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Re: Sync motor mod & Remote phase cntrl

     Richie,
     
     I don't understand.  Your 1/8 hp motor turns a 7" disc easily, but 
     your 1/2 hp motor is underpowered with a 7" disc?  That seems sort of 
     counter-intuitive.  Is it because you only put two flats on the 1/8 hp 
     motor?  Did that give you more torque than you would normally have 
     had?
     
     paul
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Subject: Sync motor mod & Remote phase cntrl
Author:  Tesla List <tesla@pupman.com> at INTERNET
Date:    3/23/00 10:32 PM


Original Poster: "R.E.Burnett" <R.E.Burnett@newcastle.ac.uk> 
     
     
Hi Mark,
     
Regarding machining your sync motor:
     
I machined a 1/8th horse 1425RPM rotor down a while ago to run a 1500RPM 
synchronous rotary.  I only machined TWO flats,  (4 is really the correct 
number you should use for a 4 pole machine though.)  This motor has plenty 
of power to turn my 7" phenolic disk with electrodes.  Even with only 2 
flats I can only just induce a pole slip by pressing on the disk edge with 
a finger.  At its rated supply voltage it slips just before the skin 
starts to burn ;-)
     
     <snip>
     
I am currently modifying a 1/2HP 2950RPM motor for 3000RPM use,  and have 
the same problem as you.  This motor can barely hold a bare 7" disk in 
lock at 3000RPM,  and I have reached the point where removing more metal 
will cause a noticeable decrease in staring torque.  The only solution I 
see in these situations is to use a smaller disk or over-volt the machine 
slightly to coax a little more locking torque.
     <snip>
                                                        -Richie,