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Go Back   SailNet Community > On Board > Gear & Maintenance > Engines > Diesel
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Diesel This is a new forum dedicated to diesel engines and their applicable accessories.


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  #1  
Old 10-08-2013
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Depolarized VP2030 alternator?

Hello!
I would very much appreciate advices about this problem
My VP2030 starts immediately and runs softly.
Suddenly the non charging alarm sounds.
Tester measurements on the alternator output indicate no charging.
The alternator was dismantled showing that all components were OK.
The mechanic said that "he polarized the alternator" and subsequent bench measurements showed that the alternator was performing very well, charging without problems.
Anybody has an idea about what could have happened in the engine for depolarizing the alternator?
Where to look in order to avoid another depolarization?

Thanks in advance!
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Old 10-08-2013
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Re: Depolarized VP2030 alternator?

Depolarized? Look at the regulator. A shakey solder joint or an overheating zener diode.
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Old 10-08-2013
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Re: Depolarized VP2030 alternator?

regulator issues
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Re: Depolarized VP2030 alternator?

Must be a translation problem. One doesn't "polarize" an alternator. An alternator has no inherent polarity until the regulator gets added into the wiring, and then the polarity is fixed and permanent, based on the construction of the regulator. There's no way a mechanic can change that, or "re-polarize" or "un-polarize" it.

I'm guessing a VP2030 is a Volvo Penta engine, but that doesn't tell us what kind of alternator they bolted onto it, or what kind of regulator is being used.
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Old 10-09-2013
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Re: Depolarized VP2030 alternator?

I believe its a standard, very ordinary, cheaply repairable, Bosch alternator (need to check this when down at the boat next) - the type with the regulator bolted on the back of the brush holder.

FWIW, if I was having charging issues, I'd pull the alternator off (2 bolts) and take it to a local Auto Electrician... and if my mechanic started talking about "polarisation", I'd be finding a new mechanic.
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Last edited by Classic30; 10-09-2013 at 06:53 PM.
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Re: Depolarized VP2030 alternator?

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Originally Posted by hellosailor View Post
Must be a translation problem. One doesn't "polarize" an alternator. An alternator has no inherent polarity until the regulator gets added into the wiring, and then the polarity is fixed and permanent, based on the construction of the regulator. There's no way a mechanic can change that, or "re-polarize" or "un-polarize" it.

I'm guessing a VP2030 is a Volvo Penta engine, but that doesn't tell us what kind of alternator they bolted onto it, or what kind of regulator is being used.
my initial thought was the same as yours. But it seems to me years ago I ran into a situation in which the soft iron core became magnetized by high voltage spike so that it was canceling part of the electromagnetic force resulting in an alternator that seemed fine but had low output. the fix was to demagnetize the cores. maybe that's what he meant by polarizing/?
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Old 10-15-2013
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Re: Depolarized VP2030 alternator?

Finally I understood what the electrician meant with "polarizing".
My alternator has an additional field which is initially excited in order to start its electricity production.
He connected tentatively this field (D) to the +B (Batery) through a small 6 Watt 12V bulb.
Once the alternator starts producing energy the volt difference between D and +B dissapears and no more current flows through the bulb.
We suspect a wiring problem cancelling the initial necesary excitation current.

Now the alternator works fine!
I thank the useful advices!.
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Re: Depolarized VP2030 alternator?

It is normal for an alternator to require "excitation" current. As opposed to a generator, which usually uses permanent magnets instead.
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Re: Depolarized VP2030 alternator?

Quote:
Originally Posted by Ulfilas View Post
Finally I understood what the electrician meant with "polarizing".
My alternator has an additional field which is initially excited in order to start its electricity production.
He connected tentatively this field (D) to the +B (Batery) through a small 6 Watt 12V bulb.
Once the alternator starts producing energy the volt difference between D and +B dissapears and no more current flows through the bulb.
We suspect a wiring problem cancelling the initial necesary excitation current.

Now the alternator works fine!
I thank the useful advices!.
the excitation voltage is supplied by the battery. A generator will charge with a dead battery but an alternator needs a good battery to charge. So your battery was completely dead? If it wasnt then the battery lead from the bat to the alt has a cold solder joint or some other intermittant open in the circuit.
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Old 10-17-2013
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Re: Depolarized VP2030 alternator?

Generators/Alternators confuse me so I did some research. This was an interesting thread:

Boat Buzz ? View topic - re-polarizing a generator
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