Power supply for 4 Nema 17 stepper motors


I’m building a test installation for a school project. It must work automatically so I'm using 4 NEMA 17 (43BYGHW811 http://www.wantmotor.com/product/42byghw.html) stepper motors. The drivers I will be using are the M542 from Leadshine. The input voltage of these drivers must be between 20V and 50V, I will use 24V. But now I am wondering how much amps the power supply must be able to deliver?

The 2.5A rating is usually per coil and there are two coils in each stepper. So your power supply should be able to make 20A continuously. Fortunately with good stepper drivers, the current does not peak any higher than this so you don't need to add any headroom on top of this figure. In practice, the continuous current will be less than this, because the stepper driver acts as a DC-DC converter and the current through the motors is greater than the supply current because the voltage is lower.

This is a rather large power supply. What are you doing that needs the power of this many large motors?

There aren't any stepper drivers on the hobby market that will handle 2.5 amps/coil. The best you can do is about 1.5 amps/coil, without additional cooling.

If you need more current and torque you will need to buy an industrial stepper driver.

That motor seems to be rated at 2.5amps and 3.1v or about 8 watts per coil or about 16 watts per motor (maybe say 20 watts to give a little slack). That suggests a 24v power supply with 4 amp should be just sufficient for 4 motors. I suggest you go to about 6 amps so the power supply is not being stressed.

I don't think the power supply needs to supply 20 amps - or 480 watts at 24v.

@jremington I believe the OP has already chosen "industrial" drivers.

...R Stepper Motor Basics

The motor power is the same as one coil's rating because with microstepping the coils are in sinusoidal quadrature and the power doesn't vary with step state. Most NEMA17 are about 4--5W, this one is a whopping 8W so it has high-temperature insulation and magnets I think. Anyway it will run really hot at 2.5A, consider running it at 2A instead.

If each motor takes 8W stationary, thats 32W, so allowing for motor driver losses thats about 50W needed so 2A at 24V. For any speed though, the power taken will rise, so lets say 3A or more is reasonable. The extra power overcomes back-EMF, ie its mechanical power delivered to the load, so it will matter how much load there is as well as speed - exact calculations are not easy...

BTW if those motor drivers aren't discrete-MOSFET designs the losses will be a LOT more, does anyone know if its discrete MOSFETs? The difference is a discrete MOSFET driver will run cool, not super-hot.