How do I determine how big of a power supply to use with my servo motors?


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Thread: How do I determine how big of a power supply to use with my servo motors?

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    Default How do I determine how big of a power supply to use with my servo motors?

    I have an older 90's era cnc mill I'm converting to Acorn control and I want to replace the power supply with one that I know works. My current power supply kinda looks like a fire hazard and one of its capacitors is very loose and wobbling around, I don't feel like I should trust plugging it in. My problem is, that there is no identifiable information anywhere on the power supply aside from the manufacturer that has long since went out of business. Same situation with my spindle drive servo motor, manufacturer is out of business as well.

    How can I determine what power source to use? The big spindle driver servo is a 30lb/in continuous torque motor with 15.83 continuous amps if that helps identify anything.

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    Attached Thumbnails Attached Thumbnails How do I determine how big of a power supply to use with my servo motors?-power-supply-jpg   How do I determine how big of a power supply to use with my servo motors?-big-motor-jpg   How do I determine how big of a power supply to use with my servo motors?-big-motor-tag-png   How do I determine how big of a power supply to use with my servo motors?-small-motor-jpg  



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    Default Re: How do I determine how big of a power supply to use with my servo motors?

    I just hooked it up and found there is 170 Volts DC (168.3 vdc) coming out of it. Not sure how to measure the amps right this second though. I guess my biggest concern is on the other side there is a solid state relay switch that I have no idea what its for and 2 really big 10 ohm resistors wired as separate components. I suspect the SSR and 10 ohm resistors are related but why I have no idea unless it's to somehow dump the capacitors power on shutoff.

    I'd feel so much more comfortable using a power supply with clearly labeled terminals and no mystery components.



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    Community Moderator Jim Dawson's Avatar
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    Default Re: How do I determine how big of a power supply to use with my servo motors?

    Please post a picture of the ''SSR''. I suspect what you are calling a SSR might be a bridge rectifier if it's on the back side of the PS board.

    Normally about a 10K ohm resistor would be used to bleed the caps of a 170V PS on power down. 10 ohm resistors might be used as an inrush current limiter, but that seems kind of high for that use.

    The real question is: Are your servo drives compatible with Acorn's step & direction control output?

    Jim Dawson
    Sandy, Oregon, USA


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    Community Moderator Al_The_Man's Avatar
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    Default Re: How do I determine how big of a power supply to use with my servo motors?

    There is apparently two Mosfets on the board Q2 Q3 they have G.D.S. Gate-Drain-Source.which is the termination labels used for Mosfets.
    Not sure why you would need any sophistication in a servo supply, normally all that is needed is a large linear transformer and bridge and caps.?
    What is the Kva of your present transformer?
    Al.

    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.


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    Default Re: How do I determine how big of a power supply to use with my servo motors?

    I feel like I made the classic new guy posting mistake and sort of answered my own question by posting a pretty convoluted one prematurely lol.

    After some thought on it last night about what is actually going on in this power supply circuit I think I will use it as is. My original concern about not knowing what the solid state relays do was worked out I think. What I think is happening here is there is a 5 pin connector on the bottom right of this power supply that leads to a 'axis shunt' terminal on the old motherboard, I think this works as an emergency stop. When the axis shunt is activated I think the second SSR (the one mounted to the black plate) activates and dumps all power into the 2 10 ohm resistors while simultaneously turning off the SSR (the one mounted on the white surface) supplying 110v to to the input terminal.

    AI: Now that you mention it, remembering a little bit (but not much) from school I think there are 2 mosfets thermal pasted to the black aluminum plate under Q2 and Q3 that the power supply is screwed down to. When I get some time I'm going to see if I can't get some numbers off of them to search for info. This machine has a transformer that allows either 220v or 110v to power it, I haven't yet really dove into thinking about it yet though. Right now I don't plan to use it as everything can be powered by 110v, that may change though.

    Jim: I sure hope my servo amplifiers are compatible! They are old Glenteck amps and look like they have the same pinouts as most other similar ones. I'll connect it all up an cross my fingers on a bench test latter this week. I'll post up some pictures. Late last night I was able to get in contact with an old employee that had a schematic of this power supply too.




    Attached Thumbnails Attached Thumbnails How do I determine how big of a power supply to use with my servo motors?-ssrs-jpg   How do I determine how big of a power supply to use with my servo motors?-capacitors-jpg   How do I determine how big of a power supply to use with my servo motors?-servo-power-supply-dm2800-jpg  


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    Community Moderator Jim Dawson's Avatar
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    Default Re: How do I determine how big of a power supply to use with my servo motors?

    OK, now the power supply makes sense with the schematic.

    If you can find the pinouts for the drives you'll be able to figure out the compatibility quickly.

    Jim Dawson
    Sandy, Oregon, USA


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    Community Moderator Al_The_Man's Avatar
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    Default Re: How do I determine how big of a power supply to use with my servo motors?

    The Glentek drives that I have come across were ±10vdc analogue input?
    What is the part No.?
    Al.

    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.


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    Default Re: How do I determine how big of a power supply to use with my servo motors?

    Quote Originally Posted by Al_The_Man View Post
    The Glentek drives that I have come across were ±10vdc analogue input?
    What is the part No.?
    Al.
    I have 1 SMA8115HP-0445-014A-1 and 3 SMA8110-0445-013B-1 Glenteck amplifiers. I had to send them an email to find the manuals, if I remember reading right they all have a 170vdc input. They were wired that way from that factory too so as is they hopefully will work with Acorn control. This should be a pretty straight forward retrofit if nothing unexpected pops up. I just finished going over with a good cleaning and replacing consumable parts on the mechanical side and all is really good there.

    3 servo axis amp manuals: https://www.glentek.com/download/sma...al/?wpdmdl=379

    and

    spindle servo amp manual: https://www.glentek.com/download/sma...al/?wpdmdl=357



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    Community Moderator Jim Dawson's Avatar
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    Default Re: How do I determine how big of a power supply to use with my servo motors?

    Your axis amps will not work with Acorn, they are +/-10V analog command signal input, and require an encoder to close the loop at the controller level. Acorn is step & direction only and has no provision for encoder feedback.

    Jim Dawson
    Sandy, Oregon, USA


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    Default Re: How do I determine how big of a power supply to use with my servo motors?

    Quote Originally Posted by Jim Dawson View Post
    Your axis amps will not work with Acorn, they are +/-10V analog command signal input, and require an encoder to close the loop at the controller level. Acorn is step & direction only and has no provision for encoder feedback.
    Well that sucks, this mill is a real money pit if that's the case. Are there in-between components that can adapt analog to step and direction input?



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    Community Moderator Jim Dawson's Avatar
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    Default Re: How do I determine how big of a power supply to use with my servo motors?

    Quote Originally Posted by setlab View Post
    Well that sucks, this mill is a real money pit if that's the case. Are there in-between components that can adapt analog to step and direction input?
    No, not as far as I know. I think the Centroid Oak, and the All-in-One DC both have analog control and encoder feedback. There are also some drives that would work with your motors that do accept step & direction control.

    As far as being a money pit, it just depends on what you want out of it. I wouldn't hesitate to spend $5K or so doing an upgrade if it is an otherwise nice machine. I spent around $5K upgrading my knee mill controls and close to $10K upgrading my lathe controls.

    Jim Dawson
    Sandy, Oregon, USA


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    Default Re: How do I determine how big of a power supply to use with my servo motors?

    ...this Motor Drawing may help you.
    Have to give the Ebayer some free advertisement
    https://www.ebay.com/itm/MCG-3572-MR...-/332360618961

    Attached Thumbnails Attached Thumbnails How do I determine how big of a power supply to use with my servo motors?-mcg-3572-motor-jpg  


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    Default Re: How do I determine how big of a power supply to use with my servo motors?

    Quote Originally Posted by machinehop5 View Post
    ...this Motor Drawing may help you.
    Have to give the Ebayer some free advertisement
    https://www.ebay.com/itm/MCG-3572-MR...-/332360618961
    Wow, that's surprisingly similar to what I have. Thankyou, I'll save that to my desktop.



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    Default Re: How do I determine how big of a power supply to use with my servo motors?

    I was just searching for other controller options that would work with analog input and came across a site called viper servo.com. Viper actually has a forum on the cnczone too surprisingly, they make a step direction servo controller in my price range ($179) that looks like a really good option. They also have a step/direction to analog output device that allows use of old analog servo drives with step and direction controls Step2Linear, ViperServo. For $90 too. If it works with Acorn I'll defiantly go this route if I don't learn anything else to dissuade me in my research.



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    Community Moderator Jim Dawson's Avatar
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    Default Re: How do I determine how big of a power supply to use with my servo motors?

    It looks like the Viper Step2Linear would work with Acorn, they mention Mach3 which has the same output as Acorn.

    Jim Dawson
    Sandy, Oregon, USA


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How do I determine how big of a power supply to use with my servo motors?

How do I determine how big of a power supply to use with my servo motors?

How do I determine how big of a power supply to use with my servo motors?