On Fri, 26 Feb 2010 14:44:17 -0700, "thermo102"
wrote:

I have a 6-wire motor which I plan to operate as a 5-wire motor. As such
I've found the two center tap wires and will treat them as a single wire
going to a supply voltage of 40.5 VDC. Measuring the resistance of the
coils gives me 2.2 ohms to each of the remaining wires.

The motor itself is rated for 2 A. Using i = V - (Rated A * motor R) /Rated
R yields a result of 18 ohms for a current limiting resistor.

The closest I can find (would like a power resistor) is 15 ohms which would
give 2.35 A to the motor. (17% over)

Will this overheat the motor?

The motor is on a desktop CNC machine run by a unipolar driver (???) and is
for the Z axis. Best guess is running short periods of time (30 seconds
max, but usually only a couple of seconds).

Or, can someone suggest a source for a 18 ohm resistor? (To replace an
Ohmite TCH35P7R0J resistor).

---
That's a 7 ohm 35 watt resistor, so if it was part of the old circuit
there might be more going on than meets the eye and an 18 ohm resistor
might not be what you want.

What more can you tell us about how you'll be driving the stepper?

JF