Genset voltage reg: capacitor vs. AVR

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What are the pro's/cons of each?
One pro for caps is that they are cheaper! The AVR ditty for my unit would cost another near-$400. The pro for AVR is, presumably, much tighter voltage regulation with load.
But mebbe AVR has its limits ito ruggedness?
The voltage swing on my genset is 250 - 230 V, 0-50 A. Units with AVR claim 1-2% regulation.
Should I spring for the AVR? If a major outtage occurs, I'll be running cnc equpment from it.
--
EA




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I don't understand your question. If you mean "capacitors" when you say "caps", I don't know how they would deal with output voltage regulation in any meaningful way. What kind, model and serial number of genset do you have that currently has no voltage regulation built in to it?
Pete Stanaitis ----------------
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uld

y has

I think he's saying he has a cheap generator that uses a cap for voltage regulation. They apparently do that by using a cap in conjuction with the power source for excitation.
But a better question might be why would someone living in NYC, who has a critical need to run CNC eqpt during a major power outage, be concerned about spending $400 for decent voltage regulation? You think that would have been in the decision for the generator from the start.
And how could anyone forecast what regulation is required, what the possible voltage swings might be, without knowing what all the actual loads are, what their tolerance is, etc?
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wrote:

I think he's saying he has a cheap generator that uses a cap for voltage regulation. They apparently do that by using a cap in conjuction with the power source for excitation. =============================================== Except it's not so cheap. Which is why I was disappointed in the regulation. AVR IS available for the unit, they just chose to use caps..
But a better question might be why would someone living in NYC, who has a critical need to run CNC eqpt during a major power outage, be concerned about spending $400 for decent voltage regulation? You think that would have been in the decision for the generator from the start. ============================================ I thought it did have AVR, and the point was, which you of course missed (in your premature judgmental fervor), was *how much* better can AVR be expected to improve things.... more of a general query as to how these things work.
And how could anyone forecast what regulation is required, what the possible voltage swings might be, without knowing what all the actual loads are, what their tolerance is, etc? ================================================ That's the mfr's job. I in fact DID measure these things, whose values I gave in the OP.
What size is YOUR generator, what fuel is used, and how well regulated is it? And what do you do about the noise? Or do you just let your neighbors suffer?? lol
--
EA




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I'm not sure how that works.
The original AC voltage regulation system, which I think is called a Tillen regulator, and dates back to the 19th century, involves a buzzer that produces a square wave whose duty cycle is inversely proportional to the output voltage of the generator. This is integrated by a capacitor into a voltage that is inversely proportional to the output and that drives the field coil. This is how automotive alternators used to work until the seventies.
(There is another method used with big generators that involves a DC motor generator set used to regulate the field coil, but we are talking small gensets here.)
Anyway, the Tillen regulator is history and as far as I know nobody is using it today. Instead they use a solid state circuit whose output voltage is inversely proportional to the AC input voltage. Early on these used SCRs that acted as switching devices more or less like the Tillen mechanism, but by the 1970s they were mostly using big bipolar transistors. This is what I think the original poster is calling an "AVR" and it's pretty much how regular constant-speed AC generators work today.
Now.... the interesting thing is that today we have a whole new breed of generators which are not constant speed. They generate AC, which is rectified and then used to power an inverter that creates constant frequency AC. This means the engine throttle can be adjusted to regulate voltage as well as the field coil... and it means the engine is throttled way back where it is quiet when there is little load and opened up all the way when there is more load. There's a lot more stuff inside the box to go wrong and some of the inverters are kind of crappy (although I am really amazed at how good a waveform and how little RF noise we get from the Honda 2000i), so repair and diagnosis is a little trickier.
But if I were buying a baby generator (sub 5KVA) today, I would definitely go the inverter route. In the 5-20 KVA range it would depend.

Personally, if I were running CNC equipment, I'd get out of NYC as fast as possible and get to a place with better support for manufacturing and lower tax rates... --scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

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wrote:

Which is what cars do, right?
In generators, I think they call it automatic idle, in the better units.
There's a lot more stuff inside the box

There's also the issue of "true sine" vs. std inverter output. True sine is sig'ly more expensive.

AMEN!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! Hopefullyl they'll let me into VanCouver, BC, Canada.... LOL
fuknBloomberg has no sympathy for people unwilling/unable to spend $1 mil on a 1 BR apt, whose rent (before he and Guiliani gutted rent control) was proly $500/mo.
"Buying" apts. is essentially mega "key money", which is illegal. But when sed key money allows you to "flip" a hot potato to some other sucker, which generates all kinds of minicipal revenue, then I guess it's ok.....
Parts of NYC used to be machining meccas, partic. in the small parts industry (spring-making, lighting, for example), and in knitting. Pre-1990, parts of Brooklyn, Queens were the knitting capital of the world, I'm told, with a large machining infrastructure (mom&pop machining, btw) to make the many *very* intricate parts that would wear in the needle/knitting process.
--
EA


> --scott
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On 2/17/2013 9:09 AM, Scott Dorsey wrote:

I believe you got your timeline a bit off on automotive generators. My 63 Dodge had an "alternator" with a transistorized voltage regulator. My family had a 55 Chrysler which had a "generator" and electromechanical voltage regulator. I do believe the GM cars from the 70's had the solid state voltage regulator built into the alternator itself. ^_^
TDD
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On Feb 17, 10:09 am, snipped-for-privacy@panix.com (Scott Dorsey) wrote:

>> a cap for voltage regulation. They apparently do that by using

> I'm not sure how that works.
You mean whether the cap is shunted to the load and power source? Because "in conjunction" means "in series with" right? At least, that's how I've heard it mentioned before.
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wrote:

would

tly has

Many of the transformers and other circuitry in lower manhattan are still being put back up. Most of that stuff was underwater (salt water) south of 32nd street. I wonder if he's reparing generators. I'd repair the diesel ones. There'd be more money in those, but stick to repair manuals and their one eight hundred tech numbers.
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Ditto. ergo my Q. I guess they must in some fashion, just like you balance rpc's with caps.

http://www.generatorsales.com/order/Honda-16kw-Propane-Generator.asp?page=H04599 modified for tri-fuel.
It is regulated, just not to 1 or 2%, a swing of 230 to 250 V, from 50+ amps down to zero amps. If you at mid-load it's 240 V, that's +/-10V, which is not terrible, but it's not 1% either.
Assume no electrical-type regulation at all. There is something between the generator itself and the gas engine that ups fuel flow with load, maintaining a semi-constant voltage. An AVR sharpens this up.
I don't quite understand how this works, and part of the intent of Q was to shed some light on this.
I also figgered that if the feedback between generator and engine was good enough, AVR wouldn't be needed. So basically I"m curious about the design of these things.
--
EA



> Pete Stanaitis
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I thought that it was a possibly that you had heard of a "capacitor regulator' that I haven't, after 35 years as an electronics design engineer. So I googled the subject and was unable to come up with a single circuit/instance where a capacitive system was used as a regulator....
I have the background to comment on the subject, so if you will provide a website that comments on how a capacitor or "capacitive circuit" can regulate the output of a genset, I will study it and give you an opinion, which, obviously you can accept or reject....
I don't post this to insult you, but I really don't see what you are asking ..
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On Sun, 17 Feb 2013 06:57:39 -0800 (PST), Robert

Without following this thread, it seems to me that he's looking at a filter circuit for suppressing voltage spikes rather than a voltage regulator.
I'll leave it to you to comment.
--
Ed Huntress

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OK.....
I am actually reciting what the company told me. Apropos of your comment (and Pete's confusion, as well), what I think they actually meant was that the caps are used to TUNE or balance the system, somewhat like you would the legs of a 3 ph rotary converter -- which I do all the time.
As I mentioned above, the "first stage" of regulation is accomplished via some linkage between the generator and the motor, as in gas powered welders -- which I've always been curious about how that works. AVR would then seem to improve this.
Not sure how all this occurs, just exploring the idea of tighter regulation.
Part of my Q was a suspicion that an AVR proly regulates voltage more tightly, but perhaps at the expense of raw current flow. Iow, I might get "better" juice, just less of it. Just wondering.....
--
EA




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For lower power demands a high-end APC SmartUPS can regulate the AC output if the line goes high or low. I got one free with bad, swollen batteries. It works without them, or with external batteries plugged into the rear connector. http://www.apcmedia.com/salestools/ASTE-6Z8L9X_R0_EN.pdf
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y would

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It's not hard to find discussion of caps as voltage regulators. Here's an example, about a third of the way down in this thread:
http://www.smokstak.com/forum/showthread.php?t 338
Seems like a pretty crappy thing to find though on a $3000 generator.
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It's not hard to find discussion of caps as voltage regulators. Here's an example, about a third of the way down in this thread:
http://www.smokstak.com/forum/showthread.php?t 338
Seems like a pretty crappy thing to find though on a $3000 generator. ================================================= Inneresting thread. But I think one can conclude that caps are not regulating, they are tuning, balancing. with mebbe an itty bitty bit of regulation as a perk to tuning.
But if you follow the op Jim McIntyre, what his cap(s) did was raise/lower the voltage. The unit itself, apparently pretty high quality, seems to have had inherently good regulation between the generator itself and the motor. Anthony W. commented that
"It sounds as if Kubota did their homework on the winding ratios in your set. As you found, the cap value isn't too critical in a "good" set within a reasonable range. Problems usually only show up when a certain critical cap value is exceeded. Also in the case of a non-linear load such as a switching power supply,(if you run your computer off of one) plug an incandesent lamp or two in as well. I don't know that it would hurt anything, but the waveform looks "slanted" on a 'scope when only a switching-type load is applied. The only troubles I have had with the several old Cap regulated sets I have owned are bearing issues and the cap going "open". "
And the quality of the linkage between the generator/engine was proly superior.
Notice, tho, that when McIntyre increased his cap size, the voltage regulation went from about 1% to 2%. Note that in mine, a much larger unit, the regulation, from midpoint, is 4% right now -- not terrible terrible, but again, not 1%.
--
EA








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On 2/17/2013 9:43 AM, Existential Angst wrote:

I don't think it would be too far out in space to think of the capacitor regulated generator as being related to a ferroresonant transformer or a CVT, Constant Voltage Transformer. The only difference is there is a mechanically rotating winding. ^_^
TDD
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The Daring Dufas wrote:

A CVT requres a sepereate winding to resonate with the cap. If it were part of an active circuit, the Q would be too low to do any good.
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On 2/17/2013 12:04 PM, Michael A. Terrell wrote:

I did write "related". ^_^
TDD
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The Daring Dufas wrote:

Maybe a third cousin, twice removed? :)
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