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.
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
Does anyone have any suggestions or knowledge of the correct
way to start this type of motor? Or maybe the motor has an internal