three phase motors to steppers

[bamcknig at postoffice.syspac.com]

steve

Several years ago I was trying to use alternators for stepper 
motors and variable speed motors.  I managed to get Don Lancaster  a 
little interested and he wrote it up in one of his many columns.
One reply was from a guy using them to control a wood lathe.  He made 
up a video of his work which was very well done.  I don't remember 
what devices he was using, but the controller was physically large.  
I have been waiting for some low voltage Hi current mosfets, but that 
doesn't seem to be the way industry is going.   All the devices I am 
familiar with are in the under 100 watt range, or are much higher 
voltage.  The drivers have been around for ages, but getting them to 
control some power seems to the problem.  At High voltage and high 
prices, there seems to be a wealth of devices.  I seem to be twixt 
and between.
I'm not sure how a three phase induction would work as a stepper.  My 
immediate reaction would be to use it as a servo with feedback.  The 
alternators were nice in that you could control both rotor 
current,for torque, and your field for speed or position.  
I ended up putting some steppers on my mill.
The 72 rpm slo-syns can be used as steppers if you don't want a lot 
of speed.  They got gobs of torque and they are cheap.

This is all off the top of the head, if you want more details, I'll 
look a little deeper.

Bob McKnight
Phx AZ