Author Topic: Running power tools like mitre saw off an inverter  (Read 677 times)

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Offline Red Squirrel

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Running power tools like mitre saw off an inverter
« on: May 22, 2019, 02:43:07 am »
How hard is it to run big tools like that off an inverter, I'm thinking the startup surge might be a lot to handle.  If I go with a good 2000w inverter with say 3000-4000w surge should I be pretty much good to go?  Or do I need to grossly oversize?   I would be getting pure sine.  Just looking at inverters on Amazon to get an idea, the price ranges are quite wide, I assume I want to pay about a grand for a 2000w inverter for good quality, but I see some for as low as like 300 bucks are they worth considering or should I stick with the bigger brands like Xantrex, Samlex etc?    Also from a performance stand point any major differences between a 12v model and 24v model?  The 24v will pull half as many amps from the battery so I imagine it will have a little bit more performance due to less voltage drop and also be less hard on the battery.  I will be running this off a solar system and my charge controller supports 12v or 24v so either one works, but if I go with 24v I will have to upgrade my battery setup.
 

Offline dirtcooker

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Re: Running power tools like mitre saw off an inverter
« Reply #1 on: May 22, 2019, 04:41:30 am »
>Or do I need to grossly oversize? 
It depends on the inverter. This Sigineer APC6024D 6KW inverter is rated for an 18KW surge for 20s. This is a ferroresonant transformer based unit that weights roughly 80 lbs and is extremely rugged. This model has been rebranded by Aimscorp and Golden Power among others, but you can order directly from Sigineer and shipping is super fast (approx 5 days from Shenzen). I bought one for my off-grid summer place.
One downside to this for solar applications, which is a problem with most all transformer based units, is high no load power draw. The unit draws 96W at 24v input, (4A dc input) with the inverter running and no load connected. With a 75W ac load (incandescent light bulb) dc input is 7.1A at 24v. Thus, inverter is always pulling 96W to run itself. Running continuously this will dissipate 2.3 KWh in 24 hours, about the equivalent to the output of two 250W panels on a sunny day.
A good work-around is to power small loads such as lighting circuits with a high efficiency inverter such as OPS4024NC, which is on all the time, and wire high-power inductive loads to the APC6024D.

https://www.sigineer.com/product/6000-watt-24-volt-to-120240-vac-split-phase-inverter-charger-pure-sine-wave/
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Online NiHaoMike

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Re: Running power tools like mitre saw off an inverter
« Reply #2 on: May 22, 2019, 08:30:00 am »
You'll want V/Hz scaling for motor loads, to greatly cut down on the inrush. That usually comes at a huge price premium, but you could just get a well built modified sine inverter and run a VFD from it.

Another trick, if the motor is to be started with next to no load, is to connect a hair dryer in series and bypass that once the motor is up to speed. Hard to beat the low cost for something like a saw, but that won't work on anything with a substantial starting torque like compressors.
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Online Circlotron

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Re: Running power tools like mitre saw off an inverter
« Reply #3 on: May 22, 2019, 09:18:03 am »
>It depends on the inverter. This Sigineer APC6024D 6KW inverter is rated for an 18KW surge for 20s. This is a ferroresonant transformer based unit that weights roughly 80 lbs and is extremely rugged..... One downside to this for solar applications, which is a problem with most all transformer based units, is high no load power draw. The unit draws 96W at 24v input, (4A dc input) with the inverter running and no load connected.
I'd say most of the problem is the losses in the ferroresonant transformer. I once worked at a place where we made them and there was this 2KVA one just sitting there that nobody wanted. After seeing if I could take it home I checked the no load power draw. It was either 200W or 400W, can't remember now, 1989. Anyway, that put an end to that idea. Those transformers run quite hot and part of the core is in saturation so the losses would be relatively high. An inverter with a normal transformer shouldn't be nearly so bad.
 

Online Circlotron

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Re: Running power tools like mitre saw off an inverter
« Reply #4 on: May 22, 2019, 09:20:42 am »
How hard is it to run big tools like that off an inverter,... I would be getting pure sine.
If your tools have brush motors there is probably no need for sine wave. They should run on anything you throw at them, including DC. For induction motor, yeah, sine is better.
 

Offline Red Squirrel

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Re: Running power tools like mitre saw off an inverter
« Reply #5 on: May 22, 2019, 01:02:34 pm »
Yeah rather stick to sine as I don't want to be limited by what I can run, ex: some motors like it some don't, easier to just get sine and not worry.  But modified sine ones can be quite cheap and beefy for same price...   so it is an option.  Most of the permanent loads will be lighting anyway which won't care about modified sine.

I was looking at this inverter:

https://www.amazon.ca/gp/product/B00AYH6AK8

One review does say it runs a 15 amp mitre saw so that is promissing.    Using mitre saw as example here as it's probably one of the more aggressive normal tools when it comes to startup load, maybe compressor would be a bit worse.   I'd probably be running that and a circular saw.  Maybe weed whacker, but probably upgrade to a battery one.

Low 1k range is as high as I want to go though, I would be splurging more if this was for an off grid cabin/house and going with the ferroresonant one though and ideally a redundant setup.  One thing I've kinda gave some thought for off grid is that I could probably run a bunch of "grid tie" ones too to add redundancy and extra power.  At least I think that would work.  As long as the main one is running.

The blow dryer idea sounds interesting too for the saw... maybe I can just modify my saw and add a load coil with a switch to turn it on and then off to start the cut.  Or I could build a separate device that it plugs into, that might be a better bet as it will be more universal.

Basically this is more for an experiment, I want to see if I can build my deck with just solar.  I think it can be done as long as I get a good inverter.    But even after this project is done then I'll probably add various solar circuits throughout the house so be nice to be able to run big loads if I choose to.  The solar system is only 400w so obviously I'm not going to run big loads for a long time, but like in an emergency I could probably still run the microwave or something for a few minutes.
 

Offline dirtcooker

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Re: Running power tools like mitre saw off an inverter
« Reply #6 on: May 22, 2019, 11:25:14 pm »
>An inverter with a normal transformer shouldn't be nearly so bad.
I have yet to find a decent inverter with idle power under 50W. 60 hz transformer based units typically use ferroresonant transformers which provides good voltage regulation and protection for the output mosfets. There is a trade-off in the design of these transformers, efficiency vs saturation vs idle power. The manufacturer usually goes for decent efficiency under full load, which results in high idle power.
The so-called "transformerless" designs convert power at high switching freq, like 100 khz, instead of 60 hz. They are much lighter, more efficient, have lower idle power, but are not very robust. I've cooked out plenty of them running power tools and such. As a result, off-grid people avoid them like the plague. Voltage regulation isn't very good. For example, I bought one of these Aimscorp units: https://www.amazon.com/gp/product/B007Q2YRE0 which is a piece of garbage but it does run lights. It is rated at 5KW but will not run a 1 KW microwave. Output voltage regulation is horrible. I posted a review of it on Amazon.
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Offline dirtcooker

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Re: Running power tools like mitre saw off an inverter
« Reply #7 on: May 22, 2019, 11:37:33 pm »
The Sigineer APC6024D will run power tools such as circular saws with no problem.
I just purchased a Sigineer PSI3024NC https://www.sigineer.com/product/3000-watt-24v-to-100v-110v-120v-pure-sine-wave-high-freq-power-inverter/ but haven't had a chance to test it. Idle consumption is specified as < 1A, so we'll see. It is a high frequency design so likely will not be robust as the APC6024D. One possibility is to run power tools and inductive loads thru a ferroresont transformer connected to it.
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Offline Red Squirrel

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Re: Running power tools like mitre saw off an inverter
« Reply #8 on: May 23, 2019, 08:33:33 am »
Not finding that one in Canada, though since it looks like it's based in China and not US I wonder if I could safely order that without getting hit with customs...

I might take my chances with the Samlex one I linked to though and if it does not run the tools I want maybe I can just do the blow dryer idea of putting one in series, but instead of a blow dryer I'll just make a box that uses nichrome wire (can experiment with different resistences) and a relay that closes to bypass it once it's up to speed.  Might even be able to automate it by having it detect current.  Zero current = keep wire in series, current = wait a few seconds then bypass.  Would be a simple way to go about it.   

Suppose buying an actual feroresonant transformer would be an option too?  Plug transformer in the outlet I want to use, plug tool in transformer.   What about a standard transformer?  Those are easier to find.    I figure since I won't be running stuff like this THAT often it probably makes sense to concentrate on having the power output capacity with low idle, and just deal with the bigger loads on a case per case basis.
 

Offline dirtcooker

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Re: Running power tools like mitre saw off an inverter
« Reply #9 on: May 24, 2019, 01:22:44 am »
The Samlex is probably a rebranded chinese make of some kind, marked way up. Sigineer commercial invoice had value at $120, so even if you had to pay duties (I didn't pay any but am in US) it will still be far cheaper.
A hair dryer or resistance in series with the saw is not going to work very well. The saw will be slow to start, or not start at all. A standard non-saturated transformer won't regulate voltage or protect mostfets nearly as well as the magical ferroresonant type.
By the way, you should ask Samlex what the idle current draw is before you buy it.
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Offline dirtcooker

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Re: Running power tools like mitre saw off an inverter
« Reply #10 on: May 24, 2019, 01:28:06 am »
harbor freight has cheap multi KW chinese inverters for a couple hundred bucks, and you can take it back after it burns out (for 90 days, according to the checkout cashier - I just bought a 12v 1KW Jupiter branded inverter).
« Last Edit: May 31, 2019, 09:40:09 am by dirtcooker »
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Offline Seekonk

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Re: Running power tools like mitre saw off an inverter
« Reply #11 on: May 24, 2019, 04:01:38 am »
Here is a little trick.  I have a 400W gas generator that will be killed by a chop saw or a vacuum.  I took an old UPS transformer and made an auto transformer out of it so it would produce about 100V.  That allowed me to run the vacuum or miter saw at reduced load. That should help out a lot of small inverters.
 

Offline Red Squirrel

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Re: Running power tools like mitre saw off an inverter
« Reply #12 on: May 24, 2019, 05:44:51 am »
No Harbor Freight here, I think that's an American thing.  There's Canadian Tire but they only have a 1000w model in pure sine.

There's an electrical distributor here though I sometimes go to for thick wire and other things I can't get at the hardware store, you can't really shop around, it's more of a desk to ask what you need but suppose I can check what they have and recommend.  Last time I was there they had solar related stuff.     I'm willing to pay 1k for something that will work but don't want to overpay either so if that Samlex is just a rebrand then won't go with that.

Suppose the Sigineer is worth checking out though.  I've just been hit hard with duties before, sometimes it ends up being 3x the price of the item.  It's very randomized.  But since it's from China like most stuff from Amazon and Ebay which I never pay duties for, I'm thinking I might be safe...
 

Online NiHaoMike

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Re: Running power tools like mitre saw off an inverter
« Reply #13 on: May 24, 2019, 05:51:21 am »
Have you priced a VFD plus a modified sine inverter? Might be cheaper and will definitely give you the V/Hz scaling for motor loads.
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Offline Red Squirrel

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Re: Running power tools like mitre saw off an inverter
« Reply #14 on: May 24, 2019, 06:37:58 am »
Hoping to keep this simple enough, just a single 120v solar powered source that I can plug anything I would normally plug in a household outlet, basically.  I want to eventually have outlets throughout the house too.

Though if it's not possible to keep it that simple then I could maybe do a separate VFD or soft start  that just plugs in and has power outlets out, for the few loads I might want to run when I need to.
 

Offline dirtcooker

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Re: Running power tools like mitre saw off an inverter
« Reply #15 on: May 31, 2019, 09:44:34 am »
The Sigineer APC6024D will run power tools such as circular saws with no problem.
I just purchased a Sigineer PSI3024NC https://www.sigineer.com/product/3000-watt-24v-to-100v-110v-120v-pure-sine-wave-high-freq-power-inverter/ but haven't had a chance to test it. Idle consumption is specified as < 1A, so we'll see. It is a high frequency design so likely will not be robust as the APC6024D. One possibility is to run power tools and inductive loads thru a ferroresont transformer connected to it.
I just did some preliminary tests on the Sigineer PSI3024NC 3000W sinewave inverter: With no load the inverter draws 0.96a at 25v = 24W. It runs a 1200W microwave oven no problem, pulling 74.1A * 23.6v = 1749W from the battery, outputing 114vac *14.9A rms = 1699W while heating a cup of water. I can run a circular saw without any problems so far, which draws about 10A at 115 vac (not cutting anything). The inverter is connected to a bank of 4 Rolls Surette S-550 batteries in series with 4/0 welding cable.
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Offline Red Squirrel

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Re: Running power tools like mitre saw off an inverter
« Reply #16 on: June 09, 2019, 01:21:16 pm »
Was poking around Amazon some more and found this one:

https://www.amazon.ca/GIANDEL-Inverter-Outlets-Control-Display/dp/B07D1LRKY5/ref=cm_cr_arp_d_product_top?ie=UTF8

Is that a reputable brand? It's Australian, so wonder if anyone is familiar and can vouch for it. I imagine it will have some sort of certification or at least be legal to use in Australia.  Ex: it's not a brand that's just straight from China.

I might just buy that Sigineer though I'm just worried about how much more it will end up costing once I factor in exchange rate and any customs.  It's kind of a gamble.  I could order it and take my chances and if customs ends up being too much I can return it, can you do that?

Another thing, Canadian Tire has a huge sale now, like 50% off lot of stuff.  There's a 3000w 12v inverter that is going for like $300ish.  I might chance that.  It's not pure sine though, but at that price, I might just do it.   3000w at 12v is a crazy amount of amps, but evne if I size my system for 100 amps DC max at least I have that extra buffer.  Things like a mitre saw don't need to run for a very long time so even if it goes over the fuse rating for a bit I think I will be fine.

I think the mitre saw and most power tools use brushed motors anyway, so I think for most loads I'll be fine.  I don't know about microwave though, but that's more of a "nice thing" I don't have immediate plans to try to run one. 
« Last Edit: June 09, 2019, 01:30:32 pm by Red Squirrel »
 


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