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I just couldn't pass up buying a 6KVA Wahoo generator for $500. I know you get what you pay for but I like to tinker with stuff, it's a Honda replica...to an extent. It only has two 120 volt outlets (25 amps each) and a 50 amp circuit breaker.
Can someone direct me to information to add a 240VAC circuit?
I bought this as a learning project as much as anything.
thanks in advance,
Tony
You can get 240V, but you cannot get 240V 2 pole, that is, a sine, cosine wave. What you get is a large sine wave. That would be the difference between single and 2 pole. I personally have no need for a single pole generator which might explain the price difference If it won't run my well pump, it is of no interest to me.
There are, in theory, sevaral ways to get 240 volts with your generator.
The simplest of the practical ones (as practical as it gets) is to buy a transformer with a voltage ratio of two to one, core capacity of at least 6.000 Watts, wire sized on the input to handle 50 amps, and wire on the output side sized to handle 25 amps. This would not be cheap and would be pretty heavy but you could probably design a small trailer to carry it behind the generator. Allied Electronics has one good for 2 KW (you need 6 KW) for $300. Three of those would cost $900 but a single transformer of the right size would be cheaper than three smaler units adding to same capacity.
Another slightly less quality solution is with an auto transformer AKA autoformer. Cheaper solutiom but not by 50%.
Voltage doupler circuit but at these power levels the capacitors are prohibitively expensive and quite large.
You can rewire the stator and rotor. A friend of mine did it with a 4 cyl Perkins diesel powered unit rated about 15 KVA or so.
Etc. etc. blah blah blah.
Short version: If you want a 240 volt generator, buy one.
[img]/forums/images/icons/smile.gif[/img] Pat [img]/forums/images/icons/smile.gif[/img]
Thank you for the input. I will keep it as is....
RaT, Standard residential electrical service (in the US) is delivered as single phase 240 volt with a center tap we call "neutral", i.e. "the white wire." We get our 120 volt circuits by connecting to the center tap and one "leg" (end of the transformer secondary.) Some folks say phase instead of leg but that is not correct as there are not two phases in standard residential power, just two legs with a single phase.
I know you probably know this but I was leveling the playing field for others...
Now the question: Are you saying that your well pump is some kind of polyphase? If so where do you get it? (the polyphase not the pump) Does your electric utility deliver some kind of polyphase to you or do you have to convert from single phase?
[img]/forums/images/icons/smile.gif[/img] Pat [img]/forums/images/icons/smile.gif[/img]
Well Pat, now you got me to thinking. I always thought most folks in the US and I think it was Japan operated on split phase. My understanding was that we had two sine waves and somewhere around the RMS value on each wave we got our 240V. When I wanted to boost from 120V to 240V for a pump motor the transformer salesman said, won't work you need 2 poles. Not wanting to sound stupid since I was puzzled, I left it at that. I have done a few electrical jobs where I need to buck 240V to 120V since there was no neutral but have yet to boost from 120V to 240V. Anyway, I had a 120V generator from Honda that I wanted to do this to to run a small 240V well pump. I gave up and now have a small 120V/240V Honda to do it. I'd like to know though what your thoughts are on boosting 120 to 240 via a boost transformer. The Buck transformers are fairly inexpensive, but the boost transformers are just plain hard to find locally. I am surrounded by PG&E workers and need to get the skinny on what kind of service we have. We have I think 12KV lines that feed typically 25KW transformers that have the 3 taps with the center as neutral which in turn is spliced to the incoming neutral and pole butt wrap for grounding. Most of my experience in electrical is commercial and thus 3 phase and bending conduit. I really like 3 phase, one neutral and 3-120V circuits providing your not running in the Delta configuration. Anyway, I know little about the incoming service since it is a whole different field from being an electrician. Rat...
RaT, Most of my electrical training was in electronics. For a period of time I made my living as an electronic design engineer. To me a BIG wire was something over about 18 to 20 ga. I was more comfortable with miliamps and microamps but I have gotten over it and can, with a pause to think, do fine with residential sized electrical design.
OK residential service... the three output connections on the transformer on the pole (or pad) are both ends of the secondary and the center tap. The center tap is called neutral and measures 120 vac to either end of the xformr. You get 240 across the whole thing. This is simplified version with no consideration for minor taps for boosting or lowering the voltage a bit to compensate for your typical load and your line losses.
There is but ONE PHASE and no hocus pocus with RMS. NO "Y" NO delta just plain ole single phase with a center tap.
I too tried to use a xfmr to boost my 120vac Honda gen to get 240 to run my pump temporarily and failed. Luckily I had found a surplus xfmr and didn't waste a lot of $.
Theoretically if you have enough 120vac and a sufficiently robust xfmr you could run the well pump. If your genny can make a steady 20 amps you could get about 10 amps at 240vac with a simple transformer. For this you don't need a center tap or anything fancy, just a 2:1 xfmr with heavy enough conductors to take the current and enough core in the xfmr to handle the power without saturating and burning up. In reality there is no difference between a step up and a step down xfmr, one is the other turned around. If you can't find one called step up buy one labeled step down. Just ensure it meets the criteria stated above.
I bought a bigger genny with 120 and 240 outlets. I had other uses for it and I didn't "waste time and $ on another xfmr.
Just a few days ago I googled for power xfmrs and there are lots available on the net.
[img]/forums/images/icons/smile.gif[/img] Pat [img]/forums/images/icons/smile.gif[/img]
Thanks Pat, I'll add that to my education. I always wanted to check our electricity at the local college when taking electronics with the scope but the instructor absolutely forbid it. In hindsight, there was no 240V available in the lab so the picture would not have been helpful to my understanding. My education was around the Intel 8080A.
I understand my Honda uses two seperate windings for the 240V part and when you flip the switch to 120 only, you can combine those to get about double the 120 amperage. The largest wire I have worked with is 1000 MCM copper. It all had to be pulled out and replaced with triple parallel runs of 750 MCM ALU. I got to keep the few thousand feet of copper wire. I have one foot left, the rest I turned in. [img]/forums/images/icons/smirk.gif[/img]
RaT, People do "funny" things with test equipment. I loaned out a VTVM (with a "lighthouse" tube type diode in the probe that allowed it to detect up to microwave frequencies and give true RMS readings) to an audio-visual tech who promptly tried to measure the impedance of the electric grid, i.e. he switched it to Ohms and stuck it to 120 VAC. It was full of hand wound precision resistors wound on ceramic cores. When he returned it there were smoke stains out the cooling louvers and lots of ceramic fragments falling out.
In your lab situation, if you had been able to find two wall outlets on different legs you would have had 220-240 vac between the respective hot wires. This assumes single phase power. That is a quick and dirty way to get 240 when there isn't a 240 outlet readily available.
8080 huh? It was an OK chip. The souped up version, i.e. the Z-80 was one of my favorites in the early 80's. the 8086 was OK too but was a real slug compared to the Moto 68000. The 8086 for the non-bitheads reading along was the original 4.77 MHz IBM PC "Brains" and it was a real dog compared to Motorola's 68000 and its linear (non-segmented) address space. Hence the phrase "segments are for worms" a derisive comment directed towards the inferior Intel architecture. Then the reality of the market place and the powerful attraction for those three little letters, IBM overwhelmed reality with marketing and we have seen the progression from 8086 to 80286 to 80386, 80486 to Pentium (marketing name for 80586.)
Oh, sorry, I digress into reverie... My new house is wired for 350 amp service using, I think 500 MCM copper. All I know it is BIG and STIFF and feeds two breaker panels, each with a 200 amp main. A single 400 would have cost $1200-1500 BUT 200 AMP boxes start at about $100 at lowes (with main.)
[img]/forums/images/icons/smile.gif[/img] Pat [img]/forums/images/icons/smile.gif[/img]
I can get Square D 400 amp panels for about $800. The nice thing is how much room there is to have large breakers and big wire. You just need room. I'll be installing a 200 amp myself for our home, we try to go as light on electrical as we can as our utilities price for electricity is not bad, its the transmission and distribution that hammers you. I feed to 100 amp subpanels. Take a picture of your setup and post it in the Farmhouse, I'd like to see it.
PS, I have a 68000 and a 040 sitting in my toolbox yanked out of some old Mac's. I have them to look at.