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Kohler - unsteady voltage


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  #21  
Old 12-23-2018, 07:32:38 PM
Zephyr7 Zephyr7 is offline
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Default Re: Kohler - unsteady voltage

Run one more load test for me. Try to get the load up as high as you can WITHOUT running your TV or other fancy electronic loads (computer, etc). Use lights, ideally incandescent, heater, oven, stuff like that — resistive loads.

If the voltage gets wonky with heavier and heavier loads like these, you have a normal type of voltage regulator problem. If the load is ok, then...

If the load gets wonky with the TV connected, and only when the TV is connected regardless of the other loads on the set, then you have some kind of power factor related voltage regulation problem. This might be with the genset, but it might also be due to certain unusual failures of the TV power supply.

Some types of DC power supplies don’t draw power cleanly over the AC sinewave, they draw power in large spikes usually at the voltage peak of the sinewave. Sometimes this causes problems. The effect is to draw way larger amperage for a brief period to get the amount of power (watts) the device needs. Wattage is volts * amps, but in AC, it’s really the area under the sinewave during which the load is drawing power, so volts * amps * time (simplified a bit). I’ve seen very short and VERY high current load spikes cause problems before even on utility systems. It’s very easy to see when using an oscilloscope, especially with a current probe.

If your TV is getting old, it may be the power supply has a problem. The utility supply is essentially so massive compared to your genset that you wouldn’t see the issue there. When connected to your genset, which is a “soft source” (it dips much more under much smaller loads than the utility voltage would), you see it.

Bill
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  #22  
Old 12-24-2018, 12:14:15 PM
Trekrider2001 Trekrider2001 is offline
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Default Re: Kohler - unsteady voltage

The test you described is what I did. I added the load in steps, 1)Space heater, 2) oven, 3) lights, 4) TV with its Bose sound system. Only when I got to 4) did I see the unstable voltage (down to 90v). I have to say, however, that I have had the generator for years and this TV for about half the time. The Bose for more time than the generator. I have never seen this level of voltage instability during any past power failures. Also to note, during the brief (~fraction of second) dip to 90 V, I could hear the generator briefly labor. When I add the space heater, there is no such laboring. I can't imagine that the TV/Bose combination can load the generator more than the space heater. I do now have a large number of LED lights in the house. Could be adding to the problem? Don't each have a small transformer in the base? (ie they are 120 volt LED that replaces 75W halogens in the kitchen). Can you get a resonate wave going between the generator and all these transformers?
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  #23  
Old 12-24-2018, 12:56:12 PM
Birken Vogt Birken Vogt is offline
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Default Re: Kohler - unsteady voltage

I don't know where to go with this problem. Sometimes you just have to be there.

What I can say for sure is that if the engine is laboring, even for a second, all that power is going somewhere and being dissipated. It can go into its own windings, or a short down the line, or some faulty device. If you hear the engine lug, very shortly smoke will be coming out of the offending part.

Sometimes that can be beneficial in troubleshooting. Sometimes it can be very expensive.

It could also be that the engine was having trouble such as lack of fuel/spark plug that just sounded like loading but wasn't really.

Funny story, I was load banking a long-disused unit at 100% and hours into the test it lugged and smoke came out. Then it picked up and continued. No problem noted on meters or anything. Finished load bank with no further issues. I figure it was a wasp nest or something being blown out the exhaust.
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  #24  
Old 12-24-2018, 11:11:56 PM
Zephyr7 Zephyr7 is offline
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Default Re: Kohler - unsteady voltage

Sounds to me like a problem in either the TV or Bose system power supply. I’d suspect the TV since the plasma TVs have beefy power supplies. Something probably died in that power supply, possible in the first stage power factor correction circuitry which I bet it has.

Yes, it’s possible that your TV is causing this. I saw once, years ago at work, a problem that came up periodically and overloaded a mid size (16KVA) UPS system. The issue was occasional and cyclic (read that as a very slow cycle). If the UPS happened to be on battery at the time of the issue, the UPS got toasted and would need repair. The issue was a very brief overload caused by a switching power supply in one of the supplied computers (one of close to 100 of them). I was never able to find the faulty power supply, but I saw the UPS get toasted twice, and I saw the momentary overloads get logged lots of times.

I suspect the issue was a very brief, but very large, overload. You’d need an oscilloscope to see it. I actually caused an issue like this once with a thyristor circuit I used to ramp up a large transformer. I was triggering the triac with a pulse, and the large inductive load caused a phase issue with the current waveform such that I was triggering the triac on on alternating half cycles and not every half cycle like I’d thought. The brief current draws were hundreds of amps, and did not trip a 15 amp breaker since they were so short. I DID see this when I tested with an oscilloscope, but I was setup doing circuit design so I had a nice controlled lab to test with.

Anyway, the only thing I can think of that might filter this out is a constant voltage transformer (a ferroresonant transformer) used as a line filter for your TV. Best is to either service or replace your TV since the failure might get worse. Note that you really need to check with an oscilloscope and a current probe to be sure what’s going on, but what you’re describing really sounds like a partially failed switching power supply to me.

Can you borrow a small genset to run only your TV? If the small genset does the same thing, then you know it’s your TV at fault. Don’t use an inverter generator for this test.

Bill
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  #25  
Old 12-24-2018, 11:52:05 PM
Mark Dieckmann Mark Dieckmann is offline
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Default Re: Kohler - unsteady voltage

Quote:
Originally Posted by Trekrider2001 View Post
The test you described is what I did. I added the load in steps, 1)Space heater, 2) oven, 3) lights
It seems to me that you need more load for testing purposes. Do you have an amp meter? A clamp type meter can help determine the load on the generator and possibly see the spikes. The heater and oven are only about 5kw. Try adding more resistance loads. A water heater, when heating of course, is approximately 5kw. Surface burners on the stove vary but might average 1kw each. I am curious how it would preform at 80-100% load.
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  #26  
Old 12-26-2018, 02:20:22 PM
Trekrider2001 Trekrider2001 is offline
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Default Re: Kohler - unsteady voltage

Not sure what additional load will show. The load I gave it plus the TV generated the problem (dimming lights, voltage fluctuation).

Question: without load I measured 119-120. But the digital voltmeter, never showed a steady voltage. As the load increased the voltage dropped. How steady is the voltage supposed to be? The street voltage is rock solid steady, while the generator voltage never settles down. My theory now is that the voltage regulation (or connector losses maybe due to corrosion, or loosening) interacts with the TV power supply and they are both trying to correct things and then get balled up. If I can get the generator to be stable, then it might not trigger the TV power supply? What do you think?
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Old 12-26-2018, 03:18:35 PM
Zephyr7 Zephyr7 is offline
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Default Re: Kohler - unsteady voltage

Really bad power factor loads can cause issues with voltage regulation. The generator will never be as stable as the utility because your load is large relative to the generator capacity. Your load is always very small relative to the utility system capacity.

Is your digital meter a “true RMS” meter? Non-true RMS meters will be fooled by oddball voltage waveforms (which can be seen on bad power factor loads sometimes), so you might be seeing issues that aren’t really there due to an inherent limitation of your test equipment.

Bill
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  #28  
Old 12-26-2018, 04:03:48 PM
Trekrider2001 Trekrider2001 is offline
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Default Re: Kohler - unsteady voltage

Its a Beckman Tech 310 - the manual says True RMS.
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Old 12-26-2018, 09:52:24 PM
Mark Dieckmann Mark Dieckmann is offline
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Default Re: Kohler - unsteady voltage

I was simply trying to determine if the generator would produce good voltage under load without the TV. If so then you have most likely found the problem. You stated the problem only developed with the TV on. I was only trying to offer ideas to try to help you as is everyone here... Clamp type amp meter?? It's a good basic tool to determine the load on the generator.
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Old 12-26-2018, 10:52:12 PM
Trekrider2001 Trekrider2001 is offline
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Default Re: Kohler - unsteady voltage

Many thanks to all the comments and ideas. I re-did the load test after I changed the surge protector feeding the TV and sound system. Without the TV on, all seemed fine. Then I turned on the TV and all seemed fine, for about a minute and then the lights started to dim (in a cycle, normal, then dim, then normal), then dim more and more until they pretty much went dark, and the TV lost power and went dark. The dimming was clearly in a cycle. All this time only the oven was giving load. I then turned off the TV and all seemed fine for about a minute and then the lights dimmed cyclically again, but not as dark. but in a cycle that was annoying. I also measure the power consumption of the TV (using a Kill-A-WATT) and it ran between 125 -510 watts. The lighter the scene on the TV the more power. Also I measure VA and Watts. The VA was always higher by maybe 25%. Hard to tell as the power fluctuates with what is playing and I have to toggle between these settings. So the problem exists (not as bad) with the TV off; there does not need an excessive load to create the problem; during the drop outs I could hear any difference in the generator noise (ie it did not labor or change pitch). So it looks like the generator is trying to follow the load but can't fast enough and falls into a cycle (positive feedback loop) that makes the voltage fluctuations grow. Is this a gain adjustment on the ADC 2100? Why would I have to change it? It all worked before. ADC 2100 fried? Its about $1000 to change out!
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