Author Topic: Flashing an Alternator help request  (Read 1559 times)

Johndoh

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Flashing an Alternator help request
« on: May 24, 2018, 09:54:49 PM »
Does anyone have an idiots guide to flashing a generator alternator? Thank you
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dieselgman

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Re: Flashing an Alternator help request
« Reply #1 on: May 24, 2018, 10:27:29 PM »
Each generator type will have specific instructions and they are variable depending on the specific design.

In general you have to apply a low voltage (6vdc) to your field windings to get the magnetism back. Once you have kick started the process, it will be self maintaining. If there is an AVR involved, you will need to remove it from the circuit during the flash to avoid damage. If your unit is "inherently regulated" as in Marathon LIMA MAC models, all you will need to do is momentarily short circuit the output windings while the unit is spun up to speed. Exact procedures are usually covered in the O&M manuals for your generator head.

If unfamiliar with the risks and the process,, get some help. Test your windings and components while you are at it.

dieselgman
« Last Edit: May 24, 2018, 10:33:14 PM by dieselgman »
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glort

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Re: Flashing an Alternator help request
« Reply #2 on: May 24, 2018, 10:56:50 PM »

I always did it from a 12V battery with the AVR but no loads connected. Maybe I was lucky?

Did do it while it was running though. Generally with a volt meter on the output you will see the voltage building over a few seconds and then it will come up.
I can always tell when the field has been restored by the electrical hum that I can somehow manage to hear over the clatter of the engines.  Petrols are harder to hear than diesels, must be the respective Frequencys.

What I have also done ( this is a confession NOT a recommendation) is just give the things some real big revs. That seems to create stronger fields with whatever magnetism there is left ( logically) and many times I have got away with that.
I had a genny that would always  be dead after I brought it out after a few months but warming it up and bypassing the governor on the carb to give it a few big hits always brought the thing back to life with no other tinkering required.

Johndoh

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Re: Flashing an Alternator help request
« Reply #3 on: May 24, 2018, 11:12:24 PM »
Each generator type will have specific instructions and they are variable depending on the specific design.

In general you have to apply a low voltage (6vdc) to your field windings to get the magnetism back. Once you have kick started the process, it will be self maintaining. If there is an AVR involved, you will need to remove it from the circuit during the flash to avoid damage. If your unit is "inherently regulated" as in Marathon LIMA MAC models, all you will need to do is momentarily short circuit the output windings while the unit is spun up to speed. Exact procedures are usually covered in the O&M manuals for your generator head.

If unfamiliar with the risks and the process,, get some help. Test your windings and components while you are at it.

dieselgman
So I disconnect the AVR and apply voltage to the wires connected to the coils? Do I do this with the engine running? Do I need to disconnect and isolate the coils prior to flashing?
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Johndoh

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Re: Flashing an Alternator help request
« Reply #4 on: May 24, 2018, 11:14:17 PM »

I always did it from a 12V battery with the AVR but no loads connected. Maybe I was lucky?

Did do it while it was running though. Generally with a volt meter on the output you will see the voltage building over a few seconds and then it will come up.
I can always tell when the field has been restored by the electrical hum that I can somehow manage to hear over the clatter of the engines.  Petrols are harder to hear than diesels, must be the respective Frequencys.

What I have also done ( this is a confession NOT a recommendation) is just give the things some real big revs. That seems to create stronger fields with whatever magnetism there is left ( logically) and many times I have got away with that.
I had a genny that would always  be dead after I brought it out after a few months but warming it up and bypassing the governor on the carb to give it a few big hits always brought the thing back to life with no other tinkering required.
How do I know where to connect each wire? there are 4 in total... IDIOT doing this mr Glort
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dieselgman

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Re: Flashing an Alternator help request
« Reply #5 on: May 25, 2018, 02:15:54 AM »
Lacking the information on what generator head you have installed, exacting instructions cannot be determined. If you have an AVR on your unit, then disconnect F+ and F-, pay close attention to polarity and apply battery voltage here (to the leads going back to your windings) Not to the AVR. Be certain that you do not reverse polarity! I generally start with a 6 volt dry-cell battery and just apply that voltage for a short time without rotation of the generator. In some cases this will restore enough magnetism to start the head the next time it is run and this provides the maximum level of safety for your components and yourself. On sets with no AVR, you will need to apply the same DC voltage to the same portion of your windings, but the wiring is different and will require specific knowledge of your connections. You DO NOT do this to the main generator windings and NOT during operation of the machine. The only exception I know for sure will be the brushless Marathon "inherently regulated" heads. Most modern heads have AVRs or other feedback devices (capacitors or transformers) used to vary the excitation voltage.
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glort

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Re: Flashing an Alternator help request
« Reply #6 on: May 25, 2018, 02:32:48 AM »
If You have a meter, Check for continuity ( Linked wires) and give them a hit. You shouldn't have to do each winding, once you get one up should be enough to energize the others. In any case, you can give them all a lick in succession. You want to see some sparks off the wires you are shorting. If you suddenly get big sparks, stop, you are there already.

After you give each coil a tickle check your volt meter if you can't hook it in while you are doing it.  I'm not really sure how you would check if the thing has come up without the avr connected because that controls the current feed but check on the output of the coils. Not sure what you should see but it will be something. Hook the avr back up give, it a run ( with a few decent revs if you can)  then plug something in. After you put the AVR back on, I would wait and let it run unloaded because sometimes they do take a bit to build  critical voltage and then power up and stabilise .
30 sec-minute should do it well and truly.  If you load the thing too quick you could crash the fields again and have to start from scratch.

You can check the output at the socket with your meter though. If you see the numbers you want, all good to go.

You can try  flashing all the wires, you can't do anything wrong or hurt them. They are all the same, you just want to find a pair.

My technical description may be a little incorrect in the terminologys.
I'm far more hands on and know what to look for than educated enough to know the right terms and names of things but that is the gist of it. 

EDIT:
Just saw dieselmans response.  Different to the way I have always done it but I bow to his superior knowledge. 
Guess if his way don't work, you can try mine, carefully!  :0)
If neither work, then you will need an AVR or have the thing checked out properly.

mike90045

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Re: Flashing an Alternator help request
« Reply #7 on: May 25, 2018, 06:01:38 AM »
when you get it working, never leave a load connected when shutting down, that's one way to de-mag the rotor

Johndoh

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Re: Flashing an Alternator help request
« Reply #8 on: May 25, 2018, 08:34:28 AM »
Thanks guys I will play around with it today. I have other generators and thanks to mr Glort am on the way to building a low speed 12v system as well but a Yanmar generator for 50 appeals to me. I know I could sell the engine on it's own for 8-10 times what I paid for it but where's the fun in that? A new 5 Kv brushless AVR alternator is 400 again no fun in that either!
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Johndoh

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Re: Flashing an Alternator help request
« Reply #9 on: May 25, 2018, 10:03:21 AM »
I have tried to flash the generator with no result I connected a volt meter and it's showing 4 volts however if I connect the battery to F1 and F2 red and black wires the voltages rises and then falls back. Could it be the AVR? If I'm getting 4 volts does that mean it's producing power and doesnt require further flashing? There is no power at the brushes I'd have expected a few volts there??? I wish Id have went to school on days like this!
« Last Edit: May 25, 2018, 10:50:53 AM by Johndoh »
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glort

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Re: Flashing an Alternator help request
« Reply #10 on: May 25, 2018, 11:46:28 AM »

You are getting 4 Volts at the outlet?

EdDee

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Re: Flashing an Alternator help request
« Reply #11 on: May 25, 2018, 02:00:56 PM »
Hi JD,

The brushes are the input to the system to "assist excite" the rotor/armature - There is a feedback from one of the field windings to the AVR that gets rectified and pushed back into the rotor to get the output voltage to spec. It defs looks like the AVR is at fault/suspect here, juice the brushes with about 12VDC nominal and check your output terminal voltages, if they are LOWER than rated, you are fairly safe to continue. Then check any additional inputs into the AVR, there are usually at least one, sometimes two or even three pairs of wires coming back to it. If there are no voltages coming in to the AVR, shut down the unit and disconnect the AVR completely and try again. Still no voltages, then you might have lost or burnt one of the windings. If there are voltages present, above 20V nominally that is, then there is pretty much a certainty that the AVR itself is fried, a common occurrence....

In my limited experience with these creatures, the voltages to/from the AVR/Connectors are
(a) a "driver" output from the windings going into the AVR that gets regulated and fed back to the brushes to maintain output voltage
(b) a "sensing" voltage that is of fairly low current to power the AVR and used to "sense" the output of the main terminals for a control of the output voltage
(c) The regulated output from the AVR which goes to the brushes derived largely from (a)

Note: some AVR's have 2, 4 or 6 wires input as well as the 2 wires out to the brushes...

A brief way I understand them:
2 wire input AVR - a+b above are combined, still has c
4 wire input AVR - as above (most common around my neck of the woods)
6 wire input AVR - as above but sensing and supply are split, still has c - ie 2 sensing wires, 2 supply wires to power AVR, 2 "power wires" to be rectified, regulated and fed back to the brushes via (c)

This is all excluding the 2 or 4 or 6 "output" wires that go to the outside world to run your electrical doo-dahs....

A pertinent question though... with the AVR disconnected, the output wires disconnected and the unit not spinning ie just with the genhead electrically isolated from the rest of the world, have you checked for continuity of the windings and also that none of the windings are shorted to ground? (all winding resistances should be fairly low, in the region of less than 1000 ohms and all windings should have a resistance of greater than 100 000 ohms when measured between coil and chassis.)

If not - time for a re-wind!

Hope this helps

Cheers
Ed
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Johndoh

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Re: Flashing an Alternator help request
« Reply #12 on: May 25, 2018, 03:50:15 PM »

You are getting 4 Volts at the outlet?

Yes on the 230 outlet I don't have a 110 plug
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Johndoh

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Re: Flashing an Alternator help request
« Reply #13 on: May 25, 2018, 03:53:19 PM »
Hi JD,

The brushes are the input to the system to "assist excite" the rotor/armature - There is a feedback from one of the field windings to the AVR that gets rectified and pushed back into the rotor to get the output voltage to spec. It defs looks like the AVR is at fault/suspect here, juice the brushes with about 12VDC nominal and check your output terminal voltages, if they are LOWER than rated, you are fairly safe to continue. Then check any additional inputs into the AVR, there are usually at least one, sometimes two or even three pairs of wires coming back to it. If there are no voltages coming in to the AVR, shut down the unit and disconnect the AVR completely and try again. Still no voltages, then you might have lost or burnt one of the windings. If there are voltages present, above 20V nominally that is, then there is pretty much a certainty that the AVR itself is fried, a common occurrence....

Hope this helps

Cheers
Ed

By lower than rated do you mean lower than 230 or 12 v? Thanka
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Johndoh

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Re: Flashing an Alternator help request
« Reply #14 on: May 25, 2018, 05:08:43 PM »
Hi JD,

The brushes are the input to the system to "assist excite" the rotor/armature - There is a feedback from one of the field windings to the AVR that gets rectified and pushed back into the rotor to get the output voltage to spec. It defs looks like the AVR is at fault/suspect here, juice the brushes with about 12VDC nominal and check your output terminal voltages, if they are LOWER than rated, you are fairly safe to continue. Then check any additional inputs into the AVR, there are usually at least one, sometimes two or even three pairs of wires coming back to it. If there are no voltages coming in to the AVR, shut down the unit and disconnect the AVR completely and try again. Still no voltages, then you might have lost or burnt one of the windings. If there are voltages present, above 20V nominally that is, then there is pretty much a certainty that the AVR itself is fried, a common occurrence....

In my limited experience with these creatures, the voltages to/from the AVR/Connectors are
(a) a "driver" output from the windings going into the AVR that gets regulated and fed back to the brushes to maintain output voltage
(b) a "sensing" voltage that is of fairly low current to power the AVR and used to "sense" the output of the main terminals for a control of the output voltage
(c) The regulated output from the AVR which goes to the brushes derived largely from (a)

Note: some AVR's have 2, 4 or 6 wires input as well as the 2 wires out to the brushes...

A brief way I understand them:
2 wire input AVR - a+b above are combined, still has c
4 wire input AVR - as above (most common around my neck of the woods)
6 wire input AVR - as above but sensing and supply are split, still has c - ie 2 sensing wires, 2 supply wires to power AVR, 2 "power wires" to be rectified, regulated and fed back to the brushes via (c)

This is all excluding the 2 or 4 or 6 "output" wires that go to the outside world to run your electrical doo-dahs....

A pertinent question though... with the AVR disconnected, the output wires disconnected and the unit not spinning ie just with the genhead electrically isolated from the rest of the world, have you checked for continuity of the windings and also that none of the windings are shorted to ground? (all winding resistances should be fairly low, in the region of less than 1000 ohms and all windings should have a resistance of greater than 100 000 ohms when measured between coil and chassis.)

If not - time for a re-wind!

Hope this helps

Cheers
Ed

Hi Ed,
Thank you for the explanation! I tried your suggestion and connected the brushes to a small 4 am battery charger. The voltage rose to 150 volts and stayed there. Is this about right? I only ran it for 30 seconds but thats huge progress for me! I assume your diagnoses of the AVR is correct. The AVR I ordered has arrived it's got the wrong plug and is 2-3 KV on the box so I assume it's useless? I wouldn't know which wire went where if I cut the plug off as the colours are different. I will have to order another one, Grrr
Thanks again
Paul
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