Re: [TCML] SRSG Rotor Mods difficulty

[futuret@xxxxxxx]

Phil,

I never use the dead pole concept when I modify my motors for
synch operation.  I use the proportion method.  For 1500 rpm
motors I use 4 flats at 0.25 as you mentioned.  For example a
2"dia rotor would receive 1/2" wide flats.

For 3000 rpm motors I use 2 wider flats.  If I remember
correctly, I made my flats 7/8" wide on a 2.1" diameter rotor
(possibly the rotor was 1.85" diameter).  My memory is a little
foggy here.  I think I have it written down somewhere.
I don't know if this width is optimal, but the motor gave
very good torque after it was modified and locked into synch
very nicely.  It was a 1/10HP motor.

Cheers,
John





-----Original Message-----
From: Phil Tuck (hvtesla) <phil@xxxxxxxxxxx>
To: tesla@xxxxxxxxxx
Sent: Sat, Aug 8, 2009 2:47 pm
Subject: [TCML] SRSG Rotor Mods difficulty



Hello.



Having successfully  machined a 1500rpm motor in the past, I now wish 
to do
a (UK 50Hz 240v) 3000rpm one for my SRSG.



Previously, with the 1500rpm and based on advice from this group, I 
measured
the rotor diameter and used one quarter of the measurement as the width 
of
the machined flat. Like  this:
http://www.hvtesla.com/images/tesla%20coil%20modding_motor.jpg

Yesterday I machined a 3000rpm bench grinder using the 0.25 formula and 
the
motor just hunted afterwards without reaching a constant speed. 
Increasing
the input to 270v did not help either. This motor was poor quality 
anyway so
has now been discarded for other uses.


I have since been advised however that the 3000rpm motors do not 
respond so
well to machining as the 1500rpm, and may need more material removed.

Unfortunately I am never able to correctly identify the 'dead' pole as
illustrated  at http://evolve000.4hv.org/tesla/tc2srsg.html My motors 
always
seem to differ to this.



I have now acquired a second 3000rpm motor (bench grinder)  which is my 
last
attempt for a while. This rotor is 2.128 inches diameter, the motor  
itself
being rated at 250Watts (1/5 HP maybe??)
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