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flashing 3 phase generator
6

flashing 3 phase generator

flashing 3 phase generator

(OP)
I'm new to the forum.
I have a Kohler 15RMY62 208V 3 phase 15 KW generator that is producing 30 VAC (rms) at 1800 rpm.

The diodes and brushes have been replaced.

I disconnected the field windings from each other and they are 0.9 ohms each. The wiring has no visible signs of burning or discoloration.

I flashed the 4 pole rotor with a 12VDC battery thru the brushes when it was not running. No change.

Any help or advice would be most appreciated!

RE: flashing 3 phase generator

Some generators need a load before they put out more than a few volts.  Have you hooked the ol'waffle iron up and tried it?

Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com

RE: flashing 3 phase generator

(OP)
Thanks itsmoked!
 I haven't tried hooking up a load.
Waffle iron? OK, I'll try it!
Thanks!

RE: flashing 3 phase generator

(OP)
I connected a 13 ohm nichrome resistor across 1 leg to neutral. Same thing as before, 30 Vrms, 64.4 Hz. Scoped out as a good sine wave.
Could this be a voltage regulator problem? Does the rotor need to be flashed with higher voltage?

Again, any help/advice is very much appreciated!

RE: flashing 3 phase generator

Shucks I had a gen that put out about 25Vac until you dropped a load on it then 'bang' 120Vac.

Generally if you are getting 30V there is more than enough energy available to allow the generator to 'build' up to normal.

Yes it could absolutely be the VR.  Generally that is where the problem lies.

First though you said 'rings' these are for the field then?

  If that is so you may be able to provide some 'manual' field current and see the output rise.  If you can and you see it rise dramatically never mind to 208V then you can probably assume the field is intact and the 'mechanical' generator is okay.  At this point you would want to focus on the regulator.  Again the regulator's job is to look at the output voltage and adjust the field current accordingly. If you could put an ammeter of some sort in the field circuit you could see if the VR was functioning.  Make sure your ammeter is good for several amps. (DC)

Others will come along who sleep and eat generators.  They will have some sage advice.

Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com

RE: flashing 3 phase generator

(OP)
Are you refering to a capacitor/inductor resonation? Can't find a cap anywhere except on a VR board in the unit.
  "If that is so you may be able to provide some 'manual' field current and see the output rise."
I'm not sure exactly what you mean. 12 volt battery flash to the field windings and watch the ammeter? If it works, the voltage would go high in several milliseconds. I'm allergic to sulfuric acid, so I'll fuse the battery. :)
Thanks


RE: flashing 3 phase generator

"Are you referring to a capacitor/inductor resonation?"

You totally lost me here.. Capacitor?

I am talking about providing field current with something.  Disconnect the VR and just feed current to the field.  A battery might work but you might need more than 12V.

I'm also talking about finding your existing system's field control wires to/from rings and inserting an ammeter in one.  You should see some amps being provided by the VR.

Of course before this stuff with all power removed you should be able to confirm the field wining is not open. (Presuming you've already done this!)

Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com

RE: flashing 3 phase generator

To avoid repeating a bunch of issues, please read this older thread: thread659-117376

Being that yours does have brushes we can assume that you have a synchronous generator, which makes sense since you are expecting to run it in island mode. OK then, did you realize that a synchronous generator must have power applied to the exciter at all times? Flashing is just to set up an initial field on a brand new generator or one that has been out of service for a long time where the residual magnetism in the rotor is insufficient to provide enough power to the exciter system, and is usually done off of the same battery used to start the engine. In fact, the initial flashing on most small portables can be done with very little voltage, I have done it with a drill motor as a generator in a pinch (I won't go into details unless asked). After that the exciter circuit needs to take over on its own.

The 30V output you are getting is likely the result of some small amount of residual magnetism in the rotor. The fact that it can do that means you should have enough to get the exciter going. Is your exciter properly connected? You mentioned having replaced the diodes, are you sure all the wires went back onto the same terminals? Now that I think of it, why did you have to replace the diodes anyway? If they shorted, chances are some other part of the circuit was damaged as well. Does it have an output? Does it have a Field Circuit Breaker that may be open?

Eng-Tips: Help for your job, not for your homework  Read FAQ731-376

RE: flashing 3 phase generator

holo,

  You need to answer jraef's questions above to yourself in your troubleshooting process.  Also, not being real familiar with Kohler model #'s, I don't know how old it is--how advanced of a voltage regulating system it has.

  To do a conclusive flash while it is running, identify F1 an F2 wires going to the excitor. This is where you want to flash the DC in.  If running a solid state regulator, you want to disconnect the leads from the regulator before doing this, or put a diode on the B+ line before flashing to avoid sparking surprises.

  If you've confirmed diode installation/brushes/wiring to them is good, and flashing gives you a predicted result, investigate the regulation circuit it has.  Check if sensing/power voltages are rising/falling when being flashed.

  Any number of things it could be on these old small units.    Just need to identify the key components, look for expected results from each, and lots of ohming to ensure all is connected from point to point.  

RE: flashing 3 phase generator

3
Hi folks;
First, if you try to flash the generator with the starting battery before you disconnect the voltage regulator, you will probably join a long list of people with blown voltage regulators.
But, your generator should boot up with 30 volts. It's when we are reading between zero and 3 or 4 volts that we consider flashing.
If you disconnect the voltage regulator you may connect the starting battery to the field.
Usually it takes 12 to 24 volts on the field to get full voltage at no load. It often takes twice as much voltage on the field to give full voltage with full load.
by the way, I have succsesfully flashed a 35 kw set with a 1.5 volt "D" cell in series with the voltage regulator. It doesn't take much. (The voltage regulator probably helped a little.)
It sounds as if you have regulator problems.
respectfully

RE: flashing 3 phase generator

If you get 30 V residual voltage, no need to flash the field. Either your field circuit is open (you mentioned "I disconnected the field windings from each other" - did you connect them back ? or your leads from the excitation circuit to the brushes is broken) or your excitation system or voltage regulator has failed.

* If a little knowledge is dangerous, then I am the safest person in the world *

RE: flashing 3 phase generator

The field flashing procedure isn't for the sole purpose of restoring residual.  It can be used as a troubleshooting method of testing the integrity of generating side of the machine.  No point in throwing new voltage regulators at it if something else is dragging it down.

RE: flashing 3 phase generator

I would think that if you only have .9 ohm across the fields you have a problem with the field windings.  .9 ohms is far too low for the Kohler.  Check further for shorted windings.  6v on the fields ( with the avr out of the circuit) should bring the output to well over 100volts.  But ohm's law indicates that if you apply 30 volts on a .9 0hm field you would be drawing 33 amps, far too much.  You have a problem with the fields or the leads to the fields.  

RE: flashing 3 phase generator

I just reread the post and was going to suggest that the field resistance was too low, but JIMGEN beat me to it.
Good call JIMGEN.
respectfully

RE: flashing 3 phase generator


OP said all 4 pole coils measure 0.9 ohms each. That gives a total  of 3.6 ohms with 8.33 amps field current.

Given the equal resistances of the 4 pole coils, I would rule out any turn shorts.

The turn short can also be confirmed by doing ac pole drop test. (Apply 110 V AC across field winding terminals and measure the voltage drop across each pole coil. Equal voltage drops will rules out turn shorts)

* If a little knowledge is dangerous, then I am the safest person in the world *

RE: flashing 3 phase generator

Good point edison123;
A very common but by no means universal specification for voltage regulators for small generators is Minimum 16 ohms field resistance.
If the field is good, it is possible that the voltage regulator has been replaced with one which requires a minimum of 16 ohms.
respectfully

RE: flashing 3 phase generator

(OP)
I purchased a new AVR and voltage regulator. No change in the output voltage, even with the waffle iron.
The rotor checked out at 27 ohms. My book for single phase unit shows the reading should be between 2.5 and 4.5 ohms. This sounds too low.  I'm guessing it should be the same for three phase because both operate on DC voltage to the exciter rings.
With the electronics disconnected and the rotor hooked to a 12 volt auto battery, I get 46 volts out. Can't get the ammeter to work. There does not appear to be a short in the rotor.
Your help is greatly appreciated!

RE: flashing 3 phase generator


High rotor resistance (27 ohms as against 3.6 ohms) indicates some high resistance connection either in between poles and or in the rotor leads.

* If a little knowledge is dangerous, then I am the safest person in the world *

RE: flashing 3 phase generator


ed,

"The turn short can also be confirmed by doing ac pole drop test. (Apply 110 V AC across field winding terminals and measure the voltage drop across each pole coil. Equal voltage drops will rules out turn shorts)"
 Voltage drop  across each pole should not necessarily equal. It should fall within tolerance value.

holo,
 Better send your generator for thorough check up if you desperately need it.  

RE: flashing 3 phase generator

Hello;
I did some googling on your model number. I found some of your other queries and got a little new information.
Apparently, your generator has a static exciter. This is not common on a set this size. The only other one I have seen was an old Caterpillar.
A static exciter may have the voltage regulator built in, or it may be basically a power amplifier controlled by a standard voltage regulator.
Voltage regulators for that size set are pretty generic and/or interchangeable.
HOWEVER, a standard, off the shelf AVR (automatic voltage regulator) will not have the current capacity to properly energise your field directly.
From the field resistance values you have supplied, and the voltages you found when testing, I strongly suspect that your problem lies in the static exciter.
You will need 31 volts in to get 120 volts out at no load. possibly twice that at full load. You will need close to 20 amps.
The 27 ohms is a worry. You should measure the rotor resistance at the slip rings and NOT through the brushes. There will be a non linear voltage drop across the brushes that will cause serious errors if you try to measure field resistance through the brushes with a multi-meter.
One other thing to check is the connections of the output or power leads. This is a long shot but it is something that should be verified.
For a DC supply you may use batteries. 6 volts, 12 volts, 24 volts, etc. The output voltage should be proportional to the input voltage.
You may also use a variable AC source and a bridge rectifier. The relatively large inductance of the field winding will act as a quite efficient filter.
respectfully

RE: flashing 3 phase generator

(OP)
waross, the 27 ohms were from the sliprings. Sorry, I should have made it clearer. No continuity between the slip rings and the rotor shaft or to the case.
The new voltage regulator and AVR board are from Kohler.
Here's a link with pics of the electronics. http://www.fieldlines.com/story/2006/7/3/202447/2073
The boards and regulator have since been replaced and everything inside the box cleaned. All connections were unplugged and replugged.
I'll try varying the voltage and hopefully varying the amps also.
Thanks for the help!

RE: flashing 3 phase generator

Hi holo;
I'm curious, and I may have missed something.
At one point I understood that the field resistance was 0.9 ohms X 4 = 3.6 ohms. This would be consistent with a rotary exciter, either with brushes or brushless.
At another point I understood the resistance to be 27 ohms.
This would be consistent with the field of a rotary exciter.
I don't believe that you have a rotary exciter.
However, despite the large manufacturers of generator ends more or less using the same values now, anything that works is possible with generators, particularly old generators or lessor known makes. In this case Kohler is well known so we would be looking at old.
If you have replaced the AVR with a Kohler replacement and the machine still doesn't work, there are two things to check.
1> When you changed the AVR, was there an electronic module connected between the output of the AVR and the brushes? If so it would be the static exciter. It should be checked or replaced if present. If possible verify with Kohler whether or not the machine uses a static exciter or if the AVR connects directly top the field.
2> Identify the power windings (1 to 4, 2 to 5, 3 to 6, 7 to 10, 8 to 10 or 11, 9 to 10 or 12.) depending on whether it is a 10 lead or a 12 lead machine. Check each individual winding for shorts or grounds. Then with battery excitation, check that each winding is developing the same voltage. This will give you a double check on the condition of the stator windings.

Double check also the RPMs and/or frequency.
Your machine shoukld be turning 1800 RPM.
respectfully

RE: flashing 3 phase generator

If the measurement is being made using a multimeter, the carbon brushes will be giving incorrect measurement results because of the low applied voltage. How are you making the measurement?

The boards you replaced - are they the ones which are covered in a thick layer of dust or sediment? Are other parts of the controller in a similar condition? If so, a good clean may be a useful starting point. Electronic circuits can do wierd things if a vaguely conductive contaminant is present in a high impedance or high voltage part of the board.

----------------------------------
  I don't suffer from insanity. I enjoy it...

RE: flashing 3 phase generator

Sorry, correction/clarification;

Quote:

At one point I understood that the field resistance was 0.9 ohms X 4 = 3.6 ohms. This would be consistent with a rotary exciter, either with brushes or brushless.
Should be,
That would be consistent with the main field coil winding, not the field of a rotary exciter.
That is the point of an exciter. The voltage regulator usually does not have the power available to excite the field directly. The AVR controls and excites the exciter and the exciter excites the main field.
I would expect the main field to have about 3 or 4 ohms resistance. I would expect the exciter field to have about 27 ohms resistance (more than 16 in any case).
There are exceptions and I suspect that your machine may be an exception.
It doesn't have a rotary exciter. If the field resistance is

Quote:

I disconnected the field windings from each other and they are 0.9 ohms each. The wiring has no visible signs of burning or discoloration.
Then you either need a static exciter or a non-standard voltage regulator.
If the field resistance is 27 ohms the problem may be in the main windings, the wrong rotor may be installed, the speed may be slow, the air gap may be excessive, kohler may have supplied the wrong AVR, or other problems.
respectfully

RE: flashing 3 phase generator

(OP)
The field resistance was measured at 0.9 ohms by checking the start and end of each winding after the leads were disconnected from each other.

The resistance measured through the slip rings, with the brushes and holders removed, was 27 ohms. I will check the voltage between each lead today.

My Fluke meter is showing about 64 Hz on the output. Since it's a 4 pole unit, I am assuming the rpm's are around 1800. :)

The entire unit was covered in contamination.
I cleaned all the the wiring, connections and original boards. The kill switches were also disconnected to eliminate them from the equation.

Once again, thanks for your comments!

RE: flashing 3 phase generator

By field resistance do you mean the rotating field or the stator. Something is not adding up here. The rotating field has four poles. Four times 0.9 ohms is 3.6 ohms, not 27 ohms.
We usually call the stator windings on your type of genset the main windings or the power windings. When you say field windings, we think of the windings on the rotor.
respectfully

RE: flashing 3 phase generator

(OP)
"The rotating field has four poles." This has 27 ohms across the slip rings without brushes.

"We usually call the stator windings on your type of genset the main windings or the power windings." The main windings are 0.9 ohms. 12 wire main winding.
Sorry for the confusion.

RE: flashing 3 phase generator

Holo, have you checked what the voltage is across the sliprings, when everything is running in the normal wiring setup?
Have you checked the current through the slip ring circuit when everything is running in the normal wiring setup?
You have previously mentioned that with standard setup, you get 30vac, and if you apply 12V to the field, you get 46Vac.
It seems to me that your AVR is probably not giving any, or very little field current, for some reason.

RE: flashing 3 phase generator

I agree with DaveScott;
It is starting to look as if you have an AVR problem. Check for brushes sticking, loose or broken pigtail leads on the brushes, surface contamination on the slip rings, and anything else you can think of that may introduce resistance into the circuit from the AVR to the field. If this is an old machine, check the wires. There may be internal corrosion in the wiring to and from the AVR.
Check the output of the AVR. 63 volts is a common maximum voltage for a small AVR. You may have to load the output with a 60 watt or 100 watt light bulb to get a good voltage reading.
respectfully

RE: flashing 3 phase generator

(OP)
I think I may have found the problem, or at least one. V7 and V8 wires, which are from the generator powers the AVR. Both are putting out intermittant voltage readings. Looks like it's time to take the generator apart and look.
This is going to take a few days.

Thank all for the comments! This has been quite a learning experience.

RE: flashing 3 phase generator

Hello from another new member prompted by this thread.  I too am several weeks in to troubleshooting the exact same Kohler generator 15RMY62 prob from  70’s-early 80’s that came with the house I just moved into, worked OK for a year then started blowing reset switches, I have decent small electronic skills, and helpful pals and initially diagnosed dysfunctional VR board  (B-258296) which combines the SCR module and Voltage regulation on one board. Replacement is $570 so am in process of rebuilding the old one, highest failure parts first, I can replace every part for less than $100, although some of the values are a bit tricky to determine. I have briefly had it working 100% then re-failed am in to the next layer of relays and connectors, already did the basic rotor/stator checks.
The route of my evil was layers of mouse doo-doo and urine. Its amazing this (conformally coated) board lasted as long as it did!
Anyway, I have the Kohler book on this model including coil and control wiring,and some trouble shooting, if you need it, I can copy the pertinent bits, but this does NOT sadly include a schematic of the VR board, which I would love to have if anyone has it. It is Not available from any Kohler dealer even the usually helpful Buckeye folks, they just don’t have it. Sort of an OEM part.  So I will probably have to reverse engineer the board, but that would not give me definite component values on those with markings eroded by rat wee-wee. Anyway I will try to help if I can, though am not (yet :) ) a generator specialist, and may ask for advice also. It is definitely a "static" excitation of field, it has a relay to "self flash" on start up but it is not clear if it really needs it, 30V is denitely what you get with unexcited (residual) rotor field. Keep us posted Holo. Oh yeah, mine is pre-wired for single phase operation, both 120 and 240. (V9 disconnected, internally wired armatures for single phase. )

RE: flashing 3 phase generator

(OP)
Hello Allodola,
I now have a manual coming from Kohler. It probably does not show the board schematics. I have a few pics of the cleaned board that shows every part except one chip. If you need them, let me know. They are ~1.5 mb each.

What's your ohms reading across the sliprings and power windings?

RE: flashing 3 phase generator

These are 12 lead generators.
12 lead machines are easily converted to single phase. V9 should be connected and there is no internal wiring unless it has been rewound and changed from the original.
You lose 1/3 of the KVA, but the KW will equal the (New) KVA.
Power factor rating will be 100%

EG. Three phase ratings:
15 KW
18.75 KVA
80% PF
Same machine, single phase;
12.5 KVA
12.5 KW
100% PF

For a machine that is originally rated at 100% PF.
15 KVA
15 KW
100% PF
Same machine, single phase;
10 KVA
10 KW
100% PF
respectfully

RE: flashing 3 phase generator

Waross, you are correct, thanks for the clarification. The "book" has V9 disconnected from the VR board bus, presumably not needed for the Voltage reg function, but is in circuit as an armature. The "internal" wiring I mentioned really referred to the configuration of the 12 leads into that single phase set up that is niether Wye nor Delta (whats it called?), it is internal only in the sense it is "inside the box"!
Holo, is your board the one with the SCR units and heat sinks all on the one board with the rest of the VR? If so I would love to see the pictures, might help me clarify a few things. Thanks. I will be going deeper into my unit as soon as I get a lightning free evening! I'll see if I jotted down thr resistance measurements or re check them for you.

RE: flashing 3 phase generator

The single phase connection is called a "zig-zag" connection. Not to be confused with the transformer of the same name.
Another connection that is becomming common in newer sets to supply single phase from a three phase machine is the double delta connection.
The double delta is a symetrical connection.
If I have to convert a three phase machine to single phase, I use the double delta if the leads are well numbered. All the leads must be accurately identified when changing to the double delta.
On an older machine, where there may be some doubt about the lead numbereing for any reason, I use the Zig-zag connection.
The windings may be identified and the final connection checked with a multi meter, even if the numbering has been lost, when changing to the zig-zag connection.
Both connections have been used by the major manufacturers. I am not aware of any difference in the end result. Both connections work well.
respectfully

RE: flashing 3 phase generator

(OP)
Allodola, a few pics of the dirty boards are listed in a url earlier in this post. :) You can see if that's what you need. If it is, I'll figure out how to post the clean ones.

warcross, I understand the zig-zag. How is the double delta wired? What are the advantages of double delta vs. zig-zag? Nothing from Google.
Where should V9 be connected?

My generator seemed to be wired in 208 3 phase open delta. Presumably, it was being used in place of a single phase 240v circuit. Anyway, It's wired single phase now.

RE: flashing 3 phase generator

Holo, your set up is identical to mine except you have the seperate "SCR module" (The thing on the side with the red disc Varistor that looks like a capacitor.) So prob not worth the effort to upload the board pic. BTW the Electronics including the control mechanisms/overload resets are much more vulnerable in general than the generator itself, so I would really make sure your board is capable of puting out F1 and F2 to the field, Make sure the Voltage/overcrank rset switches are in correct position, not shorted or needing to be reset, crud can even mess up the mechanics of the toggle switch  action. On re-read you did say you got a NEW VR. did it include a new SCR module (is that what you meant by the diodes" were replaced?

RE: flashing 3 phase generator

(OP)
Yes, the VR is new and so is the bridge rectifier diode that's connected to F1 & F2.(far side of the pics mounted to the wall.)
The relays in the foreground are not new. They seem to function correctly. I've switched their positions without any change in voltage.

RE: flashing 3 phase generator

Well, relays are pretty tough. I was talking about the stuff in the box with the meters and the reset switches. At one point, you mentioned "disconnecting" some of the "kill switches". Those might be part of the correct operating of the relays, i.e. the thermal time out switch for overcrank etc has an open and a closed set of connections. Ain't this critter fun?

RE: flashing 3 phase generator

(OP)
Allodola, I disconnected the kill switches for the external engine circuits. I think they all short to ground. Might be the case. I'll hook up one at a time and see what happens.

RE: flashing 3 phase generator

I took apart each relay this weekend, carefully pulling the plastic covers (with board removed in shop)Several of the contacts had green copper oxidation which I sprayed with contact cleaner. Also, note the four are NOT identical. 3 are 12V D/C coils, but one "1CR" on my unit, is a high voltage AC coil with a "normal" coil resistance of 1700 ohms. (The D/C units have coil reistance of about 100 ohms)
Just FYI. I'm in the laborious stage of reverse engineering the board now. best.

RE: flashing 3 phase generator

(OP)
Oops, I have probably reversed them. Thanks for the info.

RE: flashing 3 phase generator

Sure. Here's another lesson (for me), though odds are small it has anything to do with your "issues". When I initally checked the coils I measured inside the relay box, as I had the plastic covers off, to look for contact crud. The coils measured appropriately. BUT, when one (CC) still seemd dysfunctional, I went back and checked from the circuitboard traces (after scraping off plastic coating) and lo-and-behold, continuity was broken from one coil end through the board to the trace! No end to the way things can fail.

RE: flashing 3 phase generator

Hi folks:
Sorry for the delay getting back, but I had a great weekend.
Re., Zig-Zag connection vs. Double Delta;
On one of the pictures that was posted of your generator, there was a diagram of the zig-zag connection for single phase.
This site has a diagram of a double delta connection.
http://www.friesen.com/manuals/generator_wiring_diagrams.asp

The site also has a chart crossing the metric numbering convention to NEMA numbering convention.

I have seen a lot of various problems with a lot of generators.
I have never seen a problem that could be solved by changing from DD to ZZ or ZZ to DD.
DD is symetrical, and ZZ is not symetrical, but in practice, I have not observed any difference.
ZZ was used for years by many major manufacturers, DD is now becoming more common.
It may at first appear intuitively that the side with the two windings may have greater voltage drop, but a vector addition of the voltage drop shows it to be equal to the single side.
The main difference I see is that on an old set, with damaged or missing wire marking, the ZZ may be changed from 1 Ph. to 3 Ph. or from 3 Ph. to 1 Ph. quicker and with less chance of mistake, than the DD.
With appologies to the EU folk, virtually all the sets in the NEMA world start with three phase star connections.
If a set arrived from the factory wired for 3 Ph. delta, it may be easier to convert to DD than to ZZ.
By easier, I refer to the number of connections that have to be opened and reconnected.
respectfully

RE: flashing 3 phase generator

Hi again:
The relays are usually for automatic starting and motor protection. Although this is important, the relays seldom affect the generator.
The exception is on old sets that may have a "flashing" relay. A flashing relay will be interconnected to the Automatic Voltage Regulator.
respectfully

RE: flashing 3 phase generator

Thanks for the info. In the Kohler Holo and I are working on, one of the relays is in fact set up to flash the coil with 12V, but perhaps more importantly, the others in the start up sequence are tied in with a "shut down relay" which will disable the Voltage regulator. Of course if the SDR itself is dysfunctinal it may not provide its over voltage and other protective functions, allowing vr board chips to be damaged. I think also that increasing contact resistance and or intermitant contact/arcing might be generating voltage spikes from the relay that are capable of getting into the VR. Things are so interconnected that it would be hard, though certainly possible, to get the engine up and running AND the VR circuit properly functioning without the 5 control relays and the thermistor type "time out" switch (which has multiple functions) in working action. It's not clear it's a particularly good system.

RE: flashing 3 phase generator

Hello holo and Allodola;
I am sorry for the delay, I've been short of time the last couple of days.
Allodola has just supplied the missing piece of the puzzle.
I am not surprised to see 30 volts out if the relay is flashing the field with 12 volts.
For some reason, your flashing relay is not transfering control to the Automatic voltage regulator.
What you are refering to as the shutdown relay is probably an AVR control relay.
In many of the older sets the AVR did not have an "Under Frequency Roll Off" feature. (UFRO)
Without the UFRO feature, the regulators would fail in a matter of a few minutes if the engine was operated at reduced speed.
It was recomended on many sets that the voltage regulator not be turned on until the engine was up to speed and that the voltage regulator be turned off before stopping the engine.
A shut-down relay connected to the AVR would not be unexpected on an old machine. The shutdown relay may be frequency dependent. if an old capacitor has failed or is failing the relay may not be functioning properly.
Note: I say may. There is not a lot of standardization from one make to another on the old generators in that size range.
AVRs with UFRO usually have a setting for 50 Hz. or 60 Hz.
Often it is jumper selectable.
I hope this helps.
respectfully

RE: flashing 3 phase generator

Just an update on my experiences. Finally gave up trying to repair my rat urine damaged VR board. Did replace several relays and sockets on the seperate "buss" board with parts from Mouser. Found a helpful chap named Dennis at "ASAP" (www.partsfortechs.com) who supplied a simple but rugged aftermarket VR (208-240 in for up to 120V DC out to field) for about 300$ total. Gen Set now works fine. It does NOT have built in over voltage protection, and I am debating adding an external relay to the input of the VR board.
Also pondering the necessity of a Propane leak detector in the housing containg the Gen set, electronics and 20 year old 4 cylinder LP Wisonsin engine. Any thoughts on this?
Allodola

RE: flashing 3 phase generator

(OP)
Hi Allodola,
I have also delt with ASAP. They are very helpful and their original Kohler parts are cheaper than the dealers.

Instead of using an overvoltage relay, could you use an MOV? www.digikey.com has them for cheap.


RE: flashing 3 phase generator

Hi Holo- MOV's and the like are worth considering, but they short when over volts, and even well fused I am reluctant to short out my V7-V8 winding! There are some commercial products for 35-100 dollars that have variable voltage and timing adjusts that throw a SPDT relay when sensing over voltage,that I could use to open the field winding or even turn off the engine. In the ORIGINAL iteration of my Kohler there was an overvolt sensor tied into the "SDR" shut down relay on the Voltage Reg board, but this did not exist in the (Kohler supplied) "up dated" VR that was in the set when I got it and eventually died.  The newest aftermarket VR seems quite hardy and well made, but I like the idea of not toasting my well pump just when I need it most...
Am certainly open to suggestions of an easy reliable protection approach. Ciao

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