Don Dunbar wrote:

Today we took delivery of a 3 cylinder diesel make by Kobota. Installed

on this engine was the smallest alternator I have seen. It was 90mm in
diameter and 80mm from the pulley face to the back clear of terminals.
The output is 30 amps.

The fields look to rotate around the armature with pulley mounted to

the outer casing and the shaft fixed to the holding bracket.

I dont know what RPM it runs at but will try to take some phots

tomorrow and get more details.

This engine runs at 3600 rpm and at first glance the A section pulley

was only 50mm OD and the drive pulley was around 100mm. This puts this
alternater above 7000 RPM.

Regards Don

Mike Wills wrote:

Don,

  Alternators from various small garden tractors (Kubota, Deere, etc..)
have been mentioned here before as viable alternatives. Many of them are
permanent magnet alternators so require no field current to produce
electricity; a big advantage particularly as an emergency power source in
place of a second battery.
  Is the one you saw a pm alternator? What was the cost? I'm still
undecided about using the stock Mazda alternator that I have or going with
something like this.

Mike Wills 

Head lights in a car are the biggest single draw at a several hundred
watts or 15 to 30 amps.

Paul Lamar

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