Is my voltage too high for motors?

[johnt]

I bought motors, power supply components and geckos, not as a kit, but supposedly "matched", if you will, for compatability.
I am wondering if my DC voltage is too high for the motors... they seem pretty hot to the touch.
There are no markings on the motors but the documentation that came with them shows the following:

Holding torque:640 oz/in

Rated current/phase(amps dc): 5.5

Phase resistance:0.42 ohms

Induction(mH) 3.5

The rest is from my own calculations...which could very well be wayyyy off:
5.5 amps X 0.42 ohms=2.3volts...(rated voltage???)
2.3v x 25(the maximum factor over rated voltage)=57.75v
My power supply is putting out 68vdc.
Is that too high?
Recently one of my geckos went south. I was considering switching to one of the 4 axis systems available from several vendors.
Thanks for you consideration.
John

[Richards]

Your voltage is probably a little high. Try using the latest formula that Gecko has published: MAXIMUM voltage = 1000 X SQRT(Inductance). In your case, that means that the MAXIMUM voltage would be: 1000 X SQRT(0.0035) or 59V. Fifty-nine volts is going to run really really hot. I prefer to de-rate my power supplies to about 75% of the maximum so that I don't burn the skin off the tips of my fingers. So, in my case, having a power supply that output voltage closer to 45VDC would better meet my needs.

[johnt]

Thanks Richards for your reply.
Is there anything I can do short of getting a new transformer?

[Richards]

To change a voltage requires a transformer. I don't know of any way to do that except to buy another transformer.