Forums : Markon 15Kva 3Phase generator

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Markon 15Kva 3Phase generator


Sun Feb 25, 2007 11:39 pm
Hopefully, this is the site I have been looking for and you may be able to help me. I have the above alternator and a 4 cyl Lister engine that runs at 1500 rpm. I need to wire the alternator to obviously produce power but at 240 volts to run part of my house as we live in the sticks and every time its windy the power goes out. Firstly, if I take a single phase from a 3 phase 15Kva alternator, what sort of power output in Kw would I be down to? The alternator can take a second set of windings aparrently and double its output if i needed. Does this sound feasible? In a box on top of the alternator there is the 3 phases labeled 1 2 and 3 and a N .
Do I just take the power off 2 of the lives and will this unbalance the alternator? I know this is a lot of questions but I need to learn a lot if I'm going to get this done. I can send pics if it helps. Many Thanks, Graham.


Sun Mar 11, 2007 12:32 am
A three phase 15kw generator produces 5kw per phase.
This is slightly different, however, than 15kva. Deceptive marketers tend to rate products by va (volt-amps) instead of watts because you get a bigger number that way. Watts = Volts x Amps, but va uses peak instead of RMS voltage. You see this often when purchasing an Uninterruptible Power Supply (UPS) for a computer. One rated at 300va is only 212 Watts because they use peak voltage instead of RMS voltage for their “measurement ”. RMS is 0.707 of peak when dealing with a sign wave.
I would have to wonder if the generator only produces 0.707 of 15,000 — which would be 10.6kw! Or 3.5kw per phase!
Of course, I may just be over-reacting to your choice of words...
Anyway, using only one or two of the phases would not “unbalance ” the alternator — you simply would not get full output rating. Keep in mind that you also do NOT have 240v for running major appliances.
The only way to fully utilize the output of the generator would be to wire three independant circuits (or loads, however you wish to say it) to the generator. Since most homes do not have a way to do this, I suppose you could just install three 120v outlets. A duplex outlet correctly wired can handle 20amps per socket. You'd have six outlets at 20amps or 14.4kw available. You'd also have a LOT of extension cords running around!
As far as a second set of windings goes, they are usually wired in series to give 240v/416v or parallel to give 120v/208v.
If you truly want 120/240vac residential split-phase power, you can re-wire the generator in a similar fashion to the way I did. You would have about 10kw output and should protect the generator with a 40amp inline breaker. You need to dig further back in the wiring to find where the wire labled "N" breaks into three separate wires. Depending on the rig, this may be INSIDE the generator head. The last person I discussed this with had the wiring on the rotor.
Edited Sun Mar 11, 2007 12:51 am by AnOldMan


Sun Mar 11, 2007 12:38 am
Oh, one other thing.
If your generator is running at 1500rpm you are likely producing only 50-cycle electricity. (50hz) 50-cycle is used in Europe, 60-cycle is used in the USA.
To get 60hz you would likely have to run it at 1800rpm.