[erikjgreen]

Hello, all -


I'm working on the re-wiring of my milling machine, and I've run into a question about power for the SD1525 servo controllers.

They're mounted in an open chassis with three controllers for X/Y/Z and one free slot. The chassis appears to have a power supply section integrated with it that includes four individual rectifying diodes and a capacitor.

My question, or maybe assertion, is this: It looks like I just need to supply an AC voltage capable of being rectified to within the allowed DC spec of the cards to the motor power supply terminals on the chassis in order to power the servos. Is this the case? I'm not talking about the card supply. I will be supplying the cards with 110v AC for their own power via a GFCI.

The original electronics were set up to supply the chassis with 83 volts AC, which if I'm correct about the power supply section in the SD chassis will get rectified into about 125 volts, which is the rated DC for the motor.

According to what I've read on these cards, they can accept a wide range of DC voltage input (in this case supplied by the rectifier section of their own chassis) depending on the desired voltage for the servo motors.

Can anyone with experience with this Servo Dynamics chassis (used in Lagunmatic, Tree, and other mills) verify this?

I want to be sure I can just hook up 83 volts to the chassis input (it was this way before) and have the chassis supply valid DC power to the cards.

I also want to know if I need to replace the servos with a higher voltage model if I can just up the AC current to the chassis (within the range of allowed spec of the ripple cap, of course) and get a higher DC voltage range sent to the servos.

I'm thinking this is the case because these cards were designed to work with a large variety of servo motors, but I want confirmation before I blow something up

Thanks,
Erik

[erikjgreen]

I think I may have answered my own question.

The power supply in the chassis appears to be a Servo Dynamics 4017pm "DynaPower".

If my unit matches the manual like I think it does, it accepts power input between 45 to 120 volts AC single phase and supplies up to 6 servo amps with power. DC voltage is 1.4 times the AC input voltage.

http://www.servodynamics.com/Manuals/4017pm_manual.pdf

It looks like from the wiring in my mill that 110v was still being supplied to the servo chassis for some reason, so I'll look into why that was. Apparently this power supply gives the drives all they need from the AC input voltage alone.

I'm thinking I'll re-wire the transformer to supply power to this chassis, and use a 220v feed to power the PC "brain" of my mill, with 24v for some other functions like contactors. The only thing remaining three phase will be the spindle motor, which I'd like to put on a VFD.

Any further info on this power setup or confirmation of my assumptions above is welcome.

Erik

[Al_The_Man]

It would appear that is a switching supply. If you have this,why do you need anything else?
What voltage are the motors rated for?
Al.

[erikjgreen]

125 volts DC. They're Baldor "Big MHO" DC servos:

> Baldor Big Mho Permanent Magnet Motor
> Model # 4201990
> 500 oz-in
> 120 VDC 2500 RPM
> 10 AMPs Constant, 39 AMPs Peak
> Tach output 7.0 V/KRPM
> Volt Constant Kc=40 V/KRPM
> Transducer = Encoder 1000L

I suspect I need little else for power in the cabinet, except for things like the coolant pump, possibly a chip conveyor if I want to build one, and of course the spindle and the control PC (which I think will be 12 volts running from a wall wart). To clarify what I said above, I meant I'll run 220v single phase to the mill instead of three phase from the converter like it is now. That 220v will power the 83 volt transformer, 110v for the wall wart and coolant pump, and possibly a 24v control transformer to run contactors and anything else I can think of.

The wiring in the original layout had the secondary of a transformer set up to provide 110vac connected to one set of the posts on the chassis in addition to the 83 volt main supply. I don't have the wiring manual for this mill, but the diagrams from the next model up from the same year have the same thing in them (check my mill thread for a zip file containing those if you like.)

I'm going to check the manual I found against the PS unit when I get home to see if it matches and if I can figure out what the extra wires were for.

Erik

[erikjgreen]

Well, no luck.

I peered beyond the wires and got my knees dirty, and found out that it's not a packaged card type supply in a slot. Also, what I thought were diodes on the power supply chassis were in fact either diodes or power transistors on one of the sd1525 cards (duplicated on all of them).

I identified the AC (I think) supply to the chassis (which has the model number in the thread title), the lines to the servos (still connected) the shielded line to the tach, and I have an idea what many of the color codes in the wire harness are for. Still not sure what the extra 110v lines are for, I re-checked the wiring diagram from the Lagun 310 cnc mill I have (mine is a cnc 250) to verify they were there, too. There appears to be a small transformer in the chassis power supply behind the big capacitor, so it's possible the 110 is getting changed to something else there, maybe to power the encoders or limit switches? The encoders are connected directly to the dynapath controller.

The 110 transformer was there in the box to power the contactors/starters for the spindle and the coolant pump.

I dug out a couple pics from my mill thread. Here's the overall electronics layout before I disassembled it:

http://i280.photobucket.com/albums/k...l/P6200178.jpg

and here's a closer pic of the servo drive chassis.

http://i280.photobucket.com/albums/k...l/P8170006.jpg

In case anyone has worked on one of these before. I know the lagun CNC 250 used them, and the CNC 310 may have. I've also seen people discuss them being on tree mills and some bridgeports. These are all mills from the 1988-1990 time frame.


Should I try applying the 83v AC power to the terminals on the chassis it was connected to, and see if that powers it up?


Erik

[Al_The_Man]

It seems that the large electrolytic is in the DC supply to the drives, there should be a bridge rectifier and behind that a large transformer?
Al.

[erikjgreen]

I don't see another transformer, just the little one there.

I did read the drive manual again. It seems each drive has its own built in shunt regulated power supply section, so each one accepts 45-120vac input and sends DC to the drive at 1.4x the voltage of the AC. Interesting design, considering how often power supply components fail.

Here's the manual I'm looking at for the drive, it's the closest I've been able to find to the open cards in slots I have:

http://www.servodynamics.com/Manuals/1525brs_manual.pdf

The thing now is that if the cards take AC, what's the big cap for? Still used for filtering on the AC legs?

It looks like there's another power supply section in the chassis, for something other than the drives. Either that, or one person suggested it may be a board for damping the braking surge from the servos when decelerating... not sure how that would work with a card instead of just a resistor.

Erik

[Al_The_Man]

That manual appears to be a self contained drive, the ones you show look like the typical separate supply type, an electrolytic cannot be used on AC unless bi-polar.
There appears to be a red and black going to something other than the drives, normally this would be to the bridge, can you trace this and see where it is hooked into?
Al.

[erikjgreen]

Will do.

That manual is the closest I've been able to find on the net. My drives are SD1525-10, and they have the same test points and (I've been told) calibration procedure as that manual.

I'd love to have a manual for this particular chassis and drive, just can't find one...

Erik

[mike_Kilroy]

think u just clicked on wrong link for ur drive manual... yes, BRS is same drive as BR model, but includes ac (S)upply. if u ant better manual on YOUR drive, get it here:

Servo Dynamics - Brush Analog Amplifiers

and pick BR model instead.... IIRC back in ur post u had a 1525br-10 (10 amp) -xx where xx is simply something smal special in it. if u need to know what that small special thing is, phone them; vivian will be happy i think to tell u what is special.

[erikjgreen]

I had looked through that manual before. It doesn't have the PS section on the BR drive, but the other one (BRS) had the test points exposed and seemed like a better match when I was looking for the calibration procedure.

The truth is, neither of them are correct. I need a manual for this particular chassis, model SD4-1525-10-3-10.

I may give you a call, although at my day job I'm limited in ability to make personal phone calls (less so in web posting, fortunately

I traced some wires in the PS last night. I was able to get most of that done without removing the chassis from the cabinet, although I may do that this weekend.

I found out one explanation for the 110v power wires coming in... the two fans cooling the chassis run on 110... obvious in hindsight.

I also discovered a bridge rectifier hidden under the big cap, using the metal chassis as a heat sink. I think I can safely conclude that the rectifier and big cap are the main components of the DC power supply for the servo voltage.

I'm still not sure what the little add-on board there is for, working that out. From the wiring it seems connected to the DC side of the servo power supply, and there is a small transformer on board, along with a resistor mounted separate from the board (to dissipate heat?). The small board is connected with three wires to each servo card via connector J4.

At this point I'm thinking I'll need to connect both 110vac and 83 vac power to the chassis to get the drives running. Since I'm going to install a 10 hp hitachi VFD on this thing (oversized for derating) I'll be installing 6 gauge wiring to the cabinet in the next week or so.

Once that's there I'll proceed to wire the fuse/disconnect block to the transformers, then those to the servo chassis, at which point I should be ready to try putting a small voltage on the input wires to the drives to see if the servos move (they worked ok with the dynapath controller, so they should).

More info from wire tracing as I get it. Again, if anyone has a manual for a mill that uses this chassis with a wiring diagram or a manual for the chassis itself, it'd be much appreciated. Thanks to the wire tracing last night I've got all the incoming wires sorted into bundles for limit switches, tachs, encoders, power, and servo wires. I have some work to do tracing the coolant pump lines and the lube level sensors (at least that's what I think they are) but mostly I'm ready to start wiring up the new components.

I'll copy some of this info to my build thread for the mill in an update later.


Erik

[mike_Kilroy]

guess u got some special stuff there. sounds like the one to call is the factory:

(818) 700-8600 I said vivian, meant Lillian who answers the phone; if you say I suggested u call, she may help more (or it may have the opposite effect! u decide)

anyway, it sounds like only they will be able to help you out with details u want. we simply use their stuff on occassion so know little more than u at this point.

good luck!

[Al_The_Man]

I also discovered a bridge rectifier hidden under the big cap, using the metal chassis as a heat sink. I think I can safely conclude that the rectifier and big cap are the main components of the DC power supply for the servo voltage.
Erik

What feeds the bridge and does it look like a ~50-60amp component?
Either it would have had a large transformer feeding it or it was fed off of the incoming power direct?
Al.

[erikjgreen]

It's fed off of the 83 VAC output from the giant transformer at the top of the mill cabinet enclosure.

From what I can see, nothing else feeds off that transformer, so that's its only purpose.

Erik

[Al_The_Man]

So that solves that mystery!
So Re-reading your previous posts then, is your intention to fit larger servo's or up the power supply to the rated voltage of the existing motors??
Running the existing motors at less than their rated voltage just means they will not attain max rated rpm.
Al.

[erikjgreen]

Right now, I'm going to go with everything as-is, assuming it all works.

Once I get the electronics for the mill done (I'm installing a Mesa based control set-up) and all the accessories working (coolant, lube sensors, chip control, spindle encoder) I'll evaluate. I might tweak the voltage a bit with the existing servos, if I'd like more performance. That'd require either rewinding the transformer or replacing it, unless I wanted to go with 154 volts DC based on 110 AC... too much for these servos.

I'm thinking if I need to replace one of them due to failure I'll switch to an AC type, but it depends on what I could get replacement DC servos for. They're hard to find in this size (500 oz-in), I've only run across one locally for a decent price. Plenty of AC units though, some with matching drives.

Onward and upward I guess.

Erik

[Al_The_Man]

Common misconception that the power supply has to be at the motor rated voltage, there is no direct line between supply and motor, there is a drive in between, the minimum supply voltage for max motor performance is recommended to be +10% of motor rated.
Power-Supply Considerations For Servo Amplifiers
The maximum rpm can usually be either limited at the drive or the controller.
The one proviso of using mains voltage is that the DC cannot be referenced at earth ground.
Al.

[erikjgreen]

It's worth considering since I've got the overhead in the servo amps (apparently, considering I don't have the right manual) to try it. I'd be reluctant to try it at the moment without having the manual for this particular amp card though.

I know the mill runs the servos well enough to work using the existing voltage, and I'd want to try using it that way before I add more variables to the mix, too.

Good article, I'll have to read it through again and compare values to my set up, especially if I can get the right manual. A rough estimate for the power my motors need seems to indicate I'd need to feed it AC somewhere around 110V or so, but I'd have to be careful to measure the actual voltage after each stage so I don't smoke anything, especially since I don't see anything yet that will let me limit the max voltage on this model amp.

I'm still inclined to go with "if it ain't broke, don't fix it" for now, but I'll give it some thought...

Erik