Genset voltage reg: capacitor vs. AVR

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On 2/18/2013 12:33 AM, Michael A. Terrell wrote:

We could always ask Nikola. ^_^
TDD
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The Daring Dufas wrote:

Nah, he's always so tesla...
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On 2/18/2013 2:44 AM, Michael A. Terrell wrote:

At least he alternates. ^_^
TDD
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wrote:

Thanks for the link. From that thread, I determined that the keyphrase I needed to google was "alternator feedback capacitor".... That gave me the link to a paper called "Field Initiation Design Fundamentals for Pulsed Alternators" which has an abstract giving a short explanation of how the capacitor works. This was an IEEE paper.
It is simply a bootstrap giving feedback to the field of an alternator....... Not a particularly good regulator, but sufficient for non precise applications. I had never seen this before, as I had only used electronic regulators to the field windings of an alternator with a DC field and not pulsed alternators.... Live and learn.....
Anyway, if the voltage regulation is critical , an electronic regulator would work far better.
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news:11864198-e5a3-4016-b3dc->

Would it be better to regulate the peak, average or RMS voltage if the load draws non-sinusoidal current?
I became concerned with the peak after a poorly regulated generator burned out the transient voltage suppressors in an outlet strip, in a cloud of purple smoke. jsw
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ulator would work far better.

If the output is non-sinusoidal alternating current, it would depend on the use. If equipment is being used that uses the entire waveform, such as a heater, the RMS would be the choice. For a motor, I'm not sure, but I'd go with RMS unless better info is found. If the device is electronic, which uses a peak detector to form a DC for a power supply, the peak would be reasonable.... However, it would be necessary to look at the output waveform to make a really informed choice. For instance, if the output is a square wave the choice would be different from a stepped sinusoid. Note that rotating machinery will put out a sinusoid but many generators today use a speed lower than 3600 rpm and use an inverter to make the frequency controlled output voltage, often a "stepped sinusoid", which has the RMS of the sinusoid AND the peak level of the sinusoid, but synthesized in steps.
Also, if the output is DC or pulsed DC, a capacitor stabilizes the voltage by reducing the ripple, the same function as the battery in an automobile. For this appication a big ass capacitor in parallel with a resistor can, in many cases, take the place of the battery. If a load is always present, the resistor won't be needed. \ Such stabilizing loads are often used in stabilizing the DC system in large RVs if a battery isn't used.
The requirements are different for an AC system. That accounts for some of the different solutions posted here.
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wrote:

I asked because I have several small generators that regulate voltage poorly, typically they have to be set around 140V at no load to maintain 105-110V at full load. Unless I'm running one large insensitive load like the washing machine I pass the power through a metered 20A Variac indoors and change its setting as I add or remove loads.
The APC SmartUps I found at a flea market recently looks like it would handle the variations automatically without modifying the generator. They are too expensive new and not common enough used to be a general solution.
Unfortunately I don't know how much overvoltage things will stand without frying them. My house spiked up to 180VAC once from a powerline problem and the lights buzzed loudly. I knew there was an intermittent fault and was monitoring it. It turned out to be a corroded splice in the neutral in the drop from the street. I needed good evidence to convince the power company to replace the meter box and weatherhead.
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Sorry, Jim, But your wide applications are getting way outside my area of expertise...... I , personally, would use the variac like you are doing, and set each application up as needed. For a general purpose application to do everything for every purpose, tho, I'd probably buy a big generator as used in RVs, or "whole house", and make sure the warranty is paid up..... I doubt that this opinion is of any use to you, but that's the best I can offer.. Good luck...
PS.... As an afterthought, an interested reader might consider your "neutral" problem, and check the tightness of their neutrals in the meter box, as well as the ground wire connection beside the meter box.... It ain't rocket surgery..... The power company doesn't like people going into the meter box to tighten up the terminals... .... to easy to steal power...
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news:6820d266-c2c7-41e0-9bc1-

The power company did try that first. The repairman and I cleaned the meter box contact recesses with my collection of needle files and nachinists scrapers. It seemed OK for a while, possibly because we had pulled on the weatherhead connection, then I started to see the lights flash and buzz at around 4:30PM. The line-to-line voltage held steady, it was the neutral that was bouncing around.
I finally tracked it to a tree trunk shadow passing at that time over the aluminum cable coming down the house, causing a brief drop and then rise in its temperature.
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Wow ! Talk about a weird problem.... well, stuff happens !!! Thanks for the post. I doubt that it would have occurred to most readers and now we have something to think about if it happens to us.... ...... tighten the neutral connectiona the weatherhead....
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On Sun, 17 Feb 2013 16:33:03 -0800 (PST), Robert

A lot of folks replace the battery on English motorcycles with a big cap for the same reasons
Gunner
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So caps ARE regulators of sorts? Not just tuning/balancing?
I wonder, if/when I put on this AVR doodad, if the caps should be removed, or left in place.
--
EA




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,

Do you have the Meccalte spec sheet, manual etc for the actual generator head? That would be my source for information. Assuming of course that the offered voltage regulator from the company you bought the assembly from is using a M voltage regulator on an M generator.... I would think the cap does need to be removed as the electronic voltage regulator is going to control the winding field instead of relying on the cap. generator?
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I downloaded that paper, it's not actually using the capacitor as a regulator at all. This is a trick for starting up a an air-core alternator which doesn't have any residual magnetism to start current in the armature when it's turned on, unlike a conventional steel-core generator. I don't think any of this applies to the discussion at hand. --scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

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On 02/17/2013 06:57 AM, Robert wrote:

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

--
fact check required

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That would be the mechanical engine governor.
An AVR sharpens this up.
Yes

to

See my other post to a discussion.

d

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.
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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.
--
EA


Just some more things to think about.
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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.

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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?

ltho

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

y a

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.

ne of

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.

ve

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.

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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.

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The engine governor has nothing to do with the output voltage regulation, really.
With a conventional AC generator, the speed of the engine governs the output frequency. The generator HAS to run at constant speed, usually 1800 rpm, in order to get 60 Hz out of the generator. Change the engine speed, you change the line frequency.
This is why conventional AC generators ALL have a device to regulate the field coil voltage in order to get constant output voltage. Some of these devices are better than others.
The inverter-style generators are different and what makes them such a big advancement is that they allow you to run the engine at different speeds for different loads by decoupling the engine speed and the final output frequency. --scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

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On Feb 18, 11:12 am, snipped-for-privacy@panix.com (Scott Dorsey) wrote:

BS. And your reference for that claim, which flies in the face of physics, would be?

e

No shit sherlock and you also change the voltage.

ese

That's true and why EA is asking about a cap versus a ture electronic voltage regulator.

I pointed that out several posts ago.
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