Genset voltage reg: capacitor vs. AVR

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.

Reply to
Existential Angst
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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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Reply to
Pete S

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?

Reply to
trader4

Ditto. ergo my Q. I guess they must in some fashion, just like you balance rpc's with caps.

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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.

Reply to
Existential Angst

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 ..

Reply to
Robert

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

Reply to
Existential Angst

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.

Reply to
Ed Huntress

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

Reply to
Scott Dorsey

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.....

Reply to
Existential Angst

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.

Reply to
Existential Angst

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:

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Seems like a pretty crappy thing to find though on a $3000 generator.

Reply to
trader4

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.

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Reply to
Jim Wilkins

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:

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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%.

Reply to
Existential Angst

That would be the mechanical engine governor.

An AVR sharpens this up.

Yes

See my other post to a discussion.

Do you realize what you got for $2800? They take a Honda engine and bolt it on to some generator made by someone else. Perhaps you can shed light on to who that someone else is, but given that it uses a cap for voltage regulation, I would not be surprised that it's a cheap Chinese one. Then they take pretty pictures of the thing with Honda showing all over in the pretty pics and a lot of people make the assumption that they are buying a Honda generator. I don't believe that is the case.

Further arousing suspicion is that they claim it's 15KW. Then if you read the specs, it says it's rated at 13.5KW continuous. Then they say it has a 50 amp main breaker, which equates to 12KW, in my world.

You with me so far? Further arrousing suspicion, they quote fuel consumption in gallons, ie it's based on running the engine on gas. So, next, let's look at the spec for a Honda GX690. It says it produces 22hp running gasoline. I'm no expert in conversions from gasoline to nat gas, but AFAIK, when you run a gasoline engine on nat gas, you have about 15% less energy output. Maybe someone has the exact number. That means you really have about an

18hp engine.

I've looked into generators a bit and what it takes to power them. I don't think you can get 15KW out of an

18hp engine. A Generac 12KW unit for example, uses a 26hp engine.

Just some more things to think about.

Reply to
trader4

it's possible they're being used for power factor correction rather than regulation. pfc gets to be important with some reactive loads.

Reply to
jim beam

That would be the mechanical engine governor. ====================================================

I sure would like to know the details on how those work.

An AVR sharpens this up.

Yes

See my other post to a discussion.

Do you realize what you got for $2800? They take a Honda engine and bolt it on to some generator made by someone else. Perhaps you can shed light on to who that someone else is, but given that it uses a cap for voltage regulation, I would not be surprised that it's a cheap Chinese one. Then they take pretty pictures of the thing with Honda showing all over in the pretty pics and a lot of people make the assumption that they are buying a Honda generator. I don't believe that is the case. =====================================================

McCaulte (sp?) makes the generator.

And yes, they mix'n'match.... but presumably they do it pretty well, altho I got a li'l short-shrifted on the AVR deal.... I don't know that they are being misleading, as much as emphasizing the Honda part.... LOL Thin line, admittedly.

Further arousing suspicion is that they claim it's 15KW. Then if you read the specs, it says it's rated at 13.5KW continuous. =============================================

This is typical. Generac does this.

Then they say it has a 50 amp main breaker, which equates to 12KW, in my world. ======================================

Yeah, I noticed that. And they trip fast, too! I may put in my own 50 A slower-tripping or even 60 A breakers.

You with me so far? Further arrousing suspicion, they quote fuel consumption in gallons, ie it's based on running the engine on gas. So, next, let's look at the spec for a Honda GX690. It says it produces 22hp running gasoline. I'm no expert in conversions from gasoline to nat gas, but AFAIK, when you run a gasoline engine on nat gas, you have about 15% less energy output. Maybe someone has the exact number. That means you really have about an

18hp engine. ===============================================

Again, par for the course. I simply went for the most watts. Those watts will be similarly de-rated in most scenarios, so I just went with the biggest number.

I've looked into generators a bit and what it takes to power them. I don't think you can get 15KW out of an

18hp engine. A Generac 12KW unit for example, uses a 26hp engine. ================================================

Oh, but I did get very nearly the full 13.5 continuous (on gasoline), and proly could have gotten sig. more. I'll have to jump/replace the breaker, tho. Already at near-full load, it started a 26 gal compressor, w/ nary a hiccup.

A 26 hp engine for 12 kW is suspect as well, from two povs: First, I suspect Generac hp is like Sears hp. Second, if it IS 26 hp, yer just sipping lots more gas.... which was one of the things I was going to discuss in my upcoming Generator Manifesto..... big-azz generators, in no-load conditions, are not economical.

I really couldn't find much better overall bang fer the buck, watt-wise. The Honda motor is a plus, and the unit is VERY compact. Generacs are big and complicated. OK, I spose, for the home-moaner who justs likes to dial the telephone when sumpn goes wrong, and from what I've read about generac, they will be using their telephone fairly often.

Here's some of my take on this:

I would recommend the Sam's club 8,750 W blackmax, at $999, for most people with more than the basic needs. You can get it modified for tri-fuel, and the link I provided sells a modified blackmax for $1600 -- about a $200-$400 preimum over what you would pay if you did it yourself, but with a lot less headache, and somewhat of a guarantee. The blackmax also has AVR, iirc, and performed quite well, before it grew feet.

My unit does not come with a gas tank, but which is actually an advantage, imo, because you just drop the genset's hose down any gas can (or your car's gas tank, if you can snake it in), and Wala, gasoline power.

I went for the 15 kW unit, in the second go-around, for many of the reasons you stated: By the time you get done de-rating for whatever whatever reasons, you have a lot less than when you started, so I figgered I'd just double the size from the gitgo.

Really a lot of g-d work. The other bottom line to all this is that unless you have a water-cooled 4 cylinder unit, you gotta simply build a separate sound-proofed shed for these noise buckets. A lot of my work so far went in to testing, given my cnc liabilities. So far so good, but really a pita -- for sumpn I may NEVER use.

Reply to
Existential Angst

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Find the parts diagram for the Honda engine. They typically rely on centrifugal force. If the engine starts to slow down, the drop in centrifugal force causes movement of linkage connected to the carb throttle.

========================= ====

Meccalte. They are an Italian company. You can buy one of their 12-15KW generator heads for about $800. Not sure what kind of voltage regulation you get for that price. Find the model, look up the spec sheet. I'll bet it says you need 25hp or so to get full power out of it. And I doubt an engine rated at 22hp on gasoline is capable of that running on natural gas. Have you tried running it at full load on natural gas?

There isn't much to it. The engines and generators have common mounting standards that just bolt together.

It's not Generac specific. Take a look at what Meccalte or other generator head manufacturers spec for power required to support

12KW, 15KW, etc.

You can't have it both ways. Well,, actually you can, if you're willing to pay for it. You can buy an inverter based generator. That completely decouples the rotational speed from the frequency. That way, the engine can run at low RPMs with low loads. It makes them very fuel efficient at lower loads and also quiet. But you'll pay $4,000 for maybe 3000 watts.

With a 5 to 7KW generator you can easily run a big house. Except for central AC and electric hot water. On a cheapo

5KW generator we ran 4 refigerator/freezers, two gas furnaces, 2 gas power vented water heaters, plus some lights. That was for two large houses.

But if you need to run a machine shop, then it's a whole different ball game.

You can get a Briggs and Stratton for the same price. It's probably made in China, but at least B&S knows about engines, knows about QC, has a long track record and you know where to find them. Who is Blackmax? Probably a sticker and label on a China generic.

Reply to
trader4

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

Reply to
The Daring Dufas

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

Reply to
The Daring Dufas

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.

Reply to
Michael A. Terrell

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