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RE: [TR] alternator problem 74 TR6

To: <triumphs@autox.team.net>
Subject: RE: [TR] alternator problem 74 TR6
From: "Randall" <tr3driver@comcast.net>
Date: Wed, 18 Oct 2006 16:46:35 -0700
> Indeed, running the system with the battery disconnected is a recipe for
> disaster.  But the question was running the alternator disconnected
> from the rest
> of the electrical system.  Without the load aps and load dumps there will be
> no spikes and the alternator is under no serious threat.

The OP said he measured the output at 17 volts.  That says it was generating,
which means the regulator was supplying rotor current.  Alternator regulators
are switch-mode devices, meaning it supplies either full battery voltage or none
at all to the rotor.  With full battery voltage applied, the rotor stores a
magnetic field, which takes time to decay.  Hence there will be spikes, every
time the regulator switches off.

Now maybe those spikes won't be big enough to cause a problem, depends on how
quickly the regulator switches and how much inductance there is in the rotor.
But at the very least, they will be applying more stress to the regulator than
usual, and it's the only thing between you and disaster.

Randall


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