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IndustryArena Forum > CNC Electronics > Stepper Motors / Drives > Another power supply size question
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  1. #1
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    Another power supply size question

    Hi
    I intend to get 3 of these https://www.omc-stepperonline.com/1-...or-driver.html

    and run them with a 36 volt power supply. How much current should the power supply be able to handle. Also would a switching power supply need to supply more current than an unregulated supply. I was thinking of using one of these https://www.omc-stepperonline.com/po...-s-500-36.html is this supply big enough.

    Cheers

    Andrew

  2. #2
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    Re: Another power supply size question

    Hi Andrew- You should read the data sheets. The motors are 5.8A and the PS is 14A. 3x5.8A is 17.4A. Since you wont run the motors at the same time and same duty you will not need 17.4A. 14/17.4=80% capacity. I think this will work. If it does not work it means that your motors will not be able to provide full torque. Depending on what you are doing this maybe good or not. There is no difference in a unregulated vs regulated at a simple level. Go for it and keep us posted on results. Peter

  3. #3
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    Re: Another power supply size question

    Hi,
    To work out the current needs, multiply the rated current of all thee motors by 2/3.

    Cheers
    Peter


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  4. #4
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    Re: Another power supply size question

    I would go the full 48v using 2 supplies myself.
    Put a 12A on the X & Y.
    Put a 10A on the Z.
    Will give you the opportunity to get the full grunt from the systems.
    Just like these:
    https://www.cnc4you.co.uk/Breakout-B...U-48Volt-12Amp
    https://www.cnc4you.co.uk/Breakout-B...U-48Volt-10Amp

    Then because you'd have extra capacity available from the 10A on the Z. I'd prob then use voltage step downs to power the drive boards (ie: 5v, 12v, 24v) from there.

  5. #5
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    Re: Another power supply size question

    Quote Originally Posted by dazp1976 View Post
    I would go the full 48v using 2 supplies myself.
    Put a 12A on the X & Y.
    Put a 10A on the Z.
    Will give you the opportunity to get the full grunt from the systems.
    Just like these:
    https://www.cnc4you.co.uk/Breakout-B...U-48Volt-12Amp
    https://www.cnc4you.co.uk/Breakout-B...U-48Volt-10Amp

    Then because you'd have extra capacity available from the 10A on the Z. I'd prob then use voltage step downs to power the drive boards (ie: 5v, 12v, 24v) from there.
    The driver manual recommends 36 volt as a supply voltage to stop problems with back emf ?

    Andrew

  6. #6
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    Re: Another power supply size question

    Quote Originally Posted by the great waldo View Post
    The driver manual recommends 36 volt as a supply voltage to stop problems with back emf ?

    Andrew
    Can't see too much trouble if cables are shielded.
    Anyway. Using the inductance formula I see around. It shows optimum voltage of 45v to get best power from motor.

    You can always tweek the 48v supplies down a little.
    If you use 36v and are anyway disappointed it's not like you can turn them up.

  7. #7
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    Re: Another power supply size question

    Hi Great Waldo - The PS you have picked has a DC output adjustable 32-40V so you have that to play with, I'd go at 40V. Back EMF is usually an issue with lower voltages then 30V with this sort of system or with large decelerations. The higher the voltage the better the performance vs back EMF at higher speeds, low speeds back EMF is negligible. As we do not know what your desired speed range is I can't say if its a problem or not. The usual equation 32*sqrt (inductance) gives 46V max so if a 45-46V PS is there I'd pick that because it's still in the parameters of the Drivers (48V peak). But I don't think you will see a diff 40V vs 45V it will come down to the quality of the driver. Cheers Peter

    Edit - as you can read from the selected driver manual it recommends 36V for good reasons. So Start at 36V if high speed needs more grunt wind up the voltage to 40V. Use the lowest voltage that gets your job done because over voltage just means hotter motors that run rough. The rest of the driver manual looks good I think it's a good driver.... looking at the data sheets it charts the delta of 36V vs 48V so there's an answer if you need the extra torque at speed.

  8. #8
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    Re: Another power supply size question

    Hallo Peter

    Thanks for the reply.I think I shall go with the three 36 volt supplies. There is a 17.5 amp 36 volt supply available with pfc but it works out at about twice the cost.
    https://www.ebay.at/itm/Schaltnetzte...QAAOSwEMddjRHi
    A more elegant solution size wise. I shall have to a think about that. The debate is still open in my head. Also three seperate power supplies don't get so strained as a single, I assume?
    cheers

    Andrew

  9. #9
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    Re: Another power supply size question

    Hi TGW - Cost of units is relative to consumption volume so bigger units sell less and have more costly parts due to increased specs of components. A correctly speced single PS will perform the same as multiples. But go with the least cost solution. Also remember to correctly match the amps of the driver to the motor. When first running I suggest you set them low to be safe, then as you get the parameters of speeds/accelerations etc dialed in you can crank the amps up to matching values. 6A in the wrong wire creates a lot of smoke!! Its always an exciting time when you get all those LEDS lite up and motors moving....Good luck Peter

  10. #10
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    Re: Another power supply size question

    Thanks for the tips Peter. It'll be a little while before I can get all this together and I still have to assemble the cnc machine ( https://www.sorotec.de/shop/Portal-m...-DIY-4863.html ) It was a little bit pricey but everything was supplied. I don't have much space so at the moment i'm working with my old machine with acme threads which works but makes some horrible noises when running a bit faster. I want to get the controller and electronics all ready to go before I put the machine together and swap machines. Unfortunately I don't have a lot of free time so it's all a bit of a juggle.
    Cheers
    Andrew

  11. #11
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    Re: Another power supply size question

    Quote Originally Posted by peteeng View Post
    Hi TGW - Cost of units is relative to consumption volume so bigger units sell less and have more costly parts due to increased specs of components. A correctly speced single PS will perform the same as multiples. But go with the least cost solution. Also remember to correctly match the amps of the driver to the motor. When first running I suggest you set them low to be safe, then as you get the parameters of speeds/accelerations etc dialed in you can crank the amps up to matching values. 6A in the wrong wire creates a lot of smoke!! Its always an exciting time when you get all those LEDS lite up and motors moving....Good luck Peter
    Hi Peter
    I was just wondering would I need to use the tuning software for these drivers as there don't seem to be any dip switches to set the current on the drivers.
    Cheers
    Andrew

  12. #12
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    Re: Another power supply size question

    Hi TGW - Hi andrew you do need to read the data sheets Looking at the dip settings there is no current control. There is autotuning and other stuff. Cheers Peter

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