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Old 15-09-2016, 12:15   #16
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Re: Capacitor uf Rating

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Originally Posted by four winds View Post
Without the schematic I just guessing. But I suspect the adjustment the Nexgen rep mentions is to a variable resistor that is in the same circuit to which the capicator belongs.

Altering resistance on a voltage divider network which then affects the charge rate of the cap and consequently the switching of the circuit.

Another guess is that lowering the cap value will increase voltage, not raising.

But I'd tweek the Hz first.


Edit,... BTW, it supplies 30amps at 120volts, correct? Are you sure you are not reaching the borderline of the gens capacity. Falling voltage, falling hz, ........revs dropping? any black smoke?
It's not that type regulator with voltage divider etc.

I looked it up after the Dot guy responded. I found an article that supported what he said above (bottom of page one) about increasing the microfarad rating of the cap to increase voltage.
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Old 15-09-2016, 12:18   #17
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Re: Capacitor uf Rating

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The manual on my generator (not NextGen) calls for a 31.5uf. From the factory it had 35uf in it. When the originals failed, I replaced with 31.5uf. I too found the voltage too low and replaced again with 35uf. I'm now happy.

YMMV
lol.,...... wel that shoots one of my guesses in the foot.

And lends credence to simply ignoring anything I say. Thankfully most people do that anyway.
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Old 15-09-2016, 12:18   #18
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Re: Capacitor uf Rating

Quote:
Originally Posted by four winds View Post
Without the schematic I just guessing. But I suspect the adjustment the Nexgen rep mentions is to a variable resistor that is in the same circuit to which the capicator belongs.

Altering resistance on a voltage divider network which then affects the charge rate of the cap and consequently the switching of the circuit.

Another guess is that lowering the cap value will increase voltage, not raising.

But I'd tweek the Hz first.


Edit,... BTW, it supplies 30amps at 120volts, correct? Are you sure you are not reaching the borderline of the gens capacity. Falling voltage, falling hz, ........revs dropping? any black smoke?
It's not voltage divider circuit. From my manual, not NextGen, but using the same technology - capacitor voltage regulation vs. more exotic AVR.

Quote:
Upon starting, the rotor magnetism (residual magnetism of the nucleus) induces a voltage in the auxiliary excitation windings. This voltage is applied to the capacitors and makes a capacitive current circulate in the closed circuit composed of the capacitor and the auxiliary winding. This current produces a magnetic field which strengthens the rotor magnetism generating a voltage inside it which, rectified by the diodes, makes a continuous current circulate in the rotor field windings. The rotating magnetic field due to circulation of this current in its turn generates in the primary winding the rated voltage to the generator terminals.
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Old 15-09-2016, 12:23   #19
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Re: Capacitor uf Rating

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Originally Posted by thomm225 View Post
It's not that type regulator with voltage divider etc.

I looked it up after the Dot guy responded. I found an article that supported what he said above (bottom of page one) about increasing the microfarad rating of the cap to increase voltage.
thanks Thomm for the feedback. I'm data throttled again so didn't try to find specific information. Just curious how this setup works as with most things electronic.

Obviously will keep my ill informed opinions to myself. And try to learn something.
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Old 15-09-2016, 12:25   #20
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Re: Capacitor uf Rating

I'm at 62 hz no load, and 60 under 21 or so amps, my normal load, but it does sag to 58 or so under heavy load, approaching the engine limit, no smoke, but you can tell she is about maxed out, you can hear it labor. She will make 30 amps, but just barely and I wouldn't keep it there, now if I do the boats 30 amp breaker will pop, so in truth the gen and boats electrical system are pretty well matched. Of course as voltage drops, amps go up, so 34 amps at 105 voltage is the same power as 30 at 120, so the voltage sag will drive my amps over limit.
What happens though as the RPM drops just a little voltage sags to 105 or so and I know long term that is not good for my electric motors and who knows what all else, they are designed I believe to operate on 120, average residential power is approaching 125.
I will crank up the RPM if I have to, I'd rather if possible leave the hz rate at 60 and turn the voltage up.

There is no variable resistor, be nice if there was.

I have a 45 coming, I will stick it in, disconnect the gen from the boat and using my Fluke, see what I get voltage wise, so long as I don't damage anything even if it doesn't work I'm only out $12.


DotDun, I thought I had read where you did that earlier, and that is likely what put me onto changing the Cap uf value, I doubt I though of it myself
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Old 15-09-2016, 12:25   #21
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Re: Capacitor uf Rating

Thanks to you, too, DotDun. And for posting that info.
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Old 15-09-2016, 12:42   #22
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Re: Capacitor uf Rating

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I'm at 62 hz no load, and 60 under 21 or so amps, my normal load, but it does sag to 58 or so under heavy load, approaching the engine limit, no smoke, but you can tell she is about maxed out, you can hear it labor. She will make 30 amps, but just barely and I wouldn't keep it there, now if I do the boats 30 amp breaker will pop, so in truth the gen and boats electrical system are pretty well matched. Of course as voltage drops, amps go up, so 34 amps at 105 voltage is the same power as 30 at 120, so the voltage sag will drive my amps over limit.
What happens though as the RPM drops just a little voltage sags to 105 or so and I know long term that is not good for my electric motors and who knows what all else, they are designed I believe to operate on 120, average residential power is approaching 125.
I will crank up the RPM if I have to, I'd rather if possible leave the hz rate at 60 and turn the voltage up.

There is no variable resistor, be nice if there was.

I have a 45 coming, I will stick it in, disconnect the gen from the boat and using my Fluke, see what I get voltage wise, so long as I don't damage anything even if it doesn't work I'm only out $12.


DotDun, I thought I had read where you did that earlier, and that is likely what put me onto changing the Cap uf value, I doubt I though of it myself
No load, I'm about 63hz, full load is still above 60hz, but just by a tenth or two.

My experience tells me the 45uf will increase your voltage......but, if it blows up, I never said that!!!

The nice thing about capacitor voltage regulation, it's cheap - $20 for 2 capacitors, in my case vs. $900 for Onan/NL AVR board. The downside is voltage regulation is not as tight (10% vs 5%). Hence, I can handle 125v no load to 112v full load, but I don't want it to drop below 110v or so.

A decent digital volt meter will have a capacitance feature, you may want to consider picking one up. I ordered 35uf off Ebay once, got them and they measured 45uf. I threw 'em away, wouldn't even try them.
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Old 15-09-2016, 12:48   #23
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Re: Capacitor uf Rating

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thanks Thomm for the feedback. I'm data throttled again so didn't try to find specific information. Just curious how this setup works as with most things electronic.

Obviously will keep my ill informed opinions to myself. And try to learn something.
I was thinking along the same lines as you were. Maybe we had the same military electronics tech training back in the day......

This Capacitor Regulated Generator Technology is relatively new........the article said 20 years old or so but I didn't notice the date of the article.
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Old 15-09-2016, 14:41   #24
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Re: Capacitor uf Rating

I had a capacitive meter, used it to try to determine if the caps on my airplane magneto were breaking down.
But in downsizing to move on a boat, I have no idea if I still have it, or threw it away. Likely figured I'd never have another use for it and threw it away.
I'm buying a GE Cap off of Amazon, with Prime free two day shipping, for $12. No need for Chinese Ebay electronic parts, although the GE maybe Chinese for all I know.
If this works, I'll blow another $12 and have a spare, my gen head turns 3600, single phase, so I have only one Cap, no electronics that I know of, only other electronic parts is two diodes that I can see. So yes it's probably a dirty waveform although everything works and it's not likely very stable, but it sure seems to be an inexpensive, simple thing. I believe the whole generator is less than $700.


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Old 15-09-2016, 14:53   #25
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Re: Capacitor uf Rating

I don't think a capacitor will change voltage...? It may smooth the spikes. Resistance will. Have you considered just changing your rpm? I don't know your generator... maybe it's something I don't know.
I guess I'm late to the party and uninformed... never mind!
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Old 15-09-2016, 15:22   #26
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Re: Capacitor uf Rating

Okay Cheechako, get in line with the rest of us who came up wrong. Ah well, never to old to learn, just to old to make use of the knowledge, except to maybe pass it on.
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Old 15-09-2016, 16:54   #27
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Capacitor uf Rating

Here is hoping it works. I won't go down to next weekend though, this weekend my Mother in law is gracing us with her presence


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Old 15-09-2016, 17:36   #28
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Re: Capacitor uf Rating

[QUOTE=a64pilot;2214024]Here is hoping it works. I won't go down to next weekend though, this weekend my Mother in law is gracing us with her presence


Wait till these relatives think they would like to visit you in La La land. "Oh could you turn off the ships clock, the noise bothers me".
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Old 24-09-2016, 11:09   #29
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Re: Capacitor uf Rating

OK this is what happened, I went to put in the 45 uf cap and happened to look at the factory cap that the spec called for is 40 uf.
It had a 37.5 uf in it. I speculate that they "tune" the generator at manufacture by using slightly different caps and that this one was not in there as a mistake. Instead of jumping all the way to 45 uf I put in the spare 40 uf that I had. Voltage jumped up by about 10 or so, so now I'm sitting at anchor with a 22 amp load on the generator and it's running right at 115 VAC and right at 60 hz.

So I can confirm that increasing the uf of a capacitor regulated generator, in my case going from a 37.5 to a 40 increased voltage by about 10 VAC. Unloaded I'm running about 130 VAC and about 63 ha.


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Old 24-09-2016, 11:23   #30
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Re: Capacitor uf Rating

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OK this is what happened, I went to put in the 45 uf cap and happened to look at the factory cap that the spec called for is 40 uf.
It had a 37.5 uf in it. I speculate that they "tune" the generator at manufacture by using slightly different caps and that this one was not in there as a mistake. Instead of jumping all the way to 45 uf I put in the spare 40 uf that I had. Voltage jumped up by about 10 or so, so now I'm sitting at anchor with a 22 amp load on the generator and it's running right at 115 VAC and right at 60 hz.

So I can confirm that increasing the uf of a capacitor regulated generator, in my case going from a 37.5 to a 40 increased voltage by about 10 VAC. Unloaded I'm running about 130 VAC and about 63 ha.


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Sounds like you have a solution!
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