24kw AC generator frequency problem

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Chris Smith
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Re: 24kw AC generator frequency problem

Post by Chris Smith » Mon Jun 20, 2005 7:07 pm

Shouldn’t it be Sine wave? <p>It looks more like a triangle wave form?<p>Is this a full blown "wound generator" and motor? <p>With a stair case generator a choke/inductor/ coil would smooth it out, BUT?

rshayes
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Re: 24kw AC generator frequency problem

Post by rshayes » Mon Jun 20, 2005 10:21 pm

All of the waveforms appear to be the same fundamental frequency, prosumably 60 Hz. There is a fair amount of distortion, the waveform is not quite a pure sine wave. This may be due to the distribution of the winding in the slots in the stator. A closer approach to a sine wave would probably require that turns from different windings would be placed in the same slot. This would complicate insulating the windings and would be harder to build.<p>Another possible source of the high frequency components might be the slot structure of the stator relative to the pole structure.

Gorgon
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Re: 24kw AC generator frequency problem

Post by Gorgon » Tue Jun 21, 2005 3:25 am

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr>Originally posted by dburlesn:
Well I'll have to think about what to load it with.
Any suggestions?
L1, L2, and neutral
L1 120,
L2 120
L1-L2 240
I intend on wiring an outdoor main breaker panel (Square D) mounted above the generator.
From that I will wire outlets:
240v 50amp Plasma
240v 50amp Stick welder
120v 15amp Grinder
120v 15amp Drill
120v 15amp ????<p>Yes it totals more but like a house not all will be used at the same time.<p>The generator is rated 120vac 208amps, 240vac 104amps.
<hr></blockquote><p>Hi David,
In your calculation you say 120vac 208 amps, This is not correct if you use the generator in 240vac mode. Then you can only take out 104 amps on any 120v winding/outlet.<p>I'm not convinced that asymetrical loading of the 120v windings is very wise either. This may cause you more noise one the output than you and your tools want.(and maybe the generator too.)<p>TOK ;)
Gorgon the Caretaker - Character in a childrens TV-show from 1968. ;)

dburlesn
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Re: 24kw AC generator frequency problem

Post by dburlesn » Tue Jun 21, 2005 4:35 am

Gordon,<p>You are correct.
and that gives me a new question.<p>Home main breakers amp ratings.
If I purchase a "200 amp" main breaker.
Is that 100 amp per leg? 200 total
or 200 per leg?<p>thanks
david

Gorgon
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Re: 24kw AC generator frequency problem

Post by Gorgon » Tue Jun 21, 2005 12:01 pm

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr>Originally posted by dburlesn:

Home main breakers amp ratings.
If I purchase a "200 amp" main breaker.
Is that 100 amp per leg? 200 total
or 200 per leg?
<hr></blockquote><p>Hi David,
The answer on that question depends on how many phases the breaker is made for.<p>A single phase breaker would be '200 amp' total, even if it is a 2 pole breaker.<p>A 3-phase breaker is rated for '200 amps' per leg. <p>At least this is the case here in Norway, and I suppose this is global.<p>TOK ;)
Gorgon the Caretaker - Character in a childrens TV-show from 1968. ;)

dburlesn
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Re: 24kw AC generator frequency problem

Post by dburlesn » Tue Jun 21, 2005 12:10 pm

Thank you, Thank you, Thank you.<p>I assume that 3-phase answer also applies to a Starter, or Contactor?<p>
Thanks<p>David

upsmaster
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Re: 24kw AC generator frequency problem

Post by upsmaster » Tue Jun 21, 2005 2:08 pm

most of the time the number of poles in a genrator determine how smooth the ouuput wave shape is... your gen shows a normal wave shape. i think that the notch that you see at the top and bottom of the sine wave is the excitation supply rectifier turning on at the reverseing of the sine wave as the shaft rotates.... a 200 amp breaker is per pole single double or tripple.
joe

Gorgon
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Re: 24kw AC generator frequency problem

Post by Gorgon » Tue Jun 21, 2005 2:11 pm

As long as it is a 3-phase component, I would say that. Components like this are normally marked with all necessary data and limits.<p>TOK ;)
Gorgon the Caretaker - Character in a childrens TV-show from 1968. ;)

Sterling Martin
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Re: 24kw AC generator frequency problem

Post by Sterling Martin » Tue Jun 21, 2005 3:27 pm

The implication that that a 200 amp. single phase breaker has 100 amp on each pole and adds up to 200 amp. is simply crazy. 200 amp. is 200 amp. per pole for 1 pole or up to a million poles. Also, could you please load the generator? I, like the rest of the people, think that that will make all your problems vanish. Just have a light? Use the light.

dburlesn
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Re: 24kw AC generator frequency problem

Post by dburlesn » Wed Jun 22, 2005 5:05 am

I was out buying a breaker panel, etc. yesterday, and did not get a change to fire it up.<p>Thinking about a load, I need another base board heater for my basement, I think that should be a good resistive load.<p>........ more to come.

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Edd
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Re: 24kw AC generator frequency problem

Post by Edd » Fri Jun 24, 2005 1:38 pm

quote:
If it is just noise fooling my DMM how can I clean it up? <p>1.....I also, am definitely in concurrence on the necessity of in order of an ~ 10% resistive load on the gens output OR the even more resonant /waveform cleaning effect of having an AC motor being on the line as a load (like that bench grinder….3/4 hp…??).
2.....If you had used a full function Freq/EPUT meter in the order of a *Tek, HP, etc, they provide individually adjustable triggering and threshold adjustments to fine tune in to recurrent wave forms.<p>NEVERNOHOWSOMEVER, since you were pressing into use, the somewhat limited additional Freq-meter feature of a DVM, I might suggest the following technique for a current and future refinement of your taking of accurate readings when utilizing the dynamic duo.<p>On the rear of the Tek 465/475, track down the innermost of 3 BNC connectors.It puts out a + gated pulse output that will be in sync with the hoz sweep timebase setting utilized.That will be routed to the DVM signal input while using it in its Freq-meter mode.
Now, looking at your photos / settings of the scope, the observed waveforms that you captured tell us that the interrelational phase relationships of the three winding outputs were all in order and your known taching of the drive speed would have automatically resulted in a 60~ freq output. That is, being with out the additional confirmation of the freq via the scoped observation of a 16.66 ms time duration between waveform nodes. (Since you had the hoz sweep timebase in error by being set off from its cal lock positon.)<p>Using your scope with its precise differentiating triggering capabilities , permits being able to zero in and lock onto the DC-AC component of a waveform anywhere along its +/- slope/level along with low and hi freq components rejection.
A bit more versatile than the afore mentioned * meters , since you are now actually able to see if you are firmly locked onto the waveform.
In order to set up to take a freq reading, all that you have to do is trigger onto the waveform for a lock in and then observe that one cycle of the waveform is displayed across the scopes 10 hoz graticule indexes and then you shift the hoz time base up one click to a higher frequency such that just less than one cycle of waveform is displayed within the 10 graticules of the hoz sweep trace.
E.G..... in your case of using the 2ms hoz time base speed ( PROPERLY LOCKED IN CAL POSITION), and considering that the one cycle of waveform is triggered onto at 0- crossing and then it swings up through its positive node / 0- crossing / negative node and then back to 0- crossing, it would then just have started on its second cycle after 16.66 ms ….soooo it would be necessary to crank the time base freq up to 1 ms sweep speed in order to assure that a second cycle of waveform was not started on within that one hoz sweep trace time period.
Now, you are going to have a coincident, conditioned gate signal output from the scope and feeding into your DVM/Counter to read out the waveforms freq.<p>73's de Edd
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:)<p>[ June 24, 2005: Message edited by: Edd Whatley ]</p>

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