[NLRS] re: turn that alternator faster

Wed, 15 Jan 2003 08:11:08 -0600

Just keep in mind, don't turn the alternator TOO fast, I have seen cases
where the alternator came apart and exited the engine compartment, stage
left.  Admitedly it was a race car situation.

If you keep the alternator under 10,000 rpm you probably are ok.  This isn't
based on an engineering analysis - just the knowlege that I ran an
alternator in my race car with the stock 1.5:1 ratio for years, and
regularly had the engine at 6500 rpm.

This is probably not an issue in someone's van - but we don't want someone
with a Mustang to double the alternator speed, and then go to the dragstrip!

73's Bryan

-----Original Message-----
From: [email protected] [mailto:[email protected]]On
Behalf Of Dr. Gerald N. Johnson, electrical engineer
Sent: Tuesday, January 14, 2003 9:46 PM
To: Steven H Sawyers (na0ia)
Cc: Duane Grotophorst; [email protected]
Subject: Re: [NLRS] Wanted - RF Concepts Amplifiers and/or Website

You don't generally need a special alternator to give 24 volts, just a
pulley to be sure to turn it faster and a regulator set for 24 volts.
E.g. a 2:1 voltage divider ratio at the sampling input.

There was a fairly good regulator circuit using an LM-723 in the Holiday
'76 issue of 73 magazine. I didn't prefer its use of the internal Zener
to drop the drive voltage to the pass transistor, I preferred to move
that power dissipation out of the chip, but otherwise the one I built
about that time was identical. I used mine to replace faulty Ford
factory regulator.

Several years ago I was experimenting with a Delco alternator and found
it needed to turn about 1400 RPM to self excite and then it produced
about 14 volts. With 12 volts on the field it would need to turn 1800
RPM to do 28 volts. Increasing the field voltage may eventually fry the
field, but would keep the speed requirement down.

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