"flashing" generator

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Old 02-18-06, 07:45 AM
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"flashing" generator

I need help on 'flashing' an AC generator. I have a Troy-Built 3550 watt AC generator that I was told by a repairman that it probaly needs to be 'flashed'. (He has done this to it once before). To save a trip to the repair shop, (time and cost), could someone tell me how I could go about flashing the unit? Yes, I do have a pretty fair knowledge of electrical circuits but this I'm not quite sure of. I do remember from the days of the old automobile generators that they too had to be flashed before they were run. Thanks for any advice,,,,,, Bill H
 
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Old 02-18-06, 07:51 AM
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I have no idea what is meant by this term in this situation. When you find out what he means, please let us know.

Before taking your generator to be repaired, I would discuss the potential cost of the repair with the shop. A generator that small may not be worth repairing, especially if it is older.
 
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Old 02-18-06, 08:26 AM
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I don't know the procedure but I can tell you what he wants to do. The residual magnetism in the field that gets the generator generating is too weak. He wants to apply a voltage to the coils in the generator to put some magnetism into them. I believe you would need a DC voltage(maybe not) but I could not tell you where or how to apply it.

Try googling "generator field flashing" and a bunch of links will come up.
 
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Old 02-18-06, 08:41 AM
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Originally Posted by pear4710
How I could go about flashing the unit?
You need to read the owner's manual. It could be as simple as feeding electric power into the alternator as if it is a starting motor but with the fuel shut off (but the crankcase filled with oil!). DC voltage is better as it will not cause rotation.

Flashing recharges the small permanent magnets that prime the alternator field coil.
You should use the alternator at least twice per year if it is old.
 
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Old 02-18-06, 09:38 AM
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Flashing a home backup power generator...

Originally Posted by pear4710
I need help on 'flashing' an AC generator. I have a Troy-Built 3550 watt AC generator that I was told by a repairman that it probaly needs to be 'flashed'. (He has done this to it once before). To save a trip to the repair shop, (time and cost), could someone tell me how I could go about flashing the unit? Yes, I do have a pretty fair knowledge of electrical circuits but this I'm not quite sure of. I do remember from the days of the old automobile generators that they too had to be flashed before they were run. Thanks for any advice,,,,,, Bill H
I did this last night on a Honda EX4500 gas generator. Single cylinder, 11 hp, fairly conventional generator design. The procedure came from the service manager of a here-unnamed generator shop. You'll need minimal tools/accessories, and a charged 12 volt battery. Obviously you proceed at your own risk, and the exact procedure for your unit may differ. Do this outside if possible, and remember that you'll be creating a spark, which does not go well with gasoline vapor.

----------------------------------------------------------------------

Do this with engine turned OFF! Explosion can occur if done while engine running!

1. Remove spark plug wire so that engine can't start.

2. Locate the "generator" end of your engine, with all the electrical components and wiring. My generator is enclosed, and required end panel removal.

3. Locate the brush set. The engine rotates on a center axle (crank), and has two brass "slip rings" which have been pressed (like collars) onto that axle. The spring-loaded brushes will be mounted (somehow!) on the engine frame near the center, and will contact those slip rings.

4. Find the two wires that attach to the two terminals on the brush assembly. Note which goes where, then disconnect them.

5. DETERMINE WHICH BRUSH IS POSITIVE, AND WHICH IS NEGATIVE! Call a dealer if necessary! On mine, the inner brush was positive with a red wire, and the outer brush was negative with a white wire.

7. Securely connect a spare, color-coded wire to each brush terminal. I used small Radio Shack-type jumpers with insulated alligator clips connected to longer wires.

8. Attach the wire connected to the positive brush terminal to the positive terminal of the 12v. battery.

9. Touch the wire connected to the negative brush terminal to the negative terminal of the 12v battery. You want this to be a firm but momentary contact, with a quick but noticeable spark to confirm that the circuit has been completed. More contact time is not better!

10. Remove jumper wires from battery and brushes.

11. Remove the brushes and inspect them for defects or loose connections. My brushes came in a modular cluster held in place by a locator pin and one screw.

12. Clean the slip rings while the brushes are removed. I used alcohol, a Scotch-brite pad, and a shop towel. You should find a bolt head on the end of the center axle; I used a ratchet to rock the engine back and forth between (not through) compression strokes to access the entire surface of the two slip rings. I state "between (not through) compression strokes" because you don't want your ratchet to act as a pull-starter and start the engine if you didn't disconnect the spark plug wire! Scrub the the slip rings until they're bright and clean, and dry them well with the shop towel. Clean/dry the curved contact surfaces of the brushes as well.

13. Reinstall brushes and brush wiring per your initial diagram.

14. Reinstall spark plug wire.

15. Restart generator.

If still no output, the service manager identified the voltage regulator and diode pack as the two next likely culprits. The diode pack should show continuity in one direction (only) with a meter; the voltage regulator probably would require a trip to the shop with your generator for troubleshooting.

Good luck! and repost your results...
 

Last edited by ksnh; 02-18-06 at 10:13 AM.
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Old 02-18-06, 12:05 PM
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Originally Posted by ksnh
5. DETERMINE WHICH BRUSH IS POSITIVE, AND WHICH IS NEGATIVE! Call a dealer if necessary! On mine, the inner brush was positive with a red wire, and the outer brush was negative with a white wire.
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100% YES.
--------------------------


The original term was Polarizing a Generator. In you case I would say Polarizing the rotor.
They keep changing the terms so its harder to get old information.

Search the web for Polarizing a Generator.
--------------------------------------------------------------
I would be cautious about using a 12 volt car battery without knowing what the voltage and current that rotor runs at.

A 12 volt car battery can supply over 100 amps, if the required rotor voltage is lower then 12 volts you may burn it up without using a resistor to limit the current thru the rotor.

Diodes have polarity markings that should help you determine the plus and minus going to the rotor.
I would disconnect the wires to the brushes to avoid back feeding power back into the diode bridge and whatever.
only feed power into the rotor if you can.

Let me know if you find a good link, its something that I have not had to do to my 20 year old generator that I only use every 3 years.

Just one link on Polarizing a Generator for cars.
http://www.nls.net/mp/volks/htm/gen.htm
 
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Old 02-21-06, 11:43 AM
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Great Help!!!

My little 'issue' with the generator turned out to be successful thanks to the help given. I commend all who kindly offered advice. All worked out well. Thank you one and all. pear4710
 
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Old 02-21-06, 07:01 PM
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Very valuable info in these posts, How ever my gen of 15 years never needed this,tune ups,oil, etc.
Just curios why some do. always like to know the abstract. Thanx.
 
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Old 02-21-06, 07:07 PM
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If the generator is used often enough, it shouldn't ever be a problem.
 
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