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Over voltage

Charging System, Wiring, Lighting
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Snakeoil
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Post by Snakeoil » Wed Nov 16, 2011 11:08 am

Thanks for having the patience to explain this to me, guys. I guess I assumed that only the current would rise with load and the voltage would remain constant.

I'm aware of the additional torque required to drive a heavier load. On a turbine-generator set the MW output is controlled by the fuel flow. You crank up the throttle to make more MWs. If the load increases and the governor does not respond speed/frequency drop. But I was not aware that voltage dropped, too. Maybe the generator controls maintain voltage by cranking up excitation. But I thought that was just for VARS.

I have to absorb all this. Can't process the data like I used to. I need to see how the various laws confirm this. It will give me a much better understand and help me troubleshoot in the future.

Thanks and regards,
Rob

Wilf
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Post by Wilf » Wed Nov 16, 2011 11:43 am

Rob,

In an automotive alternator when the load increases and the voltage drops, the regulator adds more excitation current to the Field windings to bring the voltage back up to the design charging voltage.

What's the VAR thing that you have refered to?

Wilf

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Snakeoil
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Post by Snakeoil » Wed Nov 16, 2011 2:37 pm

VARS are reactive power. VARS stand for volt-amps reactive.

The big motors and similar devices in large industries as well as the cumulative small motors running on the grid require reactive power. But they also produce reactive power if I remember correctly, so the power gen plants have to produce some amount of reactive power. It's also called Power Factor. As I understand it, it does not cost fuel, but does cost generator capacity so you cannot produce as many MWs if you have to produce some MVars. So, there is a charge for it. But an industrical plant can offset the cost by installing large capacitors where the power comes into the plant. Somehow they offset the need for VARS and save themselves money.

After sending my last post, I remembered that our generators have a system referred to as the AVR or Auto Voltage Regulation. I suspect that it monitors the voltage on the grid and the unit and matches the unit to the grid by modulating the excitation, much like you described a car alternator doing the same.

I need to sit down with one of our generator guys and have him give me the generator 101 talk. When they taught us about big generators in Field Engineering school, the instructor was the most boring speaker I've had the displeasure to experience. He would open his mouth and I would fall asleep. He's the primary reason I know so little about generation basics. Fortunately, we have engineers that work on generators and engineers that work on turbines. The generator guys think turbines are magical.

regards,
Rob

highskyflyn
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Location: Key West,FL

Post by highskyflyn » Fri Nov 18, 2011 7:31 am

Wilf wrote:highskyflyn,

I'm glad to hear you've eliminated a major part of the puzzle, your meter! As Rob says, we've all been there, and I've been there more than once when smoke and/or explosive noises accompanied my "Aha" moments.

You said earlier that you had replaced the rectifier with a new one from Oregon cycles. I googled that name and came up blank. Can you provide a bit more detail on that, as I'm wondering still if the rectifier isn't involved in the problem.

......

Rob,

Ah, the Simpson days! I still have 3 of those beautiful instruments and a swack of salvaged meters on my shelf--love them!

Wilf
I bought the rectifier from a company that's n eBay. Here's a link to there website. www.oregonmotorcycleparts.com/rectifiers.html

Highskyflyn

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davomoto
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Post by davomoto » Fri Nov 18, 2011 9:59 am

Since we're back on the subject of your bike.....It sounds like the starter motor may need some attention. I had a similar issue with my boat many years ago. It would cranks very slowly. I replaced the battery, and it got a little better. I then replaced the battery cables, 18ft long each, with 00 welding cable, and again it got better for a while. I finally replaced the starter motor, and it turned over like a blender on puree'.

Davo
davomoto
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Snakeoil
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Post by Snakeoil » Fri Nov 18, 2011 10:40 am

Yeah, my bad for taking this thread off on a tangent. But I think it was a fruitful discussion.

Looking forward to hear what HSF finds out is causing his problem.

regards,
Rob

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davomoto
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Post by davomoto » Fri Nov 18, 2011 10:48 am

No, very interesting and informative!

Davo

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