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Re: going salient

Hi Michael,

At 09:48 PM 9/10/00 -0500, you wrote: 
>Yes, It's me again...
>I've been sifting through all that info on converting to salient pole and I 
>found some "different" methods.
>It's come to my attention that the "dead pole method" is no longer used. Why 
>is that?

I have always gone by the plans like:


These plans cut the armature down so that it will draw close to it's full
rated current.  John Freau has experimented with more modest cutting with
great results.

>How do I calculate the part of the armature to remove? I probably won't be 
>using an angle grinder, but rather a milling machine so I'd like to know 
>exactly how much material to remove. Oh, I guess I should mention that all 
>the motors I'll be converting are 3450 RPM

I have never done a 3600 RPM so I'll pass to those that have been there.

>with horsepower ranging from 1/15 all the way up to 1/4. 

At 3600 RPM you are moving a lot of air and such.  I would think 1/4 HP
might be the minimum.  My 1/4 HP 1800 RPM motors turn big windy disks fine
but I think the torque goes up dramatically with twice the speed.

>Do you think I could get away with running 1/6 hp motor for a 10" diameter 

I "think" so ;-)

>I want a rotary that can handle up to 4kW and maybe even 6 in the not so 
>distant future... Does a 10" disk sound about right?

You need to have very good voltage stand off between the electrodes and
"hot" parts, and the disk rotor.  Then you need to be able to hold the
electrode hardware very securely.  I think 10 inch would be fine with a
good solid disk.  My gap below uses a 8 inch x 1/2 inch thick LE phenolic
rotor.  It is spinning long electrodes ferrites and cooling disks but at
only 1800 RPM.  It runs cold at 1kW and I would not worry at all about 4kW.
 You would only have two electrodes but they would be spinning very fast.
Be sure to think about shielding the rotor incase something flies off.

>How much dwell time should I aim for when using a LTR 2kW system?

3.5 mS seems to be a very consistent number there.  That is the time from
the AC zero current crossing.  You can make a scale like I have at:

and set the timing with the strobe light at:

Or...  You can just simply set it to get the longest arcs ;-)

>So many questions, so little time. Any help would be appreciated.
>I wish someone could just write a method that could be considered the 
>standard in this area...

The syncmot.zip is pretty standard.  It takes some careful study but it is
really good.