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Power Supply Sizing With Multiple Motion Control Drivers

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  • Power Supply Sizing With Multiple Motion Control Drivers

    Good Day,

    I'm currently working on a project that will use (8) 24VDC motion control drivers.

    I am trying to figure out how to size the power supply to handle the following total values from the manufactures specs:

    Load Current: Rated: 28.15A Max 36.15A
    Inrush Current: 68.1A

    My questions would be:
    1. If I size my PS to the MAX 36.15A (40A PS) will the PS handle/manage the 68.1A inrush current without going into protection mode? As I understand it this is from charging up the capacitors in the controller.
    2. Is the 36.15A what I should be sizing my PS to?
    3. Anyone know where I can find a 40A PS with input power of 208V 3Ph? The lowest input voltage I can find for a 40A is 320V. if I must I can run (2) 20A or 24A and split the controllers up but was trying to avoid as I will already be running a separate PS for all the other control components.

    Thanks in advance!

  • #2
    If the inrush current in the motion control drivers causes a problem, then you could turn the power on in to them say two or four at a time.


    • #3
      These can operate in parallel mode to give you 50A. They also supply 110% constant current. Lastly, you could sequentially turn the drives on in groups to avoids over-current issues if needed like RogerR mentioned.


      • #4
        RogerR and Adisharr, Thank you for your input and recommendations. I think I may do a combination of both, utilizing the PSUs that can be connected in parallel and relays to control the ON time.

        I checked the specs on the controller and it says the inrush current lasts ~5ms.

        The spec sheet on this relay says response time is 20ms. I'm wondering then if it would just be possible to drive one relay coil off the first relay contact and "smooth" the startup without having to put any logic into it?
        Last edited by Swervomotor; 06-18-2018, 08:57 AM.


        • #5
          I would oversize your power supplies by a considerable margin if you are planning on using these switching supplies with motion control such as steppers and servo. There are many articles on how the transients from these types of motors dont play nice with switching supplies, which is one reason you see power supplies built for motion control having a good amount of capacitors on them. Motor transients can cause switch mode power supplies to trip overcurrent protection. These little PSUs dont usually have the bigger caps needed for large transient current draw. But as long as the power supply is rated well enough, you wont get any performance penalty for using a switch mode supply, its just the transient draws you need to be worried about.

          If you run dual or tripple PSUs in parallel, then you want some type of system where you can detect a failed supply and do an emergency stop and shutoff of your drives. If a supply fails and you only have enough current for your system with both PSUs running then the drives will overdraw the one PSU that is left and can cause another failure because of it. Also, when using parallel supplies, use wiring coming from the power supplies that are the same length, if one is much shorter distance than the other then it will try drawing more current from the closer supply instead of drawing equally.
          Last edited by MikeN; 06-18-2018, 01:55 PM.


          • #6
            Thank you for the information on switching PSU and motion controllers. I found a 24VDC 104amp Power supply that will allow me to run only 1 PSU in the control panel and give me some oversize for the future.