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Old 02-10-2012, 09:38   #16
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Re: I need Generator Help

Ok, that makes sense.

So as is always true, nothing is free, and it's not really a 4kw generator anymore in the traditional sense.
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Old 02-10-2012, 09:58   #17
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Re: I need Generator Help

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Originally Posted by Dsanduril View Post
Yes/no/maybe. Depends on how the center-tap is constructed.

Dual-winding style connection:


True center-tapped connection:


Delivered in Europe connections to U1 and U2 would be provided and you get 230V and full generator power. In the dual-winding case U3 is jumpered internally to U4, in the true center-tap case the center tap is just capped off and not available.

Delivered in the US the center-tap case gives you half power between U1 and the center-tap and another half-power circuit between U2 and the center-tap. The center-tap is used as neutral. You get full power from the generator, but the maximum power per circuit is one-half total output (which means if you have a 3kW generator running a single 2.5kW load it just won't fly)

In the dual-winding case you can connect U3-U4 as in Europe and get a 120V/240V dual voltage unit (by connecting your load to U1 and U2 you get 240V, by connecting to U1 and U3/U4 or U2 to U3/U4 you get 120V at half-power). You can also connect U1-U4 and U2-U3 and get a single full power 120V circuit.

The "dual-winding" doesn't have to denote two physically separate windings (in a small generator it generally doesn't, in a large it may), just a break in the winding where the tap(s) come out. IME I see lots of generator heads with the "dual-winding" tap because it really doesn't cost much to build it that way, and allows the most flexibility in distribution.
Very interesting and educational! Thanks for that.
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Old 02-10-2012, 10:21   #18
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Re: I need Generator Help

From an electrical perspective I suspect the US is more used to these cases. 90+% of household electricity in the US is delivered from the utility as 240V center-tapped. I know that's not what the guidebooks say, but the reality is that the utility delivers 240 (older installations 208), we ground the middle and have two out-of-phase 120V circuits. If you want a 240V circuit (many houses use them for cookers, clothes dryers) you use the two ungrounded legs.

A whole different approach from that used in Europe, but one that is very familiar here (to electricians). A case-in-point, my mother-in-law just purchased an antique (sort-of) cabinet from England, when it was delivered she found a 240V lighting circuit, which caused quite a tizzy. Americans all think in terms of 120V, but in reality US electrical power is 240V and all I had to do was wire her a 240V receptacle for the cabinet (incandescent lighting, it is pretty frequency agnostic).

When it comes to generators, many here are sold as 120/240V with the same center tap and are the same units sold everywhere else in the world. The two things that throw a spanner in whole works are the 50Hz vs. 60Hz and the grounding (US would ground the center tap, Europe would ground the neutral end tap). When doing a conversion you do have to be careful to see if anything is grounded, portable generators are usually easy to figure out, fixed mount generators that are intended to be tied-in as backup systems can be more difficult.
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Old 02-10-2012, 10:39   #19
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Re: I need Generator Help

However, I may be wrong. But isn't european 220V above earth? and us 220V is 110V above and 110V below, combined to give 220V peak to peak?
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Old 02-10-2012, 11:03   #20
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Re: I need Generator Help

Quote:
However, I may be wrong. But isn't european 220V above earth? and us 220V is 110V above and 110V below, combined to give 220V peak to peak?
In essence, yes. Europe grounds one end of the 220V, the US grounds the middle. When you run a 220V device in Europe one leg is (typically) grounded, when you run same device in the US it is not grounded and the only connection to ground is the safety ground conductor.

In the generator case a generator delivered in the US would commonly have the center tap attached to the frame and used as a ground, in Europe it would be one of the end taps. Sometimes finding that connection can be the hardest part (from experience)
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Old 02-10-2012, 12:49   #21
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Re: I need Generator Help

A question that I have is if I check the voltage comming out of the outlet on the generator, will I have 240V in 2 of the plugs and one of the plugs ground? Also how does one determine what Hz are being delivered?
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Old 02-10-2012, 13:04   #22
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Re: I need Generator Help

I believe European 240V with three wires you will have one hot wire, one neutral wire, one safety/ground wire. The output is 240 V between the hot and the neutral wire. I'm guessing you would probably read 240V from the hot to the safety as well but of course you aren't supposed to use that as part of the circuit.
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Old 02-10-2012, 13:06   #23
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Re: I need Generator Help

How do you measure Hz?
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Old 02-10-2012, 13:10   #24
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Re: I need Generator Help

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How do you measure Hz?
it is that thing that makes you jump 50 or 60 times a second if you stick you fingers in the plug,count the jumps
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Old 02-10-2012, 13:11   #25
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Re: I need Generator Help

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How do you measure Hz?
Oh yes, forgot to add that. Need some sort of frequency counter. Many voltmeters these days will include a frequency setting.
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Old 02-10-2012, 13:19   #26
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Re: I need Generator Help

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Thanks to everyone for your help, I have looked at the Gen set a little closer and the power plug in has 3 wires going to it, a Blue, a Brown and a White/Green wire.
Rocketman,

In European wiring Brown is the hot wire, Blue is the neutral wire, and Green is the safety ground. You should have 240V measured from Brown to Blue. You will probably also have 240V from Brown to Green and 0V from Blue to Green. The latter will depend on whether the neutral and the ground are bonded together.

Most multi-meters don't measure frequency, you either have to get one that does or get a simple analog meter (E-Bay Freq. Meter) that you can connect. Or you could drag out an oscilliscope For long term use having the panel mount meter connected is handy, it can alert you to conditions when the generator speed is dropping below the setpoint (due to overload or to other things).

[Edit] Sorry, but the meter I posted the link to is rated at 100V, didn't catch that before. But you get the idea[/Edit]
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Old 02-10-2012, 14:36   #27
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Re: I need Generator Help

Everyone has been very helpfull, thanks a lot.
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Old 15-10-2012, 19:26   #28
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Re: I need Generator Help

I hope someone can help with this question, I have removed the generator from the encloser, and taken a pic, it has four wires comming out of one side of the windings and 2 wires comming from the other side. The 4 wires on the left are blue, white, and 2 red wires. The 2 wires coming from the Right are off white and they connect to white cylinder. The wires on the left, the white one turns into brown after a spice, the blue one stays blue, I believe it is nutral, but the 2 red wires are not used. Could these wire be used as 110V?
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Old 15-10-2012, 20:03   #29
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Re: I need Generator Help

A couple of questions:

1. The two red wires that are "not used"; are they joined together or capped off separately?

2. The two off-white wires that are connected to the cylinder; do they connect to one point (i.e. are they common) or do they have different connections?

3. Is the cylinder a large capacitor? Picture if you're not sure.

If the red wires are joined together and not used then I would suspect this is a center tap and you should be able to get 120V from Blue to Red and another 120V from Red to Brown (white before the splice). Only guessing though. If the red wires are not joined together then not so comfortable with a remote diagnosis.
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Old 15-10-2012, 20:31   #30
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Re: I need Generator Help

A couple more diagnostics.

1. Measure the resistance between the Blue and the Brown wire. At a guess it will be in the single digits of Ohms.

2. Measure the resistance between the Blue and the Red and between the Brown and the Red. Is it about one-half the first resistance? That would be a pretty good indication of a center tap.

3. If the Reds are joined together then separate them. Now measure between Blue and each Red. One should show open, the other should match the previous reading. Same for Brown to Red.

Report back.
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