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Sync Motors, how to modify an induction motor for sync operation



---------- Forwarded message ----------
Date: Sun, 28 Sep 1997 14:25:42 -0600 (MDT)
From: Chip Atkinson <chip-at-pupman-dot-com>
To: tesla-at-pupman-dot-com
Subject: Sync Motors, how to modify an induction motor for sync operation 

From: 	FutureT-at-aol-dot-com[SMTP:FutureT-at-aol-dot-com]
Sent: 	Thursday, September 25, 1997 4:19 AM
To: 	tesla-at-pupman-dot-com
Subject: 	Re: Sync Motors, how to modify an induction motor for sync operation

In a message dated 97-09-25 02:01:32 EDT, you write:

<< Hello,
> 	Is it possible to explain over e-mail how one could modify an AC 
> motor to make it run sync.  I'm still a little confused about the flats 
> on the armature etc.  Do you need special machining equip.?  What type of 
> motor is easiest to modify?  Any help greatly appreciated thanks. 
 
> Radtke

Kevin,

Yes, the procedure is quite simple.  Perhaps you saw my post a few
days ago in which I gave the specs for modifying a 1/4 hp 1725 rpm
motor.

Generally, the smaller the motor the easier it is to modify because
there's less metal to remove.  1800 rpm will require 4 flats, 3600
rpm will require 2 flats.  A quarter HP 1800 rpm motor can be modified
using a large hand file, it's work, but it can be done.  Make sure the
flats are parallel to each other and  of the same width (which means
same depth also).  If four flats, they should be a nice 90 degree
spacing.  You can measure the width of the cut and uncut areas as
you progress to keep everything even.  This maintains the balance
of the motor.  If the motor vibrates like crazy when you're done, then
you may want to check the widths of the flats again.

Be sure you start with an induction motor, such as a fan motor, 
washing machine motor, sump-pump, etc.  These motors may have
a capacitor  for starting, or for start/run, but many have no capacitor.

You'll need at least 1/20 HP for a small rotor, but I like to use at  least
1/10 to 1/4 hp.   If your rotor is large or heavy, you may need a stronger
motor.

As far as the depth of the flats is concerned; if the armature is 3 3/8" dia,
and you need four flats, then the flats can be 1 1/8" wide, and the 
uncut areas 1 3/8" wide.   But if you need 2 flats to modify a 3450
rpm motor, then for a 1 7/8" dia armature, use flats that are about 1
1 1/16" wide.  If the armatures are of a different dia than what I
mention here, just use the same ratio of flat width to armature dia.

The flats extend the entire distance from front to back of the armature
lamination unit.  Let me know if the procedure is still unclear, or if you
need more information.

To verify sync operation, just attach a cardboard disc to the motor 
shaft, draw a wide dark line across the disc using  a magic marker,
run the motor at night, and use fluorescent lighting, the pulsing of
the fluorescent lamps will create a strobe effect with the spinning
disc, and the marker line will appear to be stopped.  If you run the
motor using a variac, you can see the exact point at which the motor
begins to lock up, you will also hear a peculiar hunting sound as the
motor begins or trys to lock.  Of course using full mains voltage the
motor should lock up almost instantaneously.
 
> p.s.  The other day my friend and I decided to wrap a basketball with 
> foil and see how it would affect our coils output if we used it as a 
> secondary terminal.  We were getting 14-15" discharges from the bolt 
> terminal, but the sphere reduced that to about 2"  :(  We of course 
> played around with re-tuning the coil but not much improvement was
realized.
 >Do you need to adjust the main cap. size when adding load to the 
> secondary with spheres and torroids?
  >>

Two possibilities here;  1, you may not have had enough tuning range,
you'll need more turns with the sphere in general    2, you may not
have had enough power to fully break out of such a large sphere.

you may want to try starting out with a 4" sphere and seeing how
that works and tunes, and gradually using larger sphere's to see what
happens.  

Hope this helps,

John Freau