More updates on the Bridgeport conversion project

Great!

Hmm ... perhaps not quite close enough for the old stepper axis BOSS-3 through BOSS-6 machines -- there was very little safety margin with the maximum voltage of the stepper driver transistors when the saturable reactors (mag amps) were calling for maximum voltage for fast step rates -- but probably good enough for what you have.

Hmm ... let me try a couple of ASCII drawings to see which it is closer to (the usual advice for Courier or another fixed pitch font applies. I know that you know to use it, but in case someone else is reading this it may help them)

Three phase transformer. Three windings on separate arms with figure-8 core.

+------------------------------------------------------------+ | | | +---------------------+ +-----------------------+ | +---| |---+ +---| |---+ +---| |---+ | W | | P | | W | | P | | W | | P | | i | | h | | i | | h | | i | | h | | n | | a | | n | | a | | n | | a | | d | | s | | d | | s | | d | | s | | i | | e | | i | | e | | i | | e | | n | | | | n | | | | n | | | | g | | 1 | | g | | 2 | | g | | 3 | +---| |---+ +---| |---+ +---| |---+ | +---------------------+ +-----------------------+ | | | +------------------------------------------------------------+

Sola style ferro-resonant "constant voltage" transformer. Single phase with large AC Capacitor

+------------------------------------------------------------+ | | | +---------------------+ +-----------------------+ | +---| |---+ | | +---| |---+ | W | | P | | | | W | | S | | i | | r | | | | i | | e | | n | | i | | | | n | | c | | d | | m | | | | d | | o | | i | | a | | | | i | | n | | n | | r | | | | n | | d | | g | | y | | | | g | | a | | | | | | | | | | r | | | | | +----+ Gap | | | y | +---| |---+ +----+ +---| |---+ | +---------------------+ +-----------------------+ | | | +------------------------------------------------------------+

Both have a lot more winding and a lot less open window than I showed, but I made it this open to make it clear how it is set up. The ferro-resonant has another winding (on the primary side IIRC) which is connected to an oil-filled AC capacitor and nothing else.

Any photos?

Hmm ... any useful markings on the drivers? Terminal strips marked for function? Trimmer pots used for zeroing balance and tuning gain for both input and feedback and for adjusting damping.

O.K. That voltage is probably necessary to get full torque at full speed from the servo motors you have. (There should be maximum voltage and maximum current on the motor's labels.)

You can run them on lower voltages, but as a result you will get less maximum speed and less torque.

Those could be for inhibiting motion on the two directions, a common, and a separate inhibit for each direction.

Is there any documentation on them in the Bridgeport manuals which you have? At least on the function of the wires and where the trimpots are for different functions? If so, I would suggest trying to use them first -- since they are a proper match for the supply voltages needed for the motors. Not sure whether your AMC drives are for that high a voltage.

What about those unidentified three wires?

If all else fails, the drives should have current limit on the output to prevent partially demagnetizing the permanent magnet fields in the motors, so you *could* use a contactor to short the output to the motor armature on each one -- or in series to prevent current from reaching the motor. But I'll bet that those three puzzling wires are the inhibit functions.

O.K. And to make sure whether or not what you have is actually a three-phase transformer.

Good Luck, DoN.

well, hopefully it would be OK here.

IIRC mine looks different.

.-------+-------. | oooo|oooo | | oooo|oooo | | oooo|oooo | | oooo|oooo | | oooo|oooo | .-------+-------.

The picture is on the bottom left here:

and it confirms what I am saying.

This one, seems to be one phase transformer.

Hard to see without removing them, I will try.

Yep, max voltage 145 volts, pulse amps 32. (wow)

See

I will check, I think that they are for power. I can find it out by tracing wires.

I do not think so.

Not even close, 80v as opposed to 145.

I should try to make them identified.

i

Hey Iggy,

The following is something that I just wrote to someone else, about a CNC lathe I bought a bunch of years back. It might do you well to think about it relative to what you are doing. My rotary phase converter was pretty good at voltage balances too, but it didn't "help"!!

===================================== While I lived in Windsor, Ontario, I had most of my shop at a good friend's tool & die shop in an adjoining but empty building he had purchased for future expansion, so room was abundant (10,000 square feet !!) and I had all the power supplies I wanted (3 phase for

110-220-440-575-600). Way back when I got it, the lathe took no end of screwing around to get it to run. Once I got it to operate at all, it worked OK as little as I tried it from the touchpad on the controller, but would NOT accept an off-line program!!! For me it's just a hobby of course, so I wasn't in too much of a rush, just very pleased it did run. And the only thing I "programmed" was very simple turning and a bit of thread-cutting and doing tapers. Lots of fun. Then 9 years ago I retired and moved to a small town, just a village really.

But when I moved, I found that no 3 phase at any voltage was available at a reasonable cost. I did luck out on the fact that the lathe is

220 three phase, so I made a rotary phase converter. The convert or runs great and powers two other lathes, my Bridgeport, and my surface grinder, just fine. But when I applied it to the CNC lathe, KAPOW !!

I should have looked more closely at how the power is distributed at the lathe. Turns out the ONLY thing on that lathe that runs "three phase" is the spindle motor!!!!!!!! All the other requirements are just single phase, using different ones of the phases to "balance" the power applied, so I should at least have hooked all those across the "hot phase". And that is where it sits today. I intend to get at it, but retirement makes me even busier, so I just have not taken the time.

======================================================

So, something to consider Iggy, before you hook up the RPC !! Look very closely at the electrical drawings!!!!!!!

Take care. Have fun.

Brian Lawson, Bothwell, Ontario. 'xxxxxxxxxxxxxxxxxxxxxxxxxxx

Brian, thanks for the warning. I already hooked it up to the converter, so if there was any damage, it may have already occurred. I think that I was lucky and voltage from lines L1-L2 was applied to the transformer and such.

i

Okay, I think you got it. Two phases are attached to the generated leg. You do not want the control power transformer on those. Stick to the line connected leg.

Wes

do not want

Exactly. I traced some wires last night, it does look like the servo stuff is using lines L1-L2 and L3 goes to the spindle motor only.

In my 3 phase wiring, I made really sure that L1-L2 are where they belong.

i

do not want

Excellent. I hope your son is by your side during this, subject to the attention span of small boys. Watching is part of learning, especially if your son asks good questions and you are willing to stop and explain.

Obviously he can't advise you but when he makes connections using your explanations of what you are doing or trying to understand, a bit of praise for getting a grip on it or asking the right follow up questions is positive reinforcement to encourage a life of learning.

I have a strong feeling you are a dad he wants to emulate.

Wes

-- "Additionally as a security officer, I carry a gun to protect government officials but my life isn't worth protecting at home in their eyes." Dick Anthony Heller

I think the servos you bought are 80 volt. You may (probably) be fine if you go the AMC route.

I'd suggest your son do a speed and acceleration test to help you decide. this would be fun. Take a 2:1 transformer, a bridge rectifier, and a electrolytic cap if you have it. Show him how this makes AC into DC. Have him read a web site on design of these. (Today's reading English lesson) Now hook it to your X axis with the table at center travel. Bump your power to it for a second and measure acceleration and velocity. if your transformer has 4:1 reduction, do that one too. If you need more speed, make a run with

110 to the rectifier. Extra credit, use a variac in the circuit.

If you make a point of doing these lab exercises at every opportunity, you'll have a friend for life.

Now, decide if 80 volt is enough. If it isn't and you want to go the AMC route, there are several amps that will work. they tend to go in the $50-$80 range.

Karl

Karl, I do not really need to set speed records on this mill. Since it is not enclosed, the faster it goes, the more dangerous it is to any living being who would be unlucky enough to be close to it. (many obvious safety warnings apply etc)

I figured out some servo wiring (see my more recent post) and ran the Y axis servo motor. I checked out the speed at 30 volts with a little power supply I had. I think that it was almost adequate. So 80 volts is not a problem.

The question that is on my mind right now, is that perhaps I should simply keep everything that is in the cabinet -- all the safety wiring, relays, etc, with new encoders, and hook up EMC/PPMC to that just as Heidenhain was. The plus is I keep all the safety features that seem to be provided by all those relays.

Of course, I could only do it if I figure out the basics of their wiring.

I would suggest you rip it out if you plan to keep the machine long term. Stuff breaks at the least opportune times. Keeping obsolete equipment is just asking for future trouble. Just my 2 cents.

Karl

Karl, would you say the same thing about all those safety relays and such? Just rip out everything and redo everything? Or just the amps?

I am sorry for being a little redundant. I want to make sure that I do not do anything rash and stupid.

i

If you don't want to do anything stupid, then don't do anything at all!

I'm an empty box guy. Rip it all out. Inspect components to see if you want to re use. Wire number all the wires going out to sensors and devices. Keep a spread sheet of wire number and function (way quicker that doing a EE drawing) All wires go between two devices, so I keep device 1, pin#, device

2, pin#, wire number, color, voltage, function on each line. All my 24 volt dc is blue, my 5 volt red, my 10 volt orange, common white. I keep all the AC completely separate and use red, yellow, back for hot, white common, green ground.

Start building your machine and maintain that spreadsheet. When I'm done the machine is duck easy for future maintenance. And, The time I waste by putting the same components back in is more than saved with good docs and a better layout in the cabinet.

Karl

[ ... ]

O.K. Standard single phase transformer. Probably most of those taps are to allow it to be configured for different line voltage inputs

-- probably 240 V up to well over 480V -- 5??V perhaps

And it may feed that voltage from a single phase to all of the electronics in that rack. I note that each servo amplifier appears to be fed by its own transformer (above it) which otherwise do not have enough terminals to allow line voltage tweaking here. So it looks as though your entire three axes are run from a single phase -- making it easier to re-wire to use that in place of the original three phase.

Single phase for sure.

Yes. Nothing special. I'm not even sure why you commented on the shape -- it is a standard transformer core. I was expecting something different.

Single phase.

It looks as though each servo amp has its own small transformer on the board -- probably to isolate the on-board circuits from the controlled voltage and current.

No photos of the servo amp boards from an angle which will show much of the components -- I can't even tell whether there are trimpots within reach of the front edge.

The board on the door (or side wall?) appears to be the serial interface board -- which is likely to be set up to support either RS-232 or 20mA current loop.

Yep -- the servo amp must be tuned to never exceed that 32A limit. You have 9.5 V/1000 RPM and 2500 RPM max, so a maximum of 27.75 V from the tach at max speed.

O.K. Please do so. :-) If they are power, they probably go to the transformers mounted just above them.

[ ... ]

So -- the question is whether you can sacrifice the maximum speed and torque combination for your uses.

I'll look forward to that.

Good Luck, DoN.

[ ... ]

Consider that a certain percentage of CNC milling is rapid moves

-- moving to cut on another edge, or moving clear to change the tool -- and here is where the maximum speed helps you most. Seldom are cuts actually made at those speeds. (And the rapid moves are also where servos are a major win over steppers. :-)

One thing worth doing at the same time (or at last once you are setting up the servo amps if you use other than what is already tuned for it) is to hook an oscilloscope to the tach output voltage, then feed a low frequency square wave (perhaps 10 Hz or so) into the command input to the servo amp (make sure that the square wave goes equally above and below ground so it will move back and forth around a center point instead of driving to one end and hitting the stop), and look for proper damping of the tach output. If it overshoots, you will likely have hunting with physical overshoot and motion back. If it moves up with a very rounded leading edge, then your motor will lag far behind the commanded position. With just the right amount of damping, it will be a fairly vertical leading edge, a tiny amount of rounding at the corner and then a flat top. (Very much like tuning an oscilloscope probe to the input capacitance of the scope using the 1 KHz square wave.)

This tuning should be with the motor driving the table, and a typical load on the table -- milling vise and something on the large side of what fits in the vise -- and compare the change when you empty the vise -- and when you remove the vise and work with a bare table (sort of like a single plate of aluminum held down with workpiece clamping sets. :-)

The servo amps which I have include places to plug in extra capacitors to tune the damping close, and trimpots to fine tune it. (They also have a built-in transformer and power supply to run from 120 VAC.

O.K. Saving the image of the transformer then zooming in on a servo amp shows two gray multi-turn trimpots visible. There really should be more -- I guess accessed via the top or bottom edge instead of the front edge.

Enjoy, DoN.

Sounds a little high, 380 V into a rectifier-filter will give ~ 537 V DC. I suppose if this is a center-tapped winding, then they could get 270 V, which sounds more reasonable.

It is very common for the end limit switches to be fed to the servo amp, to disable the amp to drive toward a tripped limit switch. This could take 3 wires (common or + 15 V, and the two limit switch contacts). These would often be set up for an NC switch, so a dirty contact ot broken wire would disable the amp in a fail-safe manner. Then, there's the velocity command signal, two wires.

Just make sure you have some system to E-stop the drives. Either inhibit them or kill the power input with a relay. The limit switch => inhibit likely runs through some part of the CNC control, which you have pulled out.

Jon