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Discussion Starter #1 (Edited)
The alternator may well be the hottest topic on this forum and often a catastrofic hot item inside the engine.


Having a fairly good insight in physics, electrical machines, electronics and general Do It Yourself work, I have now written this Alternator Tutorial - Motorcycle DIY Article with the following headliners:
  • Principle of Operation
  • Fundamental Problems for Permanent Magnet Alternators
  • Measurements, Symptoms and Failures
It is my hope that this article will help people to understand what is going on and why alternators fail.

It is also my hope that this thread will be used actively by fellow members who want to contribute with review, comments, pictures (which I still need) and with additional test results and documentation.

Some of this has already happend in theese ealier threads:
- Charging System Question!!!
- Charging Problems!! HELP!!!

Later today I will make a link back from the article to this thread, so the feed-back loop is closed.

Cheers ... Fred :)
 

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Hello,

I've read your article about the alternation and I would like to ask you if you know the stator AC output frequency.
I've bought a 2-phases FXD-125 R/R for my motorbike (CRF 450) and I noticed that the DC voltage output drops when the motor's RPM go up.
At idle, I can measure 12VDC at the R/R output.
If I rev up my bike, then the voltage output drops to 5-6VDC and this is very strange for me.
For this reason, I would like to test on my workbench the R/R by giving it an AC input.
I was thinking to use a 220VAC-24VAC transformer as input for the R/R in order to check if the voltage drops again (I'm in Italy, 220VAC is at 50Hz).
I already checked the AC voltage which comes out of my stator wires and everything is OK since it increases when I rev up the motor so the stator is surely OK.

Thank you for your suggestions!
 

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Discussion Starter #4
Hi Marcusbarnet,
Sorry didnt see your post untill today, as I'm not so frequent in here.

I never speculated about the exact frequency comming out from the alternator, bu it must be a few cycles per cranck shaft rotation. Probably something like number of poles devided by six but I'm not sure.

Your alternator may very well put out enough voltage as you measurement results says, but if there is a short to ground from it, the RR will not give correct output. Did you check continuity to ground?
 
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