FAQ: How to size stepper-motor power supplies?

Stepper motors are sensitive to the performance of their power supplies. Stepper motor power supplies can affect:

• Rate of motor heating — read FAQ: Aren’t heat and noise common stepper motor problems? for more on this
• Acceleration — read FAQ: What are the requirements for a stepper acceleration?
• Torque — read FAQ: What kind of torque can I get out of a stepper motor versus other options?

Plus there are times when it’s necessary to limit current supply to the motor. Read FAQ: How to set a stepper motor’s current limit and why is it important? for more on this.

When sizing a power supply, keep the above points in mind and remember that the drive type and method of operation influence which power supply is most suitable. Read FAQ: What is a stepper driver and how do they work?

When sizing a power supply, ensure that enough power is available when needed — but remember that an overly large supply wastes power.

Note that when it comes to a motor’s rated voltage versus voltage supply, there’s not much concern unless the power supply runs near the drive’s maximum rating. If this is indeed the case, then there’s a risk when decelerating the motor. The load’s momentum stores energy that must be dissipated. The drive can’t do this, so the energy returns to the power supply. This in some cases can overload the power supply and make it fail. So ensure the power supply has a rated voltage well above the motor’s rated voltage. Note that back EMF can also serve as a sort of feedback or gauge of how the motor is running if needed.

There’s additional reason to ensure that voltage is sufficiently high. As the motor draws more current, voltage in unregulated power supplies drops. This can degrade motor performance. In contrast, regulated power supplies provide stable voltage —is useful for applications with high-speed operation.

In the end, specific power-supply types from different manufacturers require specific analysis for sizing. Refer to documentation and always contact the manufacturer with questions.

Edited by Zak Khan || More information on this topic is also available from Teknic’s article detailing various power-supply options for stepper and servomotors • Gecko Drive’s article on power supplies • and GitHub’s Stepper Motors and Power Supplies feature.