Re: Motor Sync Problem

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "BunnyKiller by way of Terry Fritz <twftesla-at-qwest-dot-net>" <bigfoo39-at-telocity-dot-com>

Tesla list wrote:

> Original poster: "Ryan Phillips by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <xanth-at-voyager-dot-net>
>
> List,
>
>     I've been working on making my first SRSG and I'm running into some
> difficulties.  The motor I am using is a brand new Emerson 1/3 H. P. at 3450
> RPM.  It's really very basic, CCW rotation, no start cap, two wires is all
> there is to hook up.  I took it apart and measured the diameter of the
> armature to be 2.810" and the distance between dead poles (or my best guess
> of dead poles) to be .75".

SNIPPERZZ>>>


Hi All....

Once again we are plauged by the flat mill width of rotors  :)  ......

here is an old post from about a year or so ago that I will "repost"

Hi All...

Ive been following this thread and my curiosity got the best of me ...  so
I went to school (
U.N.O. ) and asked one of the Mech. Eng. in Electrical motor design about
modifications.

the results of the conversation ended up as follows.

cutting flats are better in the long run for stability and startup ( cap
start types)
Vcuts are good for low start torque motors but can loose sync easier

the width of the cut can depend upon 2 items
the design of the case windings ...   dead pole or non dead pole
( if there is a point at which the windings are formed away from each other
this can be considered
a dead pole area. , and then there is the true dead pole area , this is in
which there is a lack
of windings in the core slot.)

as far as cutting the rotors a formula was derived for simplicity

a 38 degree arc ( for non dead pole windings) is suggested

a 40 degree arc for true dead pole windings


the 38 degree arc formula is...
this will determine the WIDTH of the cut made upon the rotor

2 X (sqrt(R^2 - (R X .9455)^2))
(( the .9455 = the cosine of 1/2 of the arc angle))

the 40 degree is ...
2 X (sqrt(R^2 - (R X .9397)^2))

for a 38 degree cut...
example    we have a rotor of 3" diam.    therefore the R =1.5"

R squared = 2.25        (R X .9455) squared  = 2.011

2.25 - 2.011 =  .23385

the square root of  .2385 = .4884

this multiplied by 2 = .9768" width of the cut made to the rotor


hope this helps ...


Scot D

PS   this works for both 1725 and for the 3450 rpm motors

thus....

2.810/2=1.405 ( radius)
and more thus...  ;)

2X(sqrt((1.405)^2  - (1.405X.9397)^2)

2X (sqrt(1.974 - 1.743))
2X(sqrt(.23))
2X.48
= .9609

soooooooo   the flat width of a 2.810 dia. rotor for a 3475 rpm motor with
a dead pole stator is...

TADA ........  .9609" wide....


Scot D