View Full Version : motor speed control

05-26-2008, 02:36 PM
I have a 60-odd-year-old Gorton vertical mill, 9x32 table. It's about 4/5 the size of a Bridgeport, and came with micrometer downfeed for the quill and a second motor and change gears in the knee to move the table. It'd be a pretty little thing, if some previous owner hadn't painted it with lumpy greenish-pink paint that looks like used kitty litter mixed with barf.

When I got it in 1993 I ran into the "three phase at home" problem. I replaced the three phase motor with a 2hp single phase, which has worked, but I'd like for the table motor to work now. And now that I have a big rotary convertor, there's no reason not to make it work... except the big (2x3 feet?) box full of contactors and relays has slunk away after all these years.

I still have the original three-phase spindle motor. Oh, there's a third three-phase motor, for the coolant pump setup.

Ssoooo... my options are:

a) convert the table and coolant pump to single phase

b) buy a carload of contactors and rewire it all back to three phase

c) get fancy and go for variable speed motors

How could I go about getting variable speed out of the three phase motors? Or would it be better to go to single phase, or even DC?

05-26-2008, 02:55 PM
Simple, use a VFD for each of the 3ph motors that you want speed control on.

05-26-2008, 02:57 PM
Easy, use a VFD. (for each of the 3ph motors that you want speed control on.) ;)

05-26-2008, 10:39 PM
Looks like a concensus!

Forrest Addy
05-26-2008, 10:44 PM
I suggest a VFD too. Does that make ir "consensuser"?

Can't beat them VFD's for making a real controllable motor out of a plain vanilla single speed boring tedious three phase motor.