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Generating 110v 15 Amps From Farm Tractor

03/23/2017 10:47 AM

I installed a 1500 watt modified sine wave inverter to run an 8 amp, 110v chainsaw on my ancient MF 130 tractor. It worked very well. During a recent power outage I tried to run a !500 watt microwave and did not work. I thought that the old generator was not capable of the 125 amps required. I thought to replace the generator with a 150 amp alternator. I thought an alternator with a built in regulator and a single wire output would simplify my task. Am I on the right track or is there a better way?

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#1

Re: generating 110v 15amps from farm tractor

03/23/2017 11:09 AM

Ahem - <...125 amps...> - shouldn't that be 13.64 amps for <...!500 watt...> at <...110v...>?

<...did not work...> The poor thing was almost certainly overloaded, and probably shut itself down to protect itself using internal overload protection circuitry.

<...is there a better way?...> Either a smaller microwave, or use the engine itself as the cooker with an intervening frying pan, would both work, as would a small campfire made of the material that the chainsaw has felled.

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#3
In reply to #1

Re: generating 110v 15amps from farm tractor

03/23/2017 11:35 AM

Presumably he's talking about the 125A @ 12Vdc required from the generator for input to the inverter.

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#4
In reply to #3

Re: generating 110v 15amps from farm tractor

03/23/2017 11:39 AM

Who knows?

<unsubscribes>

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#2

Re: generating 110v 15amps from farm tractor

03/23/2017 11:33 AM

You are barking the wrong tree, or barking up the wrong tree. Hard to see from here.

Generally speaking, the alternator provides about 13.4-13.8 volts at sufficient amperage to keep on board battery charged. The output from the battery is input to a power inverter. Usually, you want beefy wires from battery to inverter connection.

Your 1500 W inverter might only be 1425-1450 actual DC Watts. Your microwave states 1500 W, supposedly at 100% full power. Have you attempted operating the microwave at a lower power setting (if adjustable by control panel)?

Other than that, cook on wood.

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#15
In reply to #2

Re: generating 110v 15amps from farm tractor

03/24/2017 8:20 AM

Wouldn't work with any microwave that I have ever owned because reduced power cycles the MW on and off at full power.

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#5

Re: generating 110v 15amps from farm tractor

03/23/2017 12:18 PM

The issue could very well be the modified sine wave inverter. The microwave may not convert that energy very well as it drives the magnetron. The high voltage transformer will not be as efficient with the modified-sine wave because of the additional harmonics. All indications from people's experience posted on the Internet is that a MSW inverter should power a microwave oven OK, but you may need a slightly higher rated inverter to drive the oven.

Does it not work at all, i.e. no display or does it trip off when starting the cook cycle?

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#6

Re: generating 110v 15amps from farm tractor

03/23/2017 1:08 PM

Yes it would work for you with a few minor/ish changes. I would recomend a common 140 - 160 amp one wire commercial unit for a new alternator.

I have been updating our older larger diesel farm tractors to them over the last few years and they are pretty easy to work with and take continuous high current loading without any issue unlike most suposedly equivalent current rated automotive units that can only handle that level of output at high RPMs for a short time.

These are the ones I have been using are Delco 22si style and cost around $180 at Napa. Delco 22si Heavy Duty 145 amp alternator The actual as built and tested specs sheet show they will put out quite a bit more than 145 amps and will do it at the RPM range a tractor engine can handle!

Now as for your old MF 130 I have a MF 202 industrial forklift which is based on the larger but very similar 135 tractors so that gives me a fair reference to what you have to work with being I did convert mine over the a 100 amp delco 12si alternator when I got it and all new wiring as well. (The old generator was worn out high priced junk.)

You will need to make different and larger brackets to adapt the alternator to the old generator location plus change out the stock ~10 ga generator feed wire going to the battery with a 1 - 2ga as well that bypasses the ammeter (if you have one) unless you can find a 150 - 200 amp rated one.

You will also have to upsize the old generator drive belt to a larger one if possible. If yours is like mine was it has a 1/2" V belt but a 5/8" works but it will sit a bit higher in the crankshaft and fan pulleys.

Also, if yours has a tachometer that ran off the back of the old generator that won't work anymore being the alternator don't have a mechanical tach drive point off the back side.

Lastly I would recomend fitting the largest deep cycle battery you can fit in your tractor as well. My 202 will fit a group 31 but its tight and I had to modify the battery tray a bit to get it to sit low enough. I'm Not sure what a MF 130 can fit so do some measuring and battery case dimension comparison research if you go bigger.

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#22
In reply to #6

Re: generating 110v 15amps from farm tractor

03/25/2017 10:29 AM

Thanks tcmtech, nothing like having someone how has done it! I noticed that the Delco alternator you have been using is a 3 wire type. How does the wiring work on that? Fair amount of space for the larger battery. Should work.

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#24
In reply to #22

Re: generating 110v 15amps from farm tractor

03/25/2017 4:25 PM

As far as I know they work either way. The ones I have came with a plug on the side port where the extra two control wires went that can come out if the machine its going on need to use them for any reason.

If you're not sure about it when buying one just ask them specifically for the 1 wire version. Odds are it's the same one I linked to.

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#7

Re: Generating 110v 15 Amps From Farm Tractor

03/23/2017 1:15 PM

The alternator is used to charge the battery, it's the battery rating you need....the amp hour rating...a 100ah battery should operate a 1500 watt microwave for about 20 min if the battery is fully charged....also the wire size and length of run are both critical, they must be able to carry the load...check this calculator and you can see the length of run of the 12v wire changes the wire requirement dramatically...for a 100 amp load(min) and a 3' run you need #2 awg for 6' you need #00....so the shortest run possible to the inverter from the battery is recommended...now from the inverter to the microwave is only about 13 amps@ 120v and much smaller #14 awg can probably suffice...

http://www.solar-wind.co.uk/cable-sizing-DC-cables.html

http://www.donrowe.com/power-inverter-faq-a/258.htm

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#8

Re: Generating 110v 15 Amps From Farm Tractor

03/23/2017 3:30 PM

You'll need more than 1500W in to get 1500W out - how much more will depend on the efficiency of the inverter.

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#9

Re: Generating 110v 15 Amps From Farm Tractor

03/23/2017 5:14 PM

Another highly likely scenario is that when you use your chainsaw powered by the tractor, the tractor is right there with you, as in near the chain saw. When you attempted to use the microwave, it was likely in the kitchen, whereas I doubt that you drove your tractor into the kitchen, so you used an extension cord. The microwave was going to draw the PEAK power of that inverter, so ANY voltage drop from the tractor to the kitchen on that extension cord was going to likely take the microwave out of commission. And the voltage drop would be made SUBSTANTIALLY WORSE if that extension cord was less than 12ga wire.

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#14
In reply to #9

Re: Generating 110v 15 Amps From Farm Tractor

03/23/2017 11:37 PM

Actually a 1500 watt load on a 100 foot 14 gauge copper extension cord would only see about 6 volts drop from one end to the other.

At ~2.5 ohms per 1000 feet a 100 foot 14 gauge cord would have a total resistance of ~.5 ohms which for a 1500 watt load at 120 VAC that's a miserly ~ 6.25 volts loss which is only about 5% less than ideal and still well above the typical +- 10% of nominal rated voltage any properly designed appliance is supposed to work with.

Which BTW my old 1500 watt (VA actually) microwave is rated for a 115 VAC input not 120 VAC so at ~ 114 VAC it would be working near optimally and not actually operating a slightly overdriven condition.

The way I see it at worse even with a bit of under voltage and the square wave input he will still get his Hungry Man microwave dinner cooked. It just might take him 7 minutes instead of 6 but in the end he will live and the cat won't end up on the BBQ for him to do it!

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#10

Re: Generating 110v 15 Amps From Farm Tractor

03/23/2017 6:29 PM

Try running the microwave at 50% or less. This will determine if the modified sine wave output is the issue. If it works, then gradually increase the power level until it fails. Then you can determine what you want to do.

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#11
In reply to #10

Re: Generating 110v 15 Amps From Farm Tractor

03/23/2017 7:47 PM

Depends on the device operation. Don't know about newer models, but with old ones (like my clockwork one) the heating control just sets the mark/space ratio for the ON time - e.g. 50% would be 10 sec on/10 sec off (repeated).

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#12
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Re: Generating 110v 15 Amps From Farm Tractor

03/23/2017 10:38 PM

Even the newer microwaves that I have seen reduce power by varying the duty cycle exactly like you said.

Come to think of it, it's not a power reduction, it is a reduction in the energy delivered. Unless of course you were to specify average power

But the average consumer won't understand 50% energy delivered either.

Never mind.

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#13
In reply to #12

Re: Generating 110v 15 Amps From Farm Tractor

03/23/2017 10:54 PM

Mine is the same way the power setting just reduces the time it's on and off according to the timer....for instance if you put it on 30% power it's on for 3 seconds and off for 7 sec, then just repeats that pattern until the timer runs its course....

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#16

Re: Generating 110v 15 Amps From Farm Tractor

03/24/2017 5:22 PM

Disregard post 10, sorry about that.

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#17

Re: Generating 110v 15 Amps From Farm Tractor

03/24/2017 5:23 PM

Disregard post 10, sorry about that.

Can you borrow a lower power microwave for testing?

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#18

Re: Generating 110v 15 Amps From Farm Tractor

03/24/2017 6:57 PM

Is that 1500w the input or output power?

Microwaves are generally rated at output power, so your 1500w microwave will likely be drawing up to 50% more than that from the inverter.

Microwaves also have pretty poor power factor which makes them an even more difficult device for an inverter.

A 1500w microwave could easily draw in excess of 200 amps from a 12v DC supply, and maybe even more using a modified square wave inverter, no such thing as a modified sine wave inverter, they produce a square wave that is then modified to form shoulders.

All of the above means that neither your inverter nor your DC supply are sufficient in capacity to run said microwave. Running on low setting won't help either as a microwave controls its power by duty cycle, ie. as the settings are reduced, it still draws full amps when the Magnetron is energised, it's just energised for progressively shorter time periods

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#19
In reply to #18

Re: Generating 110v 15 Amps From Farm Tractor

03/24/2017 8:34 PM

If he's in the US he's limited to 1500 watts or 1500 VA input on a 120 volt line that isn't hard wired in or uses a special service capacity plug which very few kitchen appliances do.

~83% of what a standard residential 15 amp circuit can handle by national code.

That and most every appliance manufacture inte US rates their products by input watts as well so if his says 1500 watts that's 1500 watts input even if the magnetron only puts out half that.

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#20
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Re: Generating 110v 15 Amps From Farm Tractor

03/24/2017 11:29 PM

Thank you for that info.

Over here we can plug up to 2400w into a standard GPO, and then 3600w into a 15 amp rated one or 4800w into a 20 amp rated one, all of which have a similar configuration but with differing dimensioned pins to prevent the higher rated devices being used on the lower rated outlets although you can go vice versa.

Many of our 30 amp plus ovens and hotplates are now plugged into 15 or 20 amp outlets, relying on diversity calculations for loading.

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#21
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Re: Generating 110v 15 Amps From Farm Tractor

03/25/2017 10:01 AM

Yea. Many years ago a lot of higher capacity devices were designed around 20 amp circuit capacities and came with 20 amp plugs on them and ratings up to 1800 - 2000 watts input but unfortunately too many people either bent the prongs to fit 15 amp sockets or put cheater adapters on the plugs or just replaced the plugs with 15 amp ones then tried to run them off 15 amp circuits.

Either they didn't work right due to constantly blowing fuses or tripping the breakers or people just switched out their 15 amp fuses and breakers with 20's even though their homes only had 14 ga wiring which started burning too many places down from it.

As of now finding any modern appliance or power tools with a more than 1500 watt input ratings and a factory equipped 20 amp plug on it cord is near impossible unless it's designed for a commercial application where it guaranteed that it will have a properly sized and designed electrical feed supplying it.

Now most everything in a residential application now that draws above 1500 watts on 120 volt power is expected to have dedicated hard wiring supplying it or just be 240 volt powered.

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#23
In reply to #18

Re: Generating 110v 15 Amps From Farm Tractor

03/25/2017 10:45 AM

This will be interesting. The microwave I'm using is a Panasonic Inverter. It's claim to fame is that it actually delivers continuous energy at a lower output rather than switching on and off. I'll test it!

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