1. ## Exceeding stepper voltages

I have (3)KL23H2100-50-4B 570 oz-in 5A 2.5MH Nema23 step motors.
When I take the square root of 2.5 and multiply times 32, I get a
power supply voltage of 50.6V.
I have an Antek 63 volt unregulated powersupply capable of 17 amps.
The 63 volts of the power supply are measured at the filter capacitors.
I am not sure what the effects of an additional 12.4 volts would
have on the motors. The drivers are KL-9082 and can handle
up to 80 volts. My question is can I use this power supply with the
above step motors?

2. Antek usually use Toroidal transformers, if it turns out to be a problem it is usually fairly simple to take a few turns off.
Approx 2T/volt.
Al.

3. Running them at higher voltages will cause them to run hotter. You may find that under load your power supply is closer to maybe 55V, which might be OK.
Just watch the motors to see how hot they are getting.

4. The overvoltage on the input will have almost no effect on the motors as they are current driven devices. Regarless of the input voltage, the driver will be trying to regulate the current to the motor.
BUT
The over voltage could be a real problem for the driver. You should make sure the peak voltage (measured with no drivers connected) is somewhat less than the maximum spec for your drivers.
The drivers will run hotter with increased input voltage since they have to dissipate the difference betwen the input voltage and the voltage across the motor X (times) the current to the motor. (Pdriver = (Ein-Emotor) x current).

Sage

5. Motor heating has two sources; current passing thru the wire resistance is one (I squared R) and eddy current losses (iron losses) is the other.

Eddy current losses increase with the square of the supply voltage (double the voltage and losses go up 4 fold).

The equation we generated (VDCmax = 32 times SQRT mH) gives the supply voltage at which a NEMA-23 motor case temperature rises to 85C. Go over that limit and the motor will be over its temperature limit.

Our equation is conservative. It assumes the motor is on its side on a bench and not mounted to anything. This is the worst case situation, one of the motor's four sides is on the bench-top and unavailable for cooling being on the bench, there is very poor convection cooling and there is no conductance cooling at all because the motor isn't mounted to a heatsink (the mechanism).

The only sure-fire way to know how it will get for you is to invest in a multimeter that can take a thermocouple type temperature probe. The way the motor is mounted to the mechanism will greatly affect temperature. Since this is all about keeping the motor at a safe temperature, it's not unfair to use a small fan (CPU cooler size) to keep the motor cool; they are very effective. Just never let the motor exceed 100C.

Mariss

6. I would like to thank all who responded to my question.
From your responses, this should work but I will keep a close
watch on the motor temps. Thanks again..