Reply with QuoteUse this page to work out the wiring:
techref.massmind.org/techref/io/stepper/wires.htm then just run it at 1 amp, then 2 amps, then 3 etc... while keeping an eye on the temperature.
Sigma Instruments stepper
I have a Sigma Instruments stepper motor I got as part of a used 3-axis control system. It's a Nema 34 size, and the model number is 20-3424D-24450. The label is quite faded, but it looks like it was made in 1986.
I have Googled for information, but I can't seem to find any. I need to know its ratings, so I don't overdo the amperage. My drivers (PacSci 6410s) will do up to 5 amps, and if I can drve this stepper with that, I'd really like it. It is driving my BF20 mill clone, and is not strong enough at 3.75 amps to run it the speed I want.
Thanks for any help you can give me!
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Use this page to work out the wiring:
techref.massmind.org/techref/io/stepper/wires.htm then just run it at 1 amp, then 2 amps, then 3 etc... while keeping an eye on the temperature.
Thanks for the link. The motor came pre-wired and plugged, ready to go (used system, taken from a working machine), but the motor does not give the amperage rating.
How do I tell how hot "too hot" is? I have not used steppers before, so I don't know hot they get in normal usage. Feels warm to the touch? Can just barely hold it? Can't touch for more than a second or less?
Let me know!
Typically we are talking about the sort of heat that can damage coil insulation or damage the strength of the magnets. The insulation shouldn't melt below 100'C (unless the motor is /very/ cheaply made) and the magnet shouldn't be permanently damaged below 150'C. So, most likely, the motor can literally be boiling hot (100'C = 212'F = boiling point of water) without being damaged.Originally Posted by DSpeck
However, there is another issue: Any permanent magnet will loose strength (temporarily) as the temperature rises. In fact, they loose strength at room temperature or anything above absolute zero! Usually the amount isn't much, but it can have a significant effect if the motor is being pushed to it's limit in the application. For example, some types of magnets can loose 20% of their strength with each 100'C rise in temperature.
So the best thing to do is just work the machine under load to ensure it doesn't skip steps on that axis, and run it at the lowest current that works reliably while keeping the motor temperature well below boiling. Even while the motor stays below temperatures where it might be damaged, you will probably find that there is a point where more current actually results in less torque because the motor is over-heating. And running it at the lowest current setting that gets the job done seems wise to me in any case. If that motor can't do the job, it needs to be replaced anyway.
More on magnets and heat:
www.coolmagnetman.com/magstren.htm
Thanks for the clear explanation, James. I will try it on higher currents and see how it does. Being a 25 year old motor, it may just have a lower torque naturally, no matter how I drive it. I will likely replace the motors with the 570oz-in Nema 23s from Keling, but these are what I have for the moment, so I'll start with them to see how they do.
