John T or Gerald J Simple Question...

Since I am just a simple mind (electrically). Have read all the posts and archives reguarding "polarizing" a generator. I have learned all about "how" to do it. Three questions arise. First...why does it need done ? Second...how do you know if it needs done ? Third....in all the articles , it doesn't say whether the engine is running or not. Probably all pretty much a no-brainer in your world but like I told you , my brain just seems to have never made room for electrical theory. I'm sure others will thank you along with me for your answers. "B".

A generator gets itself "started" due to a weak magnetic field that must exist in the field coils of the generator.

That field must be the correct polarity for the generator to work.

To polarize, you just send power to those fields for a second to establish that field. It can be done without the engine running.

All you are doing is, by hitting the fields with power, making them work as an electromagnet while that power is on, and when "off", they retain some of that magetism so the generator will work the next time, without any power added.

Alternators differ because they work by always feeding power at first to make the "excite" magnets work. They do not rely on residual magnetism like a generator does.

Good questions actually, it shows someone actually cares and thinks about WHY..

Three questions arise. First...why does it need done ?

It should be done so when the genny starts spinning and pumping out current IT DOES SO IN THE SAME/CORRECT POLARITY TO MATCH THE POLARITY OF THE BATTERY.. Think about it, if you attach a battery charger you want it at the correct polarity right??? If its at the opposite polarity its possible the Voltage Regulator may be damaged also!!!! When you Polarize you pass current through the gennys Field windings at the correct direction/polarity (matching battery) it imparts a degree of residual magnetism in the soft iron field poles with the correct North/South magnetic polarity so when the armature starts turning the correct corresponding Electrical +/- Polarity is generated YAYYYYYYYYYYY

Second...how do you know if it needs done ?

It should be done if the genny has been worked on,,,,,,, Or off the tractor a longgggggggggggggg period of time,,,,,,, or the battery has been reversed OR YOURE JUST NOT SURE as it never hurts

Third....in all the articles , it doesn"t say whether the engine is running or not.

NOT RUNNING AND BEFOREEEEEEEEEE YOU START THE TRACTOR to avoid potential VR and/or battery harm.

Hope this answers your questions and in my opinion my friend Gerald knows moreeeeeeeee about DC motors and Gennys then I do, Im long retired as an EE he still practices

John T

jd posted:

"It CAN be done without the engine running."

It would be better to say it MUST be done BEFORE the initial startup of the engine with the new/repaired generator.

If you wait and start the engine FIRST, you run the risk of the generator beginning to charge with the incorrect polarity which will lead to stuck cutout contacts and probably a certain amount of smoke leaking out of the generator and cutout/VR at shutdown.

So, for best results polarize BEFORE starting the engine.

I replied that way because he specifically asked about it. Technically, it could also be done with the engine running. Why anybody would want to is another issue.

The guy that asked the incipient question also asked for simplicity. Thus I atttemped to be brief and to the point.

But, he only asked two specific people to reply, so in that regard - I am in violation. Too bad.

Thanks to all who responded. Now I know "the rest of the story". Questions cost me nothing. Mistakes are expensive. If one acts without first asking or getting educated then that is either ignorance or stupidity. Again , I am greatfull to all who volunteer their wisdom on this forum. If we all had to learn everything from our mistakes , we would be dead before we were smart. Thanks again. Randy.

I can't add anything.

Gerald J.

When polarizing, I like to test run the generator as a DC motor at the same time. Makes a good test of the gen's status.
Loose off the drive belt. Push the cutout contacts together in the regulator with a wooden or plastic popcycle stick. Generator should motor. Using another stick while still motoring, open the field contacts. The generator should motor faster.

jd,

My addition to your reply is a valid comment, intended to be helpful, and MAY help someone NOT damage their cutout/VR and/or generator.

So does it make you feel good to make be a puncture wound and make the "I am in violation. Too bad." remark back at me?

You just CAN'T help yourself, can you?

Who is now trying to be a "PR*CK?" as you say?

My comment about me being in "violation" was intended to be about only me, and had absolutely nothing to do with you or your comments.

I felt a little out-of-place commenting on the original question since the poster requested a simple response from two specific people. I am not one of them, but I did try to keep in simple. My "too bad" comment, to translate into diffferent words, simply means "my input is free and if unwanted, too bad and no harm done."

Why that gets you upset, I can only imagine.

Do you really have an interest in old tractors, or just picking verbal fights behind a keyboard?

I've been posting on these forums for a long time and have never gotten rude or out-of-hand with anybody, unless they got so with me, first - as you seem to be attempting here.

I try to be aware of the limitations of expressing one's ideas via a keyboard with no vis-a-vis contact. Without context, things sometimes come across differently then intended. So, I try to interpret people's comments by context over time if I recognize them. And, I hope other's do the same for me. And you? Are you just looking to start trouble? It's crap like this that often ruins good forums.

Don't make me come out there!! Bob , I appreciate your clarification post as i can see where one might read JD,s the wrong way. While one or two misplaced words can make a big difference , I really think that the only error Jd may have made was "overthinking" the original question. Tyr to get along. Hopefully we ALL learned something. I know I did. Thanks to all.

jd.

You NEVER expound on anyone else's posts, only make you own. You know more than ANYONE else.

You are obviously the definitive alpha male and a puncture wound. so be it, puncture wound!

Enough said.

Very astute Bob. I'm humbled by your droll wit and expertise. Better keep taking your anti-depressants.

I'm still not sure what the heck your real problem is, but I guess anybody can post whatever they want on a free forum.