Message-ID: <3A5F3278.5E34B773@regandesigns.com>
Date: Fri, 12 Jan 2001 10:36:08 -0600
From: Brent Regan <brent@regandesigns.com>
To: Lancair List <lancair.list@olsusa.com>
Subject: Re: Alternator brushes
Reply-To: lancair.list@olsusa.com
Mime-Version: 1.0

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After giving the alternator brush discussion some thought I wanted to bring
up a point that may have been missed.

One school of thought says that current carrying brushes in rotating
equipment actually ride on a hydrodynamic film of plasma. The plasma is
created in the arc of the current between the brush and the commutator or
slip ring. Wear only occurs when the brush touches the commutator due to
eccentricity, surface imperfection or imbalance. It also seems reasonable
that rapid, large changes in the current flow through the brush would
contribute to wear, either directly or through pitting of the brush or
commutator.

It would therefore seem reasonable to theorize that the voltage regulator
can effect brush wear. Older style electro mechanical regulators that
regulate alternator field current by switching on and off the full 14 volts
may cause accelerated brush wear compared to a solid state linear regulators
(e.g. B&C). Vintage WWII brush testers likely did not anticipate or test
linear regulators.

Anyone out there with anecdotal information on automotive alternators used
with solid state regulators in aircraft?

Regards
Brent Regan

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