Sigma stepper motor

[Dan000]

Good day to all of you out there.
I have a question regarding a tepper motor. I hope someone can help.
I have a Sigma Instruments stepper motor model no. 20-3437D200-B038. It is a 4 wire, bipolar version, with 0.7 ohms per winding. It has a diameter of 85.5mm and is 93 mm long. It was used in a Hewlett Packard reel to reel tape drive, back in the 1980's, as far as I can remember. It is vertually brand new and I want to use it in a surface grinder for the cross movement. The info missing are the voltage and current rating. Any help on this will be highly appreciated

[RomanLini]

It's a size 34 stepper motor, and since it is 1980's model it is probably round motor frame?

If so that means it is not a hybrid type. The length of 93 mm makes it likely a "double stack" size, or the "middle" size.

So knowing that it is a round style size34 double stack you can compare to other motors to get the typical watts per phase, which from memory I think is about 14w/phase for that motor.

Assuming your measured 0.7 ohms is accurate (as it can be a little tricky to measure) you need about 4.5 amps to give you 14 w/phase;
W = I*I*R = 4.5*4.5*0.7 = 14.1W

If you are using a microsterpping driver you may be able to increase that a bit, to maybe 5A/phase.

As a safe ballpark figure I would start with 4A/phase and test the motor out in use, and if it runs cool enough maybe increase to 4.5A or 5A later.

[Dan000]

Originally Posted by RomanLini It's a size 34 stepper motor, and since it is 1980's model it is probably round motor frame? If so that means it is not a hybrid type. The length of 93 mm makes it likely a "double stack" size, or the "middle" size. So knowing that it is a round style size34 double stack you can compare to other motors to get the typical watts per phase, which from memory I think is about 14w/phase for that motor. Assuming your measured 0.7 ohms is accurate (as it can be a little tricky to measure) you need about 4.5 amps to give you 14 w/phase; W = I*I*R = 4.5*4.5*0.7 = 14.1W If you are using a microsterpping driver you may be able to increase that a bit, to maybe 5A/phase. As a safe ballpark figure I would start with 4A/phase and test the motor out in use, and if it runs cool enough maybe increase to 4.5A or 5A later.

Thanks for the reply. It is in fact a round motor, green in colour. Just by the way, in the mean time I found out that the motor was actually used in a Hewlett Packard model 1084 Liquid Chromatograph. From the hints you have given me, I now have a good starting point. Thanks again.

[RomanLini]

You're welcome.

Just another tip, once you have connected a few amps through a motor winding, you can measure the volts on the winding so you can easily check watts per phase as volts*amps = watts.

That is an easier and more accurate measurement than trying to measure the ohms as most ohmeters are not great for low-ohms motor windings. Good luck.