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Re: [TCML] SRSG Rotor Mods difficulty


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.


-----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


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:

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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