Archive of the former Yahoo!Groups mailing list: Homebrew PCBs

Tom,
Thanks for the input that makes me want to finish my
new CNC machine even faster.

I would like to see the schematic you talked about if
you could email it to me. I will be trying to make my own
controller as I can't afford the Precise one at $3,600.

Derek

This is the info I got from Precise:

Hello Derek:

The SC 67 has a 2-phase motor, so you cannot connect it directly to the
three-phase output of a standard high-frequency drive. I think that you have
two options:

1. Purchase a special frequency converter from Precise that is able to
output two-phase directly. The model is the PCF 310, and price is $ 3,600.

or

2. Purchase a standard 3-phase frequency converter from another source (such
as Yaskawa), and you will also need a Scot-T transformer. This transformer
will converter the three phase output from the frequency converter to the
2-phase that the spindle needs. You will have to contact a transformer
manufacturer to have one specially made.

Connection of the motor will depend on which option you decide on. The motor
cable should have four motor leads and a ground (some very old models did
not have a ground lead). If your motor cable does not have a connector, use
an ohm-meter to identify two pairs of motor leads with roughly 0.5 ohm
resistance each. These are the two phases. If your cable has a connector on
it (normally a round, black plastic connector), phase one will be pins 1 and
3, phase two will be pins 8 and 11, and ground is pin #13.

The precise frequency converter will have four pins on an output connector
to connect the four motor leads to.

If you go with option #2, the Scot-T transformer usually only has three
output taps. In this case, you connect one motor lead (pin 1) from phase-one
to an outside tap, the other lead from phase-one (pin 3) and one lead from
phase-two (pin 8) to the center tap, and then the remaining lead from
phase-two (pin 11) to the other outside tap.



Good luck.