Re: [TCML] SRSG Rotor Mods difficulty

[futuret@xxxxxxx]

Phil,

I'm following up on my last posting here.  I looked up the
specifications for my synch motor modification.  It turns out
that the rotor was 1.875" dia. and I cut the 2 flats 1.062" wide.
I modified that motor on January 28, 1995.

My guess is that the flats could have been a little narrower,
and the motor probably would have worked just as well.
So yes, I made the flats much wider for a 3000/3600rpm motor
than I would for an 1500/1800 rpmm motor.

Cheers,
John


-----Original Message-----
From: futuret@xxxxxxx
To: tesla@xxxxxxxxxx
Sent: Sat, Aug 8, 2009 9:24 pm
Subject: Re: [TCML] SRSG Rotor Mods difficulty


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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