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OT/ flashing a generator

Discussion in 'Off Topic Threads' started by Haskins Bill, May 10, 2009.

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  1. Haskins Bill

    Haskins Bill TS Member

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    About a week ago there was question about flashing/exciting a generator to get it to put out electricity. Well I dug out my manual and here goes. The laminations of the rotor are designed to hold somoe residual magnetism. This is put into the unit during manufacture by applying and external source of DC voltage of proper polarity to the rotor. This is called flashing the field. Sometimes a generator will lose its residual magnetism due to vibrations during shipping or just travel. To flash the field using a lawn tractor battery of 6, 9, or 12 volt.: With the generator running touch a lead connected to the positive battery terminal to the positive brush terminal, and a lead from the negative battery terminal to the negative brush terminal. The DC voltage fed through the rotor windings should restore magnetism. Some manufacturers use permanet magnets to insure residual magnetism. Sometime even these types of units require flashing. A flasher can also be made using two D cell batteries and some 14 AWG wire and a 5 amp magnetic circuit breaker and a 120 volt two prong plug. Connect the batteries to feed negative side to one prong of the plug and the positive through the circuit breaker and then to the other prong of the plug. You can also make this up using a 9 volt transitor battery and the two prong plug and either the circuit breaker or a Buss type 5 amp fuse and holder. The circuit breaker/fuse is so you do not ruin the DC batteries and or short out the unit. With the flasher assembled and the generator running, plug the flasher into one of the 120 volt outlets. As soon as that DC votage hits the rotor the unit will put out AC if that indeed is the problem. Of course I would guess that you had already checked out the brushes for excessive wear. I would think that every one that uses a portable generator would have one of these made up ahead of time. Especially those that have generators in their RV's as the vibration of a trip might just cause the generator to not put out. During my generator class several years ago the instructor said not to pass up on generator at a yard sale, for a cheap price, that does not put out if the motor runs good. Many times all it takes is to 'flash' the unit and you will be good to go. I hope this helps. Bill
     
  2. Quack Shot

    Quack Shot Active Member

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    We called it "polarization". Be sure it's a generator and not an alternator that puts out AC current and is rectified to produce DC. If you attempt to polarize an Alternator, you could do some damage. During the polarization process, you need to connect to the proper side of the voltage regulator. There's a even a few videos on you tube showing how it's done. Otherwise, check for the manufacturer's website or try Google for more info.

    Where I come from, "flashing" can get you arrested if done improperly.
     
  3. Brian in Oregon

    Brian in Oregon Well-Known Member

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    Deplorable Bitter Clinger in Liberal La La Land
    I haven't had to do this since the days of my first vehicle, a 1952 IHC pickup. Brings back memories.
     
  4. creteham

    creteham Member

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    I think what we're talking about here is an ac portable power plant. I've had to do the "flashing" thing a few times on a couple of 'em that have sat a long time. I think you guys are thinking of "polarizing" an automotive generator or voltage regulator from "the good ol' days.

    Terry
     
  5. atashooter

    atashooter Member

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    Hook Red cable to left Nipple... Stroke Right nipple gently with wet Black cable. Doesn't do much for your generator, but it makes life exciting...
     
  6. ExFedex

    ExFedex Active Member

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    Jumper B/batt terminal off voltage regulator to A/field terminal briefly on old style generator with engine running. Watch voltmeter. Have fire extinguisher nearby. That was a long time ago, before alternators.
     
  7. Haskins Bill

    Haskins Bill TS Member

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    My post was in response to a post about a week ago and yes it refers to portable generator sets you would use in your RV or at your home during a power outage. The references about polarizing a generator on a vehicle brought back memories to me. My first car was a 1948 Plymouth! I got my info straight from the manual we used in a Generator class I took a few years ago. I think I will wait awhile before trying the battery cable to nipple trick. OUCH!!!
     
  8. Hauxfan

    Hauxfan Well-Known Member

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    And here I thought you were talking about these kinds of flashers.......lol

    [​IMG]

    I guess I got that wrong........lol

    Hauxfan!
     
  9. Tron

    Tron Supporting Vendor Supporting Vendor

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    Hi everyone! I'm back in town and I think that this thread may be in response to one that I posted a week and a half ago or so. Anyway, my generator is a Troy built and had nothing in the owners manual mentioning "flashing" nor did their ever_so_helpful robotic HOTLINE (all the HOTLINE did was make me even more pissed off....but that's a whole other story. Just try using it. It works with Phonetics and has A LOT to be desired). I had to figure this "flashing" thing out myself......just one of those things I guess.
     
  10. Quack Shot

    Quack Shot Active Member

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    I misread the first post, but Yes it's almost the same thing with an "AC" power "generator". The term Generator is often confusing for us old timers. If it does not have permanent magnets, then it may eventually need to be "flashed". It doesn't take much to get it going. You could be better off with the lead acid type battery like the lawn tractor or motorcycle type. The C Cell, D Cell, or 9V battery hook up would probably be better served with a 1 Amp breaker or fuse. I'd be careful with any of the units with an electronic regulator, which probably includes almost all of the units manufactured in this Century. The electronics can be damaged if done improperly. Some Marine and RV units may automatically do this if they are also connected to 12 or 24 Volt batteries or Vehicle power. Automotive Alternators have a Field circuit that is connected to a 12V source once the ignition is turned on. On many of these power generators, I believe that the field current is provided by rectified AC supplied by the unit. A bad fuse or rectifier could possibly have the same effect.

    I would not run the engine while doing the flashing. I'd try just cranking the engine over with the spark plug disconnected, provided it's a gasoline engine. Once it's been cranked over a few times, it should have enough residual magnetism to get it working again. I would also not hold onto any wires while doing this trick. On some of the larger marine units I worked with years ago, a serious spark can jump the gap when disconnecting the battery. Using the 120 volt plug, you'd probably be "flashing" the armature and not the rotor, but same difference as long as there is a magnetic field as a result. It would depend upon the design of the unit.

    Now for the odd stuff. The condition can be caused by the loss of "Excitation" in the Exciter Field. Those pumpkin pictures might not help unless the Exciter is really twisted.
     
  11. Haskins Bill

    Haskins Bill TS Member

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    Well I guess the instructor in the generator class was full of s##t then. He showed us the 9 volt batter set up and did it on a 'generator' that was running. He said to use the 5 amp fuse and the book shows a 5 amp circuit breaker. I guess Homelite which has been around since the 20's is full of s##t also. The post originaly was about home use type of generators. Many times a generator will lose its residual magnetism just sitting around unused or lose it from being transported and the vibrations affect it. I wrote my May 10 post using the manual from the class. I did not make it up. Just trying to pass on some helpful info and certain people want to make it more than what it is. Also I guess some fools would try making up the flasher using bare wires. Well if the got knocked on their keister then they deserve it. Better to have the 'flasher' made up ahead of time so that when you need that generator for real you will be able to use it!! Bill
     
  12. Tron

    Tron Supporting Vendor Supporting Vendor

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    I don't see how you could do this without the engine running.
     
  13. Quack Shot

    Quack Shot Active Member

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    Bill

    Never said anyone was full of crap on this thread and never said you were wrong to post it. Somehow you got your shorts in a wringer. You provided some useful information for an obscure problem. HOWEVER....If Homelite says to do it, will it work on every other unit out there? Is it SAFE on every other unit out there? I simply made some recommendations based on careful thought and experience. I do have a little experience in Electronic and Electrical Systems, so I thought that it would be relevant to comment. If you'd like to make the claim that Homelite has the only answer, then so be it. I offered a broader perspective. Take it or leave it, but I won't retract any of it unless you can find some clear and credible facts to the contrary. I'm usually willing to learn something new or re-learn something old. No disrespect intended.

    What I did say was that you can try it without the engine running. All it needs to do is crank over with sufficient voltage applied to the rotor and you should have enough residual magnetism to make it work. If you are lucky enough to have a procedure recommended by the manufacturer, then by all means use it. If not, be careful. I don't have much trouble with applying a DC voltage to the rotor, but plugging a 9V battery into a 120 Volt outlet with the generator running might not be a good idea. If it starts working, you should hope the fuse blows before the battery does. I'd rather incorporate a current limiting circuit, but a simple fuse can do. The 120V outlets are not usually connected to the rotor, but to the stator or armature, if the design specifies it that way. DC Voltage is usually applied to the rotor, but AC voltage is applied by the Stator to the outlets, although usually regulated. Tell you what, make up that 9V contraption and plug it into an outlet in your house. If the outlet is working, what might the result be? Would you seriously tell me that you'd consider holding on to the 9V battery and plug while you do this? All it takes is one errant event and you could have some serious short skidding material. Putting the voltage on to the Stator is sort of backwards, but it should still result in a magnetic field being created. I would still try it first without running the engine, if at all possible. Just cranking should be enough in most cases. The point about some units having an electronic regulator is that they CAN be damaged by voltages or devices applied where they shouldn't be.

    The caution about not holding on to wires, also applies to some that are generally considered to be "insulated". When the voltage is disconnected from the rotor or stator, the magnetic field collapses and generates a voltage when it does. It's the same principle that a vehicles ignition coil works with. The field builds slowly, but collapses very rapidly and can generate quite a high voltage through the windings. Enough sometimes to defeat some flimsy insulation, jump a gap, or create an arc. If you get hit by it, it could hurt a little. Not trying to be a smart ass, but I've been there.

    Tron,

    Think "electro-magnet". Think Windings and Ferrous core. The rotor does NOT have to be moving to create magnetism. Apply sufficient power and you have a magnet. Just turn it over to make sure it's fully energized by applying sufficient power through the collector assembly (brushes and slip rings) to the rotor. That way all of the rotor's field poles will be restored and not just the one that is connected at the time. There should be enough residual magnetism created to restore the "generator" to an operable condition. Designs can vary, but you should get the idea. I'd guess the reason it's not in the TroyBuilt manual or available from support is liability and the fact they want to sell you a new one or have you get it "serviced" so the dealer can make a few bucks.
     
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