3020 generator polarizing

~Those old generators are a marvelous thing of charging hardware.. If fact they’re so good they can & will charge either polarity or direction just by how the field shoe iron cores are initially polarized [a fancy word that means magnetized]..

~A generator works in a couple of different ways.. The first way is as a permanent magnet generator & that is: after initial installation or after starting before it puts out enough current to self power the internal field windings.. For that it depends on the residual magnetism in the field shoe irons [that is set by the polarization or magnetization process]…

~Then once it is spinning fast enough to produce enough of it’s own internal power [from those field shoe permanent magnets] to electrically power up the internal field windings, it then relies on electromagnet field strength & from then on the charging rate is controlled by the regulator, or headlight switch & generator’s 3rd brush position.. At that time it also makes enough power to charge the battery or power the lights..

~Basically when you polarize a generator ALL you are doing is setting the POLARITY DIRECTION it INITIALLY charges at.. Once a generator is polarized it always charges the same polarity [direction] unless it is re-polarized to something different.. That is what the service manual is getting at.. It wants you to re-polarize after ANY electrical work just to be sure you didn’t accidentally change the tractor polarity [like installing a battery backwards] or generator polarity [like touching a hot wire to the generator/armature circuit]..

~Should you ALWAYS re-polarize?, YES.. Do you ALWAYS HAVE TO re-polarize?, NO… It’s just a good insurance that you won’t burn up a regulator or cause other system damage.. The good part!! It only takes a few seconds to re-polarize..

JDClooney@aol.com

The Generators Field poles (1 on each side wired in series) consist of wire wound around an iron core. When you pass current through a coil of wire a magnetic field is produced and when theres iron or other magnetic material present, it becomes magnetized (creating an electromagnet)with a particular magnetic North/South Polarity dependant upon the direction of current flow. Also, even after the current is discontinued, a certain amount of residual magnetism remains in the iron (the field poles). Next, if you pass a coil of wire within or next to a magnetic field, a voltage is induced between the wires ends. Thats how the Generators rotating armature (which is a coil of wire) has voltage induced into it to charge the Battery. However, when the Generator just initially begins to spin, theres no battery voltage connected to it (cutout relay between Battery and Generators Armature output) is open which could cause current to flow through the Field windings and create a strong magnetic field. But that residual magnetism imparted into the field poles from Polariation is present so it can still begin to charge as theres still a coil of wire (armature) moving within a magnetic field (residual magnetism in the field poles iron), NOT the later stronger electromagnet created by current flowing through the Field windings wrapped around the iron poles.

When you polarize by attaching hot battery voltage to the Generators Armature post and having the other end of the Field grounded, you pass current through Generator and properly magnetize the poles in the CORRECT NORTH SOUTH polarity to match the direction of curent flow that passes through the Field windings once shes up n running. Youre in effect, matching up with the batterys wiring polarity, such as POS or NEG ground and why a Gen can still work in either Polarity.

When you install a new Generator and the battery is attached and you polarize, thats when everything (current and magnetic field orientations) is established and residual North/South magnetism is imparted (you Polarize the Generator not the Voltage Regulator) and when the tractor is shut down, the battery is no longer attached to the Generator (assuming cutout relay works) but that residual magnetism remains in the iron field poles. If the tractor were to set for a very very long period, that residual magnetism could weaken which is why one might re polarize when shes sat long or a different battery is installed.

Ive disconnected and re connected and changed batteries entirely and NOT repolarized and shes worked fine. If the cutout relay (stand alone or within a Voltage Regulator) is working and open, when the tractors off, the Gen isnt connected to the battery anyway. The VR's BAT terminal is where the hot battery voltage is attached but theres no curent flow in the Generators Armature or Field windings, its just sitting there disconnected from the battery, regardless if inside the VR (i.e. cutout relay is open) or the battery were disconnected at its post.

Therefore, to your second question, I dont think its necessary to re polarize the Generator if the battery were disconnected and re connected (AT SAME POLARITY OF COURSE), but on the other hand, it cant hurt anything either.

You mentioned you had a theory, what are your thoughts or opinions on the necessity of re polarizing if a battery were disconnected then re connected????? ???? Like I said, if she has sat a long period and the residual magnetism in the Field poles weakened, I can see re polarizing, but so long as YOU ARE NOT CHANGING/REVERSING BATTERY POLARITY, I think she will still work okay even if you dont. To be safe, I can see why VR manufacturers tell you to polarize the Generator but thats cuz one may be simultaneously installing a new previously unpolarized or reverse polarity Generator at the same time.

Great question, I cant wait to hear your and others theories n opinions about why one should re polarize each time a battery were disconnected, hopefully we can all learn and benefit from your question. All I can say for sure is Ive disconnected and re connected batteries and never re polarized and never had a problem. I do see how if shes sat long periods it may be necessary to re polarize however (residual magnetism weakens). Mabye I done bad and hurt something over the years????? ? lol.

Good Luck n God Bless ya Joe, cant wait to hear your and others thoughts, opinions n theories.

John T

Generally, polarization is needed after the generator has sat unused a LONG time, or been apart for repairs. What polarization does is restore the tiny amount of "residual magnetism" that lingers in the field pole pieces of the generator between times of operation.

This tiny bit af magnetism causes the generator to begin producing current upon startup. This first, tiny amount of current into the field coils further magnetizes the pole pieces, and the generator begins charging big time.