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How to correctly connect stepper drivers to transformer.
How to correctly connect stepper drivers to transformer.
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08 Sep 2025 00:00 #334597
by langdons
I have a 3-axis CNC router machine with a toroidal transformer that has 3 separate secondary windings each 28.5VAC.
The transformer powers 3 fake DM860 stepper drivers, which each power a 4.6A (RMS) stepper motor.
Should I connect all windings in parallel and power the drivers from the combined power of all windings, or can I just connect each driver to its own winding?
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tommylight
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08 Sep 2025 00:44 #334598
by tommylight
To each it's own.
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There in no difference either way will work, but i like to keep things compartmentalized.
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08 Sep 2025 00:52 #334599
by PCW
Also you may do better performance wise by using 2 windings in series for all drives
so 57V rather than 28.5V (assuming the drive is OK with 57VAC, )
28.5V is roughly equal to 40 VDC and 57V is roughly equal to 80VDC
You would get better high speed performance with the 57VAC
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08 Sep 2025 12:32 #334617
by langdons
PCW, that's how it is now.
X and Y get 57VAC.
Z gets 28.5VAC
Tommy, you would opt for the one winding per driver isolated winding approach?
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08 Sep 2025 12:43 #334618
by langdons
The real problem with 57VAC is the drivers get a bit hot.
The driver for the Z axis has only 100V filter caps, the X and Y axes have 200V caps.
Current wiring scheme:
2 windings in parallel drive the Z axis driver, another winding doubles the voltage to feed the X and Y axes 57VAC.
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08 Sep 2025 15:15 #334631
by tommylight
Since the drives can handle it, i would stick with PCW's advice.
Do not worry much about drives getting hot, if you can hold your hand on the cooler they are still far from what they can handle, and just in case, if you touch them and a piece of your skin remains attached to them this would be when you start to worry.
50-60 degree Celsius to us humans seems like it is burning, 80 feels like it burns the soul, not the hand.
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08 Sep 2025 15:43 #334635
by langdons
OK.
The X and Y axes shall powered by 57VAC (all the drivers have an internal rectifier).
Should the Z axis have its own isolated winding, or should it remain powered from one half of the 57VAC supply?
The z axis does not move often, it uses less power than the other axes.
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08 Sep 2025 17:34 #334643
by tommylight
Leave it as is.
Wire stuff, make stuff move, make chips...and post pictures and videos.
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09 Sep 2025 15:33 #334714
by langdons
I shall leave it as is, unless some good reason to change it arises.
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How to correctly connect stepper drivers to transformer.
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