[Sneap] GVM needed for General IonX Tandetron

[Klaus Bahner]

Howard,
 
First of all you should find out why the motor has stopped working. 
Is it blocked mechanically, due to a defective bearing? -> replace bearing
Is the phase shifting capacitor defective -> This is the most typical
failure mode. Replace the capacitor and the motor will work again.
Are the windings OK? ->If one of the motor coils has opened or short
circuited, check whether there is no overvoltage/overload on the motor
(without overload motor coils typically last forever) and get the motor to
the next motor repair shop, where they will re-wind it for a comparatively
small amount of money. I did that with our GVM motor a couple of years ago,
because re-winding it was much cheaper than any new motor and saved me from
making any mechanical changes. And it took less time to re-wind the motor
than getting a new one - just one day.
 
By the way, precision bearings may improve your mechanical noise and jitter
performance of the motor, but will certainly have no effect on the lifetime
of the motor. 
 
Hope that helps,
Klaus
 
 
 
 
 
 



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From: sneap-bounces at tunl.duke.edu [mailto:sneap-bounces at tunl.duke.edu] On
Behalf Of Howard Evans
Sent: 16. januar 2008 22:26
To: Symposium of Northeastern Accelerator Personnel
Subject: [Sneap] GVM needed for General IonX Tandetron



SNEAPers: 

The motor in the Generating Volt Meter (GVM), used to monitor and provide
negative feed-back control of the terminal voltage in our 1.7 MV Tandetron,
has stopped working after only twenty-seven years. Does anyone reading this
message have a complete GVM assembly (including the weldment that attaches
to the side of the accelerator tank) they don't need? It doesn't have to be
in working order, although that would be nice. If we have to replace these
things every twenty-five or thirty years, I would like to have a spare on
hand.

Actually, what I really need right now is the motor. All I know about it at
the moment (before I open the tank later this week) is it is a split-phase
induction motor, with a 4 microfarad oil-paper phase-shifting capacitor,
operating on single phase 208 VAC. It is General Ionex Corporation part
number A-08723, which is probably meaningless in 2008, but may have made
sense to someone in 1981 when it was penciled into a drawing.

As someone posted earlier in this forum, regarding ordinary versus premium
bearings, we would like to invest in a motor with "premium" bearings in the
hope that the motor will operate for a longer period of time.

I tried using the terminal voltage monitoring tap on the voltage-grading
resistive divider to control the terminal potential... it seems to have been
designed for this purpose originally... but the results are not
satisfactory. The ion energy wanders at will and seemingly randomly. We want
to do an implant that will take several days to complete, but we cannot
spare someone to continuously monitor and re-adjust the beam energy and/or
position. So I need to get this GVM repaired or replaced as soon as
possible, if not sooner.

Howard B. Evans, Jr. 
Engineer, Materials Laboratory 
UES, Inc. 
4401 Dayton-Xenia Road 
Dayton OH  45432-1894 

937-426-6900 ext. 116 (office and voice mail) or ext. 121 (lab) 
937-426-5718 fax 

hevans at ues.com e-mail 
http://www.ues.com web site 

"Things should be explained as simple as 
possible, but not simpler." -- A. Einstein 

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