor - 43.3A 240v
Well pump - 17.2A 120v
Fridge - 10.1A 120v
*yeah I am somewhat OCD but that is how I got here!

 

[OffGridForGood]

Okay, since we talked about that Milwaukee metal chop saw, I figured, "I gotta know" - what is the inrush to start this up?
Actually how about a few common tools while we are at it:
All of the following are 120v AC load tools from around the shop, each number is max value from three tests, no load (not cutting/drilling working)
Big Dewalt 14" wood cutting chop saw FLA 15A, in-rush 32.2Amps
Milwaulkee 14" metal cutting chop saw FLA 15A, in-rush 52.4Amps (WOW)
The same Milwaulkee 14" metal cutting but using the bump-start pull the start, pause a half-second and pull on again in-rush 40Amps !
Hitachi 1/2" drill (550rpm) FLA 6.2, in-rush 11.2A
Dewalt 1/2" Impact FLA 7.2A, In-rush 7.6A
10-gallon shop vac FLA 15A, in-rush 22.2A
4.5-inch mini angle grinder FLA 6A, in-rush 12A
Milwaulkee 7-1/4" skillsaw FLA 15A, In-rush 33.9A
Bosch worm-drive 8"skillsaw FLA 15A, in-rush 37.3A
Floor model General 2Hp radial drill press - set to mid-speed 1200rpm FLA on the motor is 15A, In-Rush 12.8A
Cheap Chinese drill press, 3/4Hp (no FLA number on it) In-rush 17.3A

 

[Hedges]

Can you try a transformer stepping down 120V to 60V to start the brush-type motors?

 

[OffGridForGood]

Can you try a transformer stepping down 120V to 60V to start the brush-type motors?

What can I use for this test?
I can't think of any 120-60volt transformers laying around that would be big enough capacity - ie I have the bench source which takes 120v but makes up to 60vDC, and it is only 5Amp
I suppose a 240 to 120v transformer would also function as a 120 to 60?

 

[OffGridForGood]

If we cut the voltage in half doesn't this double the amperage (current) the motor will pull? or is there a limit to the current upon start up - that inrush where the current will hold steady and the lower voltage would reduce the in-rush total energy to start the motor?
I recall changing over a motor - it came capable of 120 or 240v, it was factory wired 120 and I followed the diagram inside the motor control housing, swapping it over to 240, which reduced the running amperage by half, and put equal load on both L1 and L2 at the panel - which my inverters prefer.

 

[Hedges]

Starting surge or locked rotor amps I = V/R
Half voltage will cut the current in half. Should be good for brush-type motors.
(Induction motors might fail to start. I think 3-phase motors without heavy load do start, though.)

Also a transformer with 120/240V primary windings could have them wired in series (240V), be fed 120V, then center tap is 60V.
(doesn't matter what secondary, just leave that open circuit.)

One sized so 240V input current is 1/2 of your motor's running amps could be sufficient. I think that means VA rating similar to the tool (likely up to 1800W, so not a small transformer. But you can try a smaller one, see what happens for a brief start, don't let it run long enough to overheat.)