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Old 07-06-2011, 02:48 PM   #1
trainer
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Default remagnetizing a generator

I have a 3,000w generator that isnt working after spending a year in storage.

The engine runs great (I used Sta-bil and changed the oil before storing it)

It's a chinese made honda clone thats about five years old, non inverter type.

I've checked the circuitryand everything seems ok. I'm getting about 6 volts across both sets of windings.

Theres a schematic sticker included on the genny.

Since everything seems to check out, I think the field may have lost its magnetism.
Should I look for anything else before I try to remagnetize it?

Does anyone have any tips for this procedure?
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Old 07-06-2011, 07:26 PM   #2
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Default Re: remagnetizing a generator

Different generators need different techniques, so there is no (IMHO) generic answer. You are talking about 'flashing' the armature, I'd do a web search with the words 'flash generator' and perhaps the model/make of your set.

Can you scan and post the schematic?
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Old 07-06-2011, 09:18 PM   #3
Charles (in GA)
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Default Re: remagnetizing a generator

Picked this up off of Yesterdays Tractor Magazine Tool forum......... never tried it, but others on the forum said they had and that it did work.

Charles

Field Flashing of Portable Generators

This tip comes from the Briggs & Stratton Customer Education Department. As an alternative to flashing a rotor winding with a battery applied to the brushes, an electric drill may be used. Follow these steps to flash the generator:
• Plug the electric drill into the generator receptacle. (Cordless drills do not work)

• If the drill is reversible, move the direction switch to the forward position.

• Start the generator

• While depressing the trigger on the drill, spin the drill chuck in reverse direction. This will excite the field and the generator will now produce electricity. If spinning the chuck one direction does not work, try spinning the chuck in the other direction as you may have the reverse switch positioned backwards.
Use caution not to get your hand or other materials caught in the chuck. As soon as the field is excited, the generator will produce power and the drill will turn on.
The reason this works is because the electric motor in the drill will act as a small generator when spun backwards. The magnets in the drill's motor induce a voltage into the motor windings, which is fed back through the trigger, cord and into the generators receptacle. From there it goes into the power winding of the stator. The voltage going through the power winding creates a magnetic field, which is intensified due to the iron core of the stator laminations. The rotor intersects this magnetic field as it is spun past the power winding, thus inducing a voltage in the rotor winding. Once current flow is present in the rotor winding the rotor has been flashed.
If flashing the field does not make the generator work, you may have additional problems, besides a lack of magnetism in the rotor. Further testing will be needed. Hopefully, this will give a simple way to field flash your generator if needed -
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Old 07-06-2011, 09:44 PM   #4
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Default Re: remagnetizing a generator

well, I learned something tonight! Thanks Charles
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Old 07-06-2011, 09:54 PM   #5
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Default Re: remagnetizing a generator

Thanks for the reply.
I dug a bit deeper and found that this generator has a separate winding with a rectifier to power a dc circuit. The DC from that circuit is also used to excite the field. So technically it's really an alternator, not a generator.
My ohm meter showed the rectifier to be defective.
Disconnected that winding and hooked a 12vdc battery to the field, started it up, and voila! 130 volts ac came out.

A new rectifier shouldnt be too hard to find or make.

Last edited by trainer; 07-07-2011 at 08:31 AM.
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Old 07-06-2011, 09:59 PM   #6
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Default Re: remagnetizing a generator

Quote:
Originally Posted by Charles (in GA) View Post
Picked this up off of Yesterdays Tractor Magazine Tool forum......... never tried it, but others on the forum said they had and that it did work.

Charles

Field Flashing of Portable Generators

This tip comes from the Briggs & Stratton Customer Education Department. As an alternative to flashing a rotor winding with a battery applied to the brushes, an electric drill may be used. Follow these steps to flash the generator:
Plug the electric drill into the generator receptacle. (Cordless drills do not work)

If the drill is reversible, move the direction switch to the forward position.

Start the generator

While depressing the trigger on the drill, spin the drill chuck in reverse direction. This will excite the field and the generator will now produce electricity. If spinning the chuck one direction does not work, try spinning the chuck in the other direction as you may have the reverse switch positioned backwards.
Use caution not to get your hand or other materials caught in the chuck. As soon as the field is excited, the generator will produce power and the drill will turn on.
The reason this works is because the electric motor in the drill will act as a small generator when spun backwards. The magnets in the drill's motor induce a voltage into the motor windings, which is fed back through the trigger, cord and into the generators receptacle. From there it goes into the power winding of the stator. The voltage going through the power winding creates a magnetic field, which is intensified due to the iron core of the stator laminations. The rotor intersects this magnetic field as it is spun past the power winding, thus inducing a voltage in the rotor winding. Once current flow is present in the rotor winding the rotor has been flashed.
If flashing the field does not make the generator work, you may have additional problems, besides a lack of magnetism in the rotor. Further testing will be needed. Hopefully, this will give a simple way to field flash your generator if needed -
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Old 07-06-2011, 11:20 PM   #7
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Default Re: remagnetizing a generator

I have never heard the electric drill deal, but it makes perfect sense! We used to use a 9-volt battery stuck in the plug. Yeah, sound freaky, but you just quickly stuck it in there and pulled it right out. It didn't take much to get them going.

We used to actually have a special tool that was a "field flasher". It had a battery and a circuit breaker in it. You plugged it in and it would flip the breaker instantly. Unfortunately those things are uber rare.
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Old 07-07-2011, 06:47 AM   #8
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Default Re: remagnetizing a generator

Quote:
Originally Posted by Charles (in GA) View Post
• Plug the electric drill into the generator receptacle. (Cordless drills do not work)
Hahahahahaha!!!! Sorry...just couldn't help myself.
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Old 07-07-2011, 08:09 AM   #9
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Default Re: remagnetizing a generator

Quote:
Originally Posted by Charles (in GA) View Post
Picked this up off of Yesterdays Tractor Magazine Tool forum......... never tried it, but others on the forum said they had and that it did work.

Charles

Field Flashing of Portable Generators

This tip comes from the Briggs & Stratton Customer Education Department. As an alternative to ....
Wow!!
Great information... thanks for sharing!
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Old 07-07-2011, 08:15 AM   #10
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Default Re: remagnetizing a generator

Wow, you learn something new every day on this site. I had no idea this was even a problem. Well, next time I run into a generator that wont generate, I know what to do.

Tom
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Old 07-07-2011, 09:44 AM   #11
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Default Re: remagnetizing a generator

Quote:
Originally Posted by darkk View Post
Hahahahahaha!!!! Sorry...just couldn't help myself.
I laughed because the first thing I thought of too was "that won't work with a cordless drill", then reread "electric drill".

How many people still have plug in drills? My old hammer drill and 1/2" industrial drill rarely get used...
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Old 07-08-2011, 08:32 AM   #12
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Default Re: remagnetizing a generator

I dug out the defective part and looked it up on the importer's website. They want $14.95 plus $20 s& h. Add sales tax and it would be $40

It's a 35 amp, metal case bridge rectifier.

So I went looking and found the exact same part on Ebay for 96 plus 33 s&h.
It ships from Hong Kong and should take 1-2 weeks to get here.

Apparently the mark-up on parts is pretty hefty.

Last edited by trainer; 07-08-2011 at 08:36 AM.
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Old 07-08-2011, 12:05 PM   #13
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Default Re: remagnetizing a generator

Quote:
Originally Posted by carhunter View Post
How many people still have plug in drills? My old hammer drill and 1/2" industrial drill rarely get used...
I have five 120v AC drills, but no cordless ones. The batteries died on the cordless so I junked the drills. The AC ones just keep working.
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Old 07-08-2011, 06:59 PM   #14
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Default Re: remagnetizing a generator

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Originally Posted by carhunter View Post
How many people still have plug in drills? My old hammer drill and 1/2" industrial drill rarely get used...
I still have the JC Penny 3/8 variable speed electric drill that my wife bought for me on our first Christmas in 1971. It has a short body and will fit in spaces where the new cordless is too long or too big. It is a great reserve tool when the newer tools crap out or don't fit the job. It's almost as dependable as my wife!!
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Old 07-11-2011, 11:48 PM   #15
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Default Re: remagnetizing a generator

Quote:
Originally Posted by Displaced Hokie View Post
We used to actually have a special tool that was a "field flasher". It had a battery and a circuit breaker in it. You plugged it in and it would flip the breaker instantly. Unfortunately those things are uber rare.
Something like this?



http://hdrsellit4u.mybisi.com/produc...-field-flasher
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Old 11-26-2011, 04:59 PM   #16
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Default Re: remagnetizing a generator

Just wanted to thank those persons that posted using the electric drill to remagnetize a portable generator. It works without any problems.
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Old 11-26-2011, 07:42 PM   #17
Charles (in GA)
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Default Re: remagnetizing a generator

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Originally Posted by ChuckH View Post
Just wanted to thank those persons that posted using the electric drill to remagnetize a portable generator. It works without any problems.
Thanks for letting us know it works. I've never tried it, but the forum where I picked it up, one or two people said they have tried it and it worked.

By the way, welcome to Garage Journal, hope you stick around and enjoy the forums. Something here for nearly anyone interested in cars, trucks, motorcycles, or garages or shops or things mechanical.

Charles
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