I am running a bipolar NEMA 23 stepper motor rated at 2.8A/phase driven by a TB6600 driver, with a peak current rating of 4.0A. I have set the appropriate DIP switches to set the current output from the driver at 2.8A (RMS).
I am supply the driver via a bench top digital power supply that can output 30V and 5A and I have set the current to 2.8A, however the PSU only displays 1.4A at 9V, which is the maximum it can achieve in constant current mode before it switches to constant voltage mode. If I increase the voltage the current drops proportionally all the way down to 0.46A at 30V running in constant voltage mode.
Therefore I am not achieving the sort of torque output from the stepper motor that I require for my project.
Can anyone advise why the driver is not supplying the stepper motor's rated current?
I am attaching photos of my setup. Please note that I don't have the signal/logic side connected for clarity and because it should still draw the holding current. I have been controlling it successfully with an Arduino and have the same issue with the current.
Your TB6600 defines and limits the coil current. You cannot control that with your supply. The TB6600 works similar to a buck converter. The higher the PSU voltage, the lower the current it draws from the PSU. Regarding the PSU it is a matter of power, not of amps. You should not limit the current at the PSU.
N.B. The rated coil current is per coil. so the TB6600 delivers 2.8A to both coils.
I think that sets a peak current. The TB6600 adjusts actual current dynamically, in an idle state the current is probably reduced to a holding current.
I would try giving the motor some steps and see what happens to the current. You might need a scope rather than rely on the PSU display for that. Also, applying some torque to the motor might make a difference.
Where did You buy the TB6600?
I've bought a few, at low cost, because the label showing the dipswitch combinations is wrong for one current! Misprinted label!
Check the setting combination You use if the same combination exist for another current!
Finding the correct label from the datasheet, not the unit You have.
I have now put a multimeter in series with one of the windings to read the current. It is still drawing 1.5A when it rotates but, as you say that is regardless of the PSU settings, I guess all the fiddling around with the settings on the power supply just got me to what is actually being drawn by the motor. Maybe it is actually higher than what is shown on the multimeter due to averaging.
Thanks Railroader, that would have been an easy fix but unfortunately I have tried many switch combinations and they seem to correlate to the table.
ps. I have 2x motors and 3 drivers and the result is still the same when I try swapping them out.
Your stepper will draw more current if you mechanically load it up.
If the stepper is under no load, then why does the driver need to supply full rated current?
What is the part number of your stepper, please post a link to specs/data of the stepper.
Definitely. When the motor is rotating, the coils are switched on and off in fast sequence. You can try to rotate it very slowly ( about 1 step/sec ) so that you can sse the switching at the multimeter.
Not really, a stepper is not a DC motor. Usually steppers draws the most current at standstill. There maybe a slight current rise at the PSU because the needed power will increase with the load. But steppers are very, very ineffective, so this will only be a slight effect.
The driver - at least such cheap drivers as the TB6600 - don't recognise the load. They always try to drive the same current through the coils. And as far as I know the TB6600 has no automatic reduction of the current at standstill.
