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Thread: generators

  1. #1
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    Default generators

    ok we have all seen the generators/welders on job sites that run off of propane and are towed with a trailor. my question is how do you polarize a generator like that once it has set of a number of years?

  2. #2
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    Default Re: generators

    Not getting your question.
    "" an ounce of perception -- a pound of obscure "
    - Rush

  3. #3
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    Default Re: generators

    I though they were all alternators. Alternators don't need to be polarized. If it is a generator, first determine if it is negative or positive grounded. The opposite pole wire would be wired to the relay and through it to the battery. In a negatively ground system you would momentaerily jumper from the positive post of the battery to the wire going from the relay to the generator. Posative grounded system jumper from negative post. This should always be done whenever the battery or the gerantor has been disconnected
    Jack
    Be sure you live your life, because you are a long time dead.-Scottish Proverb

  4. #4
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    Default Re: generators

    Never had a need for polarizing a portable welding rig --- maybe I'm missing something.
    "" an ounce of perception -- a pound of obscure "
    - Rush

  5. #5
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    Default Re: generators

    Canuk, if I understand things correctly, some generators don't have permanent magnets, but rather depend on residual magnetism in the laminations to "kick start" the generation process. When left to sit long periods of time, these generators lose their residual magnetism and thus cannot generate electricity. This requires remagnetizing (polarizing) the laminations before using the generator again. The process is roughly as Jack describes, but I've never done it so don't ask me for more details! I have a friend who had a welder/generator that had the same problem and he used a process something like that to get it working again.
    The "Senior Member" designation under my name doesn't mean I know a lot, it just means I talk a lot.I've been a DIYer since I was 12 (thanks, Dad!). I have read several books on various home improvement topics. I do not have any current code books I can refer to. I was an apprentice plumber for two years.

  6. #6
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    Default Re: generators

    A generator can deliver current for either a positive or a negative ground system.
    A generator produces current by passing conductors (the armature windings) through a magnetic field. The magnetic field is produced by electromagnets that surround the armature. the polarity of the current is determined by the polarity of the pole shoes, or the direction of the magnetic flux or field, which is determined by the direction of current through the field windings.
    When you start your engine, the generator will start delivering current. Since the generator is still isolated from the electrical system by the voltage regulator or cutout relay at this point, it will start producing current based on the polarity of the pole shoes. As soon as it begins producing current, some of that current will be directed to the field windings to strengthen the magnetic flux.
    If the generator polarity is reversed, the generator will build up voltage and close the cutout relay points. This put the generator in series with the battery, and their voltages are added together. This high voltage across the points (about twice the battery voltage) can cause high current and enough heat to weld the points together.
    The instant the points close, the voltage is about the same on both sides of the relay coil, so very little current flows, and spring tension reopens the points. But, generator voltage will again close the points, and the cycle will repeat at a rapid rate. Heat and arcing will finally weld the points together.
    When the points weld, the battery and generator are connected in series at all times. The low resistance of the generator allows the battery to continue to discharge through the generator. The high current can create enough heat to burn the armature. And it doen’t take long to get a big cloud of black smoke.

    Jack
    Be sure you live your life, because you are a long time dead.-Scottish Proverb

  7. #7
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    Default Re: generators

    If a generator sets for a long time unused, the polarity established by the windings can fade and the residual polarity of the shoes can become predominate and reverse polarity. That is why they need to be repoloraized if they have been in storage for a long period of time.

    Jack
    Be sure you live your life, because you are a long time dead.-Scottish Proverb

  8. #8
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    Default Re: generators

    Could i jump terminals in the voltage regulator from the battery to the field terminal?

  9. #9
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    Default Re: generators

    Quote Originally Posted by Edgeking View Post
    Could i jump terminals in the voltage regulator from the battery to the field terminal?
    You jumper from the ungrounded battery terminal to the ungrounded field lead from the generator going to the voltage regulator.
    Jack
    Be sure you live your life, because you are a long time dead.-Scottish Proverb

  10. #10
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    Default Re: generators

    Thanks i am going to give it a try tonight most likely.

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