Generators and Motors
[Home] - [HELP] - [Forums] - [Library] - [Photo Gallery] - [Groups] - [Classified Ads] - [Subscribe] - [Links] - [Books] - [Sponsors] -

Go Back   SmokStak > SmokStak® Vintage Electrical Equipment > Generators & Electric Motors General Discussion > Kohler Generators
Forgot Password? Join Us!

Notices

Kohler Generators Restoring, maintaining and operating vintage Kohler generators.

Kohler Generators

Kohler 10ROY, AVR G-278598 Failure - Universal AVR Replacement?


this thread has 16 replies and has been viewed 555 times

Reply
 
Thread Tools Display Modes
  #1  
Old 02-14-2019, 01:47:21 PM
TC25D TC25D is offline
Registered
 
Join Date: Dec 2013
Location: Saukville, Wisconsin
Posts: 10
Thanks: 0
Thanked 1 Time in 1 Post
Question Kohler 10ROY, AVR G-278598 Failure - Universal AVR Replacement?

Hello SmokStak friends!

So my Kohler 10ROY is only producing about 60VAC on each leg. This is what it was doing when I bought it many years ago. I replaced the AVR and it ran perfectly (mainly exercising and about 10 power outages) for 7 years (it only has about 300 hours).

This time I went to buy the AVR and POW! It is now $550 and getting tougher to find in new storage vs. old units sitting on shelves.

So I have studied all the schematics to possibly use a Universal AVR.

Here are the challenges:

1) perhaps the biggest challenge is that the excitation field (rotor) on the generator (according to the manual) has an ohmic value of 3.5-4.3 ohms. It seems that all of the Universal AVRs have a min. resistance for the output of 15 Ohms

2) it is clear that the stator has an auxiliary winding to provide separate power from the generator to the AVR - independent of the main stator output (that is often used for power the AVR). this winding appears to be a single winding. Just wondering what it will put out in the way of voltage - I guess 110V?

So, I am looking for an AVR that will replace the Kohler part that is getting really expensive. If it was not for the low rotor ohmic value, the simple universal AVRs on Amazon could likely do the job. Just connect the field winding to the AVR+/- and connect, the sensing to the L1 and Nuetral, the power input for the AVR to the auxiliary winding on the stator (which I assume wants a jumper setting of 110V) and neutral and that should be it.

However, with the AVRs I see having a field resistance spec. of no less than 15 ohms it seems I cant use a Universal AVR that are really inexpensive...literally like $17.

Is there anyone out there smarter than me that can offer up any suggestions?

Thanking you in advance....from Wisconsin. Regards, Cliff
Reply With Quote
Sponsored Links
  #2  
Old 02-14-2019, 02:02:22 PM
Birken Vogt Birken Vogt is offline
Email NOT Working
 
Join Date: Sep 2009
Location: Penn Valley, California, USA
Posts: 2,407
Thanks: 2
Thanked 827 Times in 577 Posts
Default Re: Kohler 10ROY, AVR G-278598 Failure - Universal AVR Replacement?

Flight Systems just came up with a replacement regulator for these, I believe.

The product might still be a little immature, but call them and I am sure they would like to have real users of the product, and it sounds like you know what you are doing, and could help them with real world application.

I have used a universal AVR for medium duration testing on one of these, powered by just the main power windings and ignoring the aux winding.

The real hangup with the universal AVR is the max current it can produce, not so much the field resistance. They just specify that so that the average user can easily measure it and decide if they can use it or not. The field current on one of these is usually OK for a universal AVR, though it might be a bit on the high end of the range.
Reply With Quote
  #3  
Old 02-14-2019, 03:16:25 PM
TC25D TC25D is offline
Registered
 
Join Date: Dec 2013
Location: Saukville, Wisconsin
Posts: 10
Thanks: 0
Thanked 1 Time in 1 Post
Default Re: Kohler 10ROY, AVR G-278598 Failure - Universal AVR Replacement?

Birken - Thank you for the reply. Yes, I have a call into Flight Systems and the one gent I spoke to took my name and number. The engineer he recommend is out sick today..stuff going around.

Also, I have thought about just using the main winding as well for the sensing. I am confident that would work well enough for my residential useage. So you are right on with that input.

The reason I am so concerned about connecting the Universal AVR to the stator field winding is that the manual for it explicitly states a minimum of 15 ohms. Assuming 45VDC out of the AVR, 3.5 ohms as the field resistance would be 12.8 amps. The AVRs I have found (the universal ones) only put out 3 amps. So yes, you are exactly correct...the problem will be the amps. The reality is the fuse in the universal AVRs are typically the 5x20mm units rated 4 amps/250V and fast blow.

The Kohler G-278598 (now updated to F-228605) otherwise known as the Kohler PowerBoost IIIE Voltage Regulator is protected by a 10A fuse (off board and located by the breaker). The orange wire exiting the gel coated circuit board makes its way up to that fuse and back. That is the power for the AVR coming off the auxiliary stator winding.

So, I am thinking that there must be a Universal AVR capable of handling feeding that 3.5 ohm rotor field.

I guess I struggle to come up with $550 for the AVR that I already know will fail with no way for me to repair it. I am a family man with one kid remaining in college...yes, it is money issue.

BTW, I believe what happens is when it exercises itself it sometimes disconnects the breaker when the generator is under load...that is what an ATS does. Believe it or not the Thompson ATS actually synchronizes to the grid supply...both phases. Not quite a bumpless transfer but very close as the lights barely flicker if at all upon transferring from the generator to the main grid power.

So what I can do is switch to periodic manual exercising where I unload the generator before transferring back to the main power grid power. But you and I both know that the generator should be able to handle that ATS (and frankly it did for about 7 years of exercising every 3-4 weeks for one hour).

You know what I really want...I want to use a modernly manufactured, low cost throw away AVR that when it fails I just pull another unit out of my workshop and replace it. These Chinese AVRs are literally $17. I could stock 5 units with no sweat. Alternatively, if I can get a descent priced AVR for say $200 and is repairable I would be ok with that. What I can't stand is a $550 dollar device that is basically a fuse when it fails because I cant get at the components to fix it. If I get pushed too far I will be tempted to build an additional circuit on the output of the Universal AVR to enable the usage of the low cost Chinese unit...in essence a circuit that just changes the excitation output capability but reuses all of the AVR internals.

I love Kohler - they are like 30 minutes from me. Love their products too! However, $550 for this device is no longer prudent for me.

Open to any other ideas folks might have. I find it hard to believe that people living in the country on farms and such with this generator are paying that price for the Kohler AVR...big businesses? yes, small ones and residential folks like me, I doubt it. Someone has cracked this for sure. Just looking for a little advice from someone who has already cracked the case here.
Reply With Quote
  #4  
Old 02-14-2019, 03:45:59 PM
Birken Vogt Birken Vogt is offline
Email NOT Working
 
Join Date: Sep 2009
Location: Penn Valley, California, USA
Posts: 2,407
Thanks: 2
Thanked 827 Times in 577 Posts
Default Re: Kohler 10ROY, AVR G-278598 Failure - Universal AVR Replacement?

It doens't take 45V to excite one of these. Maybe 20-25V. That is why the Chinese one works. Have not tested them extensively. Always paid the money for the real thing when it came time to button it up.
Reply With Quote
  #5  
Old 02-14-2019, 04:12:55 PM
TC25D TC25D is offline
Registered
 
Join Date: Dec 2013
Location: Saukville, Wisconsin
Posts: 10
Thanks: 0
Thanked 1 Time in 1 Post
Default Re: Kohler 10ROY, AVR G-278598 Failure - Universal AVR Replacement?

I have found out that Flight Systems has completed the replacement unit. It is about $400. They also mentioned it is repairable...assuming by them.

What I will do is finish up all system checks confirming the AVR is the culprit. Then will probably order the Kohler Genuine Part. You are correct in your thinking. I am sitting on a 1000lb min., diesel genset that is basically a private powerplant for my complex out here in the country. There is a guy on the net that literally has 30,000 hours on the same unit I have. I keep the fuel fresh in the day tank, the oil and filters fresh even when it barely needs it, the radiator fluid correct and flushed, the battery charged and replaced...I do all the maintenance. In essence it is a $5000 plus setup and I need to look at it that way. What is $500 in the grand scheme of things? I just don't like being in a position where I could potentially connect a new $500 device and poof...it could happen. On second thought I am thinking of going with the Flight Systems solution...2 year warranty, repairable, a little less than Kohler and they seem to have good customer service. I have to make a decision in the next week or so.
Reply With Quote
  #6  
Old 02-14-2019, 05:31:00 PM
Birken Vogt Birken Vogt is offline
Email NOT Working
 
Join Date: Sep 2009
Location: Penn Valley, California, USA
Posts: 2,407
Thanks: 2
Thanked 827 Times in 577 Posts
Default Re: Kohler 10ROY, AVR G-278598 Failure - Universal AVR Replacement?

Just before Kohler made the big price jump a few years ago. We had at least two of those AVRs go "POW" when initially powered up. Undetermined why but both generators were fine, both were replaced with another unit and continue to run to this day. So they might have had a bad run of them for a little while. So I might tend to lean toward the Flight Systems one if I were you. Or put a $17 Chinese unit on and keep 5 spares. It's your money and I don't know what the answer is.
Reply With Quote
  #7  
Old 02-14-2019, 08:16:11 PM
TC25D TC25D is offline
Registered
 
Join Date: Dec 2013
Location: Saukville, Wisconsin
Posts: 10
Thanks: 0
Thanked 1 Time in 1 Post
Default Re: Kohler 10ROY, AVR G-278598 Failure - Universal AVR Replacement?

Berkin, I just did exactly that. I can’t afford to put in a $500 unit and have it blow like a fuse...then what? What would I do- who would I call? I love Kohler but I just can’t take that risk.

I called Flight Systems. They were unbelievably helpful! New universal unit will arrive soon. I will provide an update then. Thanks for the input. I had to go with a current production, non-obsolete solution.
Reply With Quote
  #8  
Old 02-15-2019, 01:43:32 PM
Zephyr7 Zephyr7 is offline
Registered-III
 
Join Date: Mar 2017
Location: Davisburg, Michigan
Posts: 1,979
Thanks: 605
Thanked 1,116 Times in 761 Posts
Default Re: Kohler 10ROY, AVR G-278598 Failure - Universal AVR Replacement?

You can use a beefy ďmetal cladĒ resistor in series with the stator to bring it up to the minimum resistance value needed to make the regulator happy. I like to use two resistors, each half of the total resistance needed, with one in each stator lead.

If you have an auxiallary winding to power the regulator, just measure the voltage with a meter.

I see all these people with old gensets and no replacement regulators and keep thinking I should do some development work and make a schematic/board available for people. I just havenít had the time to do it (or an old regulator to reverse engineer).

Bill
Reply With Quote
  #9  
Old 02-15-2019, 02:05:06 PM
Birken Vogt Birken Vogt is offline
Email NOT Working
 
Join Date: Sep 2009
Location: Penn Valley, California, USA
Posts: 2,407
Thanks: 2
Thanked 827 Times in 577 Posts
Default Re: Kohler 10ROY, AVR G-278598 Failure - Universal AVR Replacement?

Quote:
Originally Posted by Zephyr7 View Post
You can use a beefy ďmetal cladĒ resistor in series with the stator to bring it up to the minimum resistance value needed to make the regulator happy. I like to use two resistors, each half of the total resistance needed, with one in each stator lead.
I think that might actually be counterproductive. The current through the rotor is a constant requirement to maintain generator output at a certain power level.

Adding resistors makes the voltage the regulator is being asked to supply go higher but the current remains the same. Therefore the regulator (and aux winding) is now having to supply a lot more power to do the same thing.

I know this goes against the grain of the thinking on here but I think as long as the max current rating of a particular AVR is not exceeded, it is best to connect it directly regardless of how low the ohm reading of the field is.

If somebody has an alternate explanation let me know.
Reply With Quote
The Following User Says Thank You to Birken Vogt For This Post:
  #10  
Old 02-15-2019, 02:28:24 PM
Vanman Vanman is offline
Subscriber
 
Join Date: Aug 2011
Location: Mission Viejo, California
Posts: 5,397
Thanks: 8,167
Thanked 2,401 Times in 1,634 Posts
Default Re: Kohler 10ROY, AVR G-278598 Failure - Universal AVR Replacement?

/\ This has always been my opinion as well. Why any AVR has a minimum field resistance is baffling...

Edit. Thinking retrospectively, the lower ohm limit may have to do with ensuring a maximum Q value is not exceeded. The field is an inductor, and, all things being equal, the lower the resistance, the higher the Q. I can see a scenario where too high of a Q results in oscillation. Essentially the regulator cannot "turn down" the exciting current quickly enough when needed. Such as a large drop in load.

So, ultimately, the extra resistance may improve the voltage regulation overall, and specifically improve the transient response.

How's that coming from a guy who'll have nothing to do with unecessary electronics (such as AVRs) lol!
Reply With Quote
  #11  
Old 02-15-2019, 03:27:41 PM
Zephyr7 Zephyr7 is offline
Registered-III
 
Join Date: Mar 2017
Location: Davisburg, Michigan
Posts: 1,979
Thanks: 605
Thanked 1,116 Times in 761 Posts
Default Re: Kohler 10ROY, AVR G-278598 Failure - Universal AVR Replacement?

Ding ding ding! Vanman got it

If the overall voltage in the system is lower, chances for oscillation or poor regulation basically increase because it takes a smaller voltage change to affect things. Itís true itís the current (amps) that matters in the coil, but itís the voltage applied that drives that current.

Some of the regulators also ramp down their maximum current ability at the lower voltages. Iím not sure why that is, but thatís what the datasheets say. If the regultors use a FET as the final output device driving the field, the FET basically acts as a variable resistor + a fixed resistance inherent to the device. This could potentially limit max current swings at low voltages if the FETs internal resistance was high enough. Thatís the only thing I can think of anyway. Iíve never really tried to reverse engineer one of the regulator circuits to find out for sure.

If the extra resistance brings the field into the regulators ďsweet spotĒ then itís probably worth using the resistor.

Bill
Reply With Quote
  #12  
Old 02-15-2019, 04:03:54 PM
Birken Vogt Birken Vogt is offline
Email NOT Working
 
Join Date: Sep 2009
Location: Penn Valley, California, USA
Posts: 2,407
Thanks: 2
Thanked 827 Times in 577 Posts
Default Re: Kohler 10ROY, AVR G-278598 Failure - Universal AVR Replacement?

If the Q thing is a problem I have not seen it. I have installed my Chinese "test" regulator on lots of (mostly low ohm Kohler) generators in order to prove they are not broken and never observed any oscillation. I would take this on a case-by-case basis.

Of course if a unit is way out in the woods and hard to access, I am installing OE no matter how much it costs.
Reply With Quote
  #13  
Old 02-15-2019, 05:27:16 PM
Zephyr7 Zephyr7 is offline
Registered-III
 
Join Date: Mar 2017
Location: Davisburg, Michigan
Posts: 1,979
Thanks: 605
Thanked 1,116 Times in 761 Posts
Default Re: Kohler 10ROY, AVR G-278598 Failure - Universal AVR Replacement?

Iíve never seen it either, but I like to play it safe. My guess is how much of a risk you take depends a lot on the specific peculiarities of the particular genset you happen to be working on. Resistors are cheap insurance.

Bill
Reply With Quote
  #14  
Old 02-21-2019, 03:13:05 PM
TC25D TC25D is offline
Registered
 
Join Date: Dec 2013
Location: Saukville, Wisconsin
Posts: 10
Thanks: 0
Thanked 1 Time in 1 Post
Default Re: Kohler 10ROY, AVR G-278598 Failure - Universal AVR Replacement?

Ok, I promised to come back to the forum with my update.

1) I installed the AVR from Flight Systems. It is their P/N 72-278598-00.
2) It was an exact fit. Same connector, same form factor, same mounting holes.
3) It is gel protected but repairable by Flight Systems.
4) If someone ever wanted to go to the original Kohler part they could (assuming Kohler still has the AVR).
5) The unit I installed was a Flight Systems pre-production unit but it works perfectly!
6) The unit was packed nicely and came with an instruction sheet. I performed the checks, had to replace a blown power supply fuse for the AVR (10A ceramic fast blow) but other than that everything works perfectly. I assume the fuse cleared when the old AVR blew.
7) I measured the house voltage across the grid. It was 123.8VAC between neutral and L1 and L2 - this was with lights and furnace running.
8) I switched to Gen power using my ATS and the voltage was about 125VAC.
9) with a meter plugged in the wall (having my wife participate) I asked her to tell me over the cell phone what the reading was. With a few tweeks and the same load I set the V adjustment on the AVR to hit exactly 123.8VAC
10) Under the same loads I adjusted the Stability pot. turned down til I saw bouncing on the meter then returned it to a just hitting the stable condition.

This was an easy install, took about 30 min. I realized that the 240VAC gen would want 120 per phase but the gen head is rated from 100-130 so I believe my setting is correct and within range. I am open to turn it down. BTW, no load with out of box settings the Flight Systems AVR put the gen at exactly 240.3VAC. I could not believe that. But loaded in went down quite a bit...thats when I decided to match grid power levels while lightly loaded. If anyone feels different...lets start the discussion. It is an easy adjustment.

We live on 6 acres in the country. We have a well, a mound system, sump pumps, etc.. We need power to have water, to flush the toilets, etc.. Being in the country when we lose power they have a tendency to take care of the populated areas first...and we get that. But we need power no matter what.

This diesel genset works great and serves the purpose. Thank you to Flight Systems for providing a solution to the failed AVR. So far, so good! Brian A. at Flight Systems was able to answer all of my questions.
Reply With Quote
The Following User Says Thank You to TC25D For This Post:
  #15  
Old 02-21-2019, 03:56:30 PM
TC25D TC25D is offline
Registered
 
Join Date: Dec 2013
Location: Saukville, Wisconsin
Posts: 10
Thanks: 0
Thanked 1 Time in 1 Post
Default Re: Kohler 10ROY, AVR G-278598 Failure - Universal AVR Replacement?

Click image for larger version

Name:	IMG_8512.jpg
Views:	23
Size:	105.0 KB
ID:	329109

here is the photo of the Flight Systems AVR
Reply With Quote
  #16  
Old 02-21-2019, 05:53:30 PM
TC25D TC25D is offline
Registered
 
Join Date: Dec 2013
Location: Saukville, Wisconsin
Posts: 10
Thanks: 0
Thanked 1 Time in 1 Post
Default Re: Kohler 10ROY, AVR G-278598 Failure - Universal AVR Replacement?

Misc. learnings from fixing this generator issue.
1) I now know that the generator will put out 60VAC without the AVR. Meaning that with no excitation voltage from an AVR it will put out voltage in the amount of about 60VAC per leg. This means that something is creating a field...one person told me it is residual magnetism, another told me it is the battery (wrong, I will explain that next), and another told me the rotor gets magnetized by induction from the stator. Not sure which it is but if the gen is putting out voltage - it is unlikely to be a failed stator or rotor.
2) the start battery connects briefly to the stator at startup...it magnetizes the rotor for an instant (POLARIZES IT TOO) and then is disconnected from the rotor. Maybe this is the source of the residual and sustained magnetism even without the AVR. this happens every time it starts - i can see it in the ladder logic.
3) there is a separate winding in the stator used for power to the AVR. Why? because if the primary winding is effected by a short circuit or by harmonics from a non-linear load...at least the feedback from the separate winding is steady. and why would you want that? in the case of a short circuit that draws a lot of current it could shut down the generator real fast. In fact it could shut it down so fast the fault clearing overloads (circuit breaker downstream..like in your house breaker panel) might not ever trip. Thus, you might have a hard time finding what caused the gen to shut down when you never see a tripped breaker. no tripped breaker then how would you know where to look for the short circuit? If the power supply for the AVR comes from this separate stator winding (auxiliary winding) then the power to the AVR is maintained and it will continue to function exciting the rotor winding to keep the magnetism to allow the stator to produce the necessary voltage and current to trip the downstream breaker. Imagine if the short circuit overload just immediately shut the power off to the AVR collapsing the field preventing enough current and voltage from being produced to actually clear the circuit....that would be confusing. Also by having this separate winding power the AVR it isolates the the AVR power supply from the negative effects of non-linear loads that might be connected to the generator output. An example of a non-linear load would be a variable frequency drive. in the case of a variable frequency drive it has a full wave bridge rectifier and capacitor bank that converts the AC power to the DC that is converted back to variable voltage and frequency on the output. Usually it would be connected to a 3 phase AC squirrel cage induction motor. this conversion of power process will create harmonics and the stator coils on the genny will see them and it could cause issues (instability of the power to the AVR). So, there are many patents on this auxiliary winding and associated circuits that can give this design an advantage over typical designs pulling power off the main stator windings. Probably a better solution is a separate permanent magnet generator on the back of the shaft that can be used for separate power for the AVR. But I am happy with the aux. winding on the stator...it seems good enough.
4) I think the Chinese AVRs could be made to work but their specs are not what is needed for this particular Kohler generator. It seems that they cant put out enough current. I learned that they only need to put out like 45V onto the rotor but the Kohler rotor winding is like 3.5 ohms and the chinese AVRs spec. a min. of 15 ohms. so i went with the smart solution from Flight Systems. It can handle the low ohms and higher current...i guess 3-6 amps. It has a 10 amp fast blow ceramic fuse upstream of the AVR near the circuit breaker...so maybe 9 amps is max....i just don't know.
5) biggest learning i got from this situation is that the AVR if fully potted with hard resin could not be repaired by me...or at least without extraordinary measures. secondly the the part is really expensive...more than $500. and finally the real thing i learned here is that if i had bought another factory unit that is not repairable and something in the gen set caused it to blow, smoke, fail or otherwise go kaput...I would have just created a $500 fuse. I would be holding a brick that likely cant be repaired. I needed a warranty - i got it. I needed a repairable unit. I got it. I needed technical support. I got it. and I needed current production vs old stuff sitting on shelf that may have a defect like the one that blew.

I realize that was alot. but today i fixed my gen and this forum helped me

Thank you to Smokstak forum contributors. Regards, Cliff
Reply With Quote
  #17  
Old 02-24-2019, 07:44:39 PM
TC25D TC25D is offline
Registered
 
Join Date: Dec 2013
Location: Saukville, Wisconsin
Posts: 10
Thanks: 0
Thanked 1 Time in 1 Post
Default Re: Kohler 10ROY, AVR G-278598 Failure - Universal AVR Replacement?

had our first power outage today 2/24/2019. WE Energies here is WI already restored it. It lasted 90 min.. The genny turned on automatically and my family when about their business except the internet. The local repeaters are powered by the grid so Time Warner Cable- now Spectrum went down. but it felt damn good that everything else worked! Including the gas forced air heaters.
Reply With Quote
Reply

Bookmarks


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

F o r u m Jump

Similar Threads Chosen at Random
Thread Thread Starter F o r u m Replies Last Post
Kohler 228605 Kit 278598 Regulator Wanted BrianHaze Kohler Generators 2 09-21-2018 03:14:30 PM
Kohler 10ROY only powering one leg wap Kohler Generators 7 10-01-2014 06:18:56 PM
Kohler 10ROY Brushes? jones09641 Kohler Generators 1 09-27-2013 07:38:46 PM
What is a Kohler 10ROY worth? pmcw Kohler Generators 2 04-27-2011 08:18:39 PM
Kohler 10roy Generator wap Kohler Generators 5 04-08-2009 06:29:19 PM


Use "Ctrl" mouse wheel to change screen size.
All times are GMT -4. The time now is 05:53:34 PM.

Smokstak and Enginads site search!


All use is subject to our TERMS OF SERVICE
SMOKSTAK® is a Registered Trade Mark - A Community of Antique Engine Enthusiasts
Copyright © 2000 - 2019 by Harry Matthews P.O. Box 5612 - Sarasota, FL 34277