Re: Starting a Teletype sync motor question

In a message dated 6/1/99 11:23:41 PM EST, tesla-at-pupman-dot-com writes:


  I have several smaller sync. motors from 8" computer drives which are all 
permanent capacitor, split phase using around 5 uF to run. Small induction 
motors are very forgiving of capacitor values.  It should state on the motor 
if it requires one (assuming the label is readable).  It uses 2 separate 
windings which have one end of each bonded together inside.  Both are run 
windings, but the winding that has the higher d/c resistance should be the 
cap. winding. The common winding wire to neutral  and one side of cap, the 
higher resistance winding to the other side of the cap, and hot to the lower 
resistance winding.  The color code for my particular motors were, blue = 
cap, black = common & cap, black/yellow hot.

  Incidentally one of the motors acted as yours did, I had to hand start it.  
It also was 60/50 Hz 3600/3000 R.P.M. and ran OK after repair.  The problem 
was an open in the cap winding which was repairable.  If you can see a 
centrifugal switch inside the motor, and it has 3 wires, it probably is a cap 
start, induction run, but wired the same.

Kevin Eldredge

 I'm using a 50Hz, 3000rpm 1/12th HP Teletype sync motor on 60Hz,
 for 3600rpm in a rotary sync gap.  I tried connecting a 7uF to 30uF,
 cap across the blue and red wire for starting, but it won't start this
 way.  Yellow and blue are connected to the line.  I then touched the
 red and blue wire together with no cap for starting, this works better,
 but the motor still often needs a push to get going, and it makes
 clanking noises as the speed ramps up.  Once it reaches max
 speed, I disconnect the red wire, then it locks up fine.  I've been 
 using this rather awkward method for starting it.
 I realize that Teletype motors usually use an external relay block
 for starting, but different motors seem to be wired a little differently?
 I wonder if the 60Hz on a 50Hz motor makes the starting a little
 more difficult?
 Does anyone have any suggestions or knowledge of the correct
 way to start this type of motor?  Or maybe the motor has an internal
 Thanks, >>