Been out of town so I'm a little late in weighing in on this one but being
an Electrical Engineer I had comment. The alternator puts out a 3 phase
sine wave, not a square wave. The 3 phase rectifier, made up of the 6
diodes, takes the negative half of the wave and makes it a postive wave.
Therefore, the waveform going into the battery and electrical system is made
up of 6 half sine waves at double the frequency of the alternator, i.e. if
the alternator is turning 6000 RPM, 100 revs per second or 100 HZ, the
frequency of the half sine waves is 200 HZ. Sine waves are very nice in
that there are no "sharp edges" to generate high frequency (thousands of
HZ) harmonics to cause electrical interference. The inductance (coil or
choke) of the alternator plus the inductance and capacitance of the battery
is enough to smooth these half sine waves out and make it into DC. I'm not
aware of any automotive system that used capacitors in the alternator
circuit for smoothing the sine waves or for noise suppression.
What is most likely the problem is the regulator. It switches current to
the rotor of the alternator through the slip rings and brushes to control
the charging. In that is switches (on and off) it does create sharp edges
which will generate electrical noise. I suspect the regulator "went South"
and that is the problem. I wonder if it is charging very well also. As
most of the alternator installions of the TR's are in place of the original
generators, the alternator, and therefore the regulator on the back of the
alternator, are only a couple of inches from the exhaust header of #1. I
suspect the heat from the header is taking out the regulator. It would be
well to duct a goodly supply of fresh air to alternators on TR motors. The
old generators didn't have any electronics to get cooked so it didn't matter
that they are right up by the exhaust header. The regulator, especially the
newer ones using integrated circuits, are going to be very susceptible to
heat. On some Mercedes cars I've seen where they have a separate duct to
supply fresh cooling air for just that reason, long term reliability. On
that engine the alternator was pretty close to the exhaust header also.
As I recall, the old generators which did the "rectifying" or "switching"
with the brushes and the commutator on the armature (which is nothing more
than a bunch of rotary switches) was far noisier electrically than the
alternators. But on the cars they were used on there were little if any
electronics to be affected.
Tim
By the Way, we have the race car "up and running". We did one test session
and will do another in about a week then a school and we can go racing.
Thanks to all of those on the list who have provided assistance along the
way.
----- Original Message -----
From: "Jack W. Drews" <vinttr4@geneseo.net>
To: <fot@autox.team.net>
Sent: Monday, August 14, 2006 4:44 PM
Subject: [FOT] alternators
>I have a new alternator that charges the battery okay but it creates so
>much static that it interferes with the electronic ignition and the
>electronic tach. Just out of curiosity, what goes wrong with an alternator
>to cause that?
>
> uncle jack
>
>
> ------------------------------------------------
> No Virus Found In This Message
> Scanned at barracuda.geneseo.net
>
>
> === Help keep Team.Net on the air
> === http://www.team.net/donate.html
|