User-agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:31.0) Gecko/20100101 Thunderbird/31.4.0
Have you tried running the motor as a capacitor run motor?
On the net, there are circuits for running three phase motors off a
single phase with a motor run cap connected to the third winding. I
don't know for sure if the motor would run synchronously with this
arrangement or not, but it would be relatively simple to try. Many
amateur machinists hook up one beefy freewheeling motor in this way to
generate three phase power from single phase for metal working
equipment. I don't see why you couldn't just use the freewheeling motor
alone to drive your gap.
Just to be sure to use motor run capacitors, and not the much cheaper
motor start capacitors. Usually, run caps have deep drawn aluminum or
steel cases, like microwave oven caps, while start caps usually come in
plastic cases. Motor start caps will overheat and fail spectacularly if
run for more than a few seconds.
Generally, these arrangements use a larger capacitance value to get the
motor up to speed, and then you drop out part of the capacitance for a
smaller value for the steady state run condition. You can use a relay
controlled with a manual start switch to implement this function.
Dave
On 1/26/2015 12:07 PM, twoten wrote:
I'm trying to find a 120v 1200rpm synchronous motor to spin my 6
electrode rotating spark gap. I have a 1200 rpm synchronous motor but
it's 3-phase and 230volts. I have been looking into microcontroller
solutions and building my own 3-phase motor driver. I have a vfd that
can spin the motor at the proper rpm but the phase drifts slowly around
the clock as seen by my homemade 120hz led strobe light.. Existing vfd's
don't have inputs for zero crossing signals and so can't be phase locked
to the line. If anyone knows where I can find a motor or even if they
exist please let me know. Thanks in advance!