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RE Re: Variac vs. Fan spe

Subject:   RE Re: Variac vs. Fan spe
  Date:    Sat, 3 May 1997 00:56:43 +0500
  From:    "Alfred A. Skrocki" <alfred.skrocki-at-cybernetworking-dot-com>
    To:     Tesla List <tesla-at-pupman-dot-com>


On Thu, 01 May 1997 20:01:28 GMT Robert Michaels
<robert.michaels-at-online.sme-dot-org> wrote;

>         You are =so= close to the truth - it's a pity you don't get
>         the cigar:

Thats ok Robert, I hate all tobacco smoke! Ironicaly I used to be a 
moderate to heavy smoker and I tried to quit for close to 30 years!
(I started when I was 9 years old) I had to go into a coma to get off 
the suckers, I sware there more addictive than heroin! I havent 
touched any tobacco products in almost three years AND I DON'T MISS 
IT ONE BIT!
 
>         Variable-frequency drives (VFDs)  (more modern name: vector
>         drives) are best used with (and intended for) 3-phase
>         motors.  Such motors have no centrifugal switch and no
>         special starting windings.  With a VFD their speed can
>         typically be controlled from 0.1x to 2x the nameplate
>         rating.   It's possible to run single-phase motors with
>         a VFD but inadvisable for reasons stated.

Actually synchronous motors like what used to be used in old turn 
tables and clocks work admirably with VFD, many amateur astronomers 
build their telescope clock drives (to keep the telescope pointed at 
an object for a prolonged time) with synchronous motors and use VFD
to adjust their speed for planets vs stars or the moon.
 
>         The best quick-and-dirty source for universal motors with
>         good speed characteristics is to salvage one from an old
>         vacuum cleaner.
> 
>                 Such motors can also be begged from vacuum
>                 cleaner repair shops in the same manner as
>                 neon transformers.
> 
>         They can be controlled as-is by means of a Variac, or
>         with a dc power supply + Variac a very fine degree of
>         control may be realized.

Lets not forget old AC power tools; drills, circular saws, ect almost 
always used universal motors. Universal motors also work very well 
with the triac phase shift controls commonly sold as light dimmers
and they are very inexpensive!

                               Sincerely

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                           Alfred A. Skrocki
                   alfred.skrocki-at-cybernetworking-dot-com
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