Bob Swinney -- Phase converters

Pete, if I understood Lloyd right, and I think that I heard the same thing a while ago from someone else, the BOSS controls really need all three phases to operate. And then from then on, all control circuitry is 220v or 110v based and thus you need extra relays and stuff just to operate the VFDs which usually use 10v for signaling.
Easy with a phase converter, hard with drives.
It may not be so simple because contactors may be interlocked with one another in a way that requires 110 or 220v. (something like, the spindle must be running in order to move table, etc)
What you say is possible, but what is also possible is that it will not work due to interlocking etc.
A good start can be found here.
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there is a power distribution schematic. It does not look very discouraging. But I would be leery of altering this mill.
Reply to
Ignoramus26200
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The axis drives are single phase.
As for control voltages, the VFD will accept a dry contact closure for run, and there is certainly a contactor controlling the spindle now that will readily provide that dry contact closure with 5 min of rewiring.
I didn't see a schematic, all I saw was a mediocre block diagram.
Give me a VFD of an appropriate size for the spindle motor, and a couple hours and I'd have the machine happily running on a 240V 1ph input.
Reply to
Pete C.
Per your chapter 4, the two transformers are single phase, so they can each be wired to the 240V single phase supply and their taps set appropriatly.
The three phas goes only to the spindle motor start/reversing contactor. contacts from the start/reversing contactor can be used for the VFD control, or better yet, those contactors are most likely driven by smaller relays in the control and the contacts of those relays would be a better choice to use.
Either way, a $200 VFD and a couple hours work. Very simple.
Where was Lloyd located anyway? I've got some comp time to blow...
Pete C.
Reply to
Pete C.
"Pete C." fired this volley in news:gl5kip$b33$1 @news.motzarella.org:
Nope. One AC supply runs off one 240V phase, a DC supply runs off a second 240V phase, and the motor runs off all three.
True, but I still have to rewire the main harness to get both internal supplies on one phase.
Unfortunately, it's also about four to eight times the cost for that VFD than what my RPC (locate OUTSIDE the shop, and thus "silent") would cost.
Oddly... even the folks who sell retro-fit kits for the R2E4, converting them entirely to new electronics, don't seem to want to mess with the spindle motor. They sell VFDs. They recommend an RPC for that machine. (?)
LLoyd
Reply to
Lloyd E. Sponenburgh
"Pete C." fired this volley in news:gl5p0g$rp0$1 @news.motzarella.org:
Ok... but my 3HP RPC cost me $63, all up, including a brand new motor.
And you still told us "rewiring". Well... If I have to re-wire the cabinet anyway, why not get the machine working per stock, first. THEN mess with it, if it seems reasonable. I don't have any particular love for the old technology, but it's a good foundation to thoroughly understand how the hardware, electronics, and firmware interact.
BTW... I'm in Northeast Central Florida. (it's even cold here for the next two days). If you've got a spare 2HP VFD and the time, "come on DOWN!" .
LLoyd
Reply to
Lloyd E. Sponenburgh
Yep, they are two seperate single phase transformers, they each connect to your 240V input. They were only connected to seperate phases on the three phase supply to better balance the load on the three phase and lower the amperage requirements.
That's just a few wires, 30 min of work.
The used VFDs I got from Iggy for $100ea would do it. New ones for a 2hp spindle are a couple hundred dollars.
Don't know, haven't seen their retrofit packages.
From Iggy's docs, there is nothing special about the spindle motor. The speed control setup is funky and probably not worth messing with, but that in no way precludes the use of a VFD set for simple 60hz output to power the spindle motor.
I spent some 5+ years doing CNC service BTW, however, the machines I worked on were generally newer. How far are you from Dallas anyway?
Reply to
Pete C.
The "rewiring" is barely more than the power connections. The power inputs to the two transformers and the VFD, the connection from the VFD to the spindle motor, and the three wires for the control connection to the VFD.
Yes, but I consider "mess with it" as retrofit for Mach3, not just rewire power and a VFD to get it running on single phase.
Actually, I do have a spare 3HP VFD on hand (got two from Iggy, one is on my Bridgeport now), and some comp time available. Got any good dive sites in the area? On second though scratch the dive thing, it's cold and I loaned my dry suit to someone in my dive club.
I could stick the spare VFD in the priority mail pretty easily...
Reply to
Pete C.
"Pete C." fired this volley in news:gl5qj1$fs9$1 @news.motzarella.org:
That, I really appreciate, Pete. Thanks. How much?
I might take you up on that, because my goal really IS to overhaul this beautiful hunk'o'metal into a modern machine. But right now, I have the RPC, it IS outside my machine room (out in the compressor shack), and it works fine. So, all I have to do is move around a couple of harness wires to get the two transformers on one phase, and I should be (hope!) cutting metal.
The machine was presumably "in service" when they unplugged it to load on my trailer.
However, as you maintained -- If I ran it off a VFD, it would at least be quieter and more efficient. It will get one sooner or later.
One question, please. How's the "spin up time" on a VFD-powered motor that's triggered externally like you recommend, vs. a motor running on an extant 3-phase supply switched by a contactor? I don't know what the BOSS controller expects, in terms of wait time for expected RPM.
LLoyd
Reply to
Lloyd E. Sponenburgh
I got it from Iggy for $100 and figured I'd keep a spare on hand or for future projects. I could send it to you to try out if you want.
If you already have the RPC up, you can certainly test the machine on it. The VFD is ultimitely where you want to go however.
Upgrading to a "modern machine" is certainly an involved project, but there are a lot of resources available these days.
I'm building up a small CNC plasma table based on Mach3 at the moment. I expect to have it completed in a month or two.
Yep. I believe Driveswarehouse.com is a decent source.
Spin up, spin down, dynamic braking, speeds, etc. are all programmable on a VFD. For your application you'd be looking at setting the VFD for 60hz output, and zero acceleration ramp (immediate full speed), and probably coast on stop to match the original performance since there is a brake in the machine.
Reply to
Pete C.
"Pete C." fired this volley in news:gl5s3e$tka$1 @news.motzarella.org:
Pete, if you can sit on that "test deal" for a few weeks, I'll probably take you up on it, and either return it or pay for it, as you choose after I'm done.
Right now, I'm busting out a 2-1/2" slab section, and re-forming for a 5" pour in and around where the new machine will sit. (one expenditure begets another... sigh...)
LLoyd
Reply to
Lloyd E. Sponenburgh
No problem, just delete the .DOH. to eamil me.
Reply to
Pete C.
How is the other one, working for you? Sounds like you are happy.
By the way I have more, some I can sell for cheap due to cosmetic damage.
I am very happy with a VFD on my mill.
I wish I could put one on my lathe, but this 40 year old motor that is 220v only, has bad insulation and leaks through insulation if powered by a VFD.
With a braking resistor, I programmed my mill to stop in 0.5 seconds with electric braking.
Reply to
Ignoramus26200
It's working very nicely. Having it mounted on the wall next to the Bridgeport works just fine. The only times I change speed I'm also changing tooling so reaching over and entering a new fewquency works fine. Otherwise with the original Brideport switch feeding the fwd/rev inputs it's just as easy as normal.
You should post what's available. Lloyd will be wanting one, probably other folks. Not sure if I need another at the moment since I don't have any more three phase machines.
In a lot of ways they're better than having real three phase power.
I bet a motor shop could re-varnish and bake that motor and get it in better shape. Adding a line reactor between it and the VFD might help. Or of course you could scroung a better motor.
I just set mine to 1 sec start and 1 sec stop. 1 sec is certainly faster than the stock coast to a stop.
Reply to
Pete C.
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Assuming that it is not like the Bridgeport Series 1 BOSS-3 through BOSS-6. Those have a *big* three phase transformer in the back power box, with each phase separately feeding a saturable reactor and a bridge rectifier and filter capacitors. These three supplies power the three large stepper motors. The power needed by these steppers is sufficient tha they felt that they needed to spread it out over the three phases. The actual computer and lower power driver circuits are all derived from a single phase as you describe below.
Later versions, starting with the BOSS-8 used servo motors, and were not nearly as power hungry, so they could be driven from single phase except for the spindle motor.
Unless it is an old stepper motor driven axis machine, in which case it may indeed be using the full three phases to power those electronics.
An imbalanced (voltage mode) RPC can fry the power transistors driving the stepper motors on this old design, so if you use a RPC, you need to take care to balance it beforehand -- at least with the BOSS-[3-6]).
Enjoy, DoN.
Reply to
DoN. Nichols
Ignoramus26200 fired this volley in news:-tOdnepKX7ax5OvUnZ2dnUVZ snipped-for-privacy@giganews.com:
powered
Not sinusoidal or modified sine-wave output from the VFD? What leaks, where?
40 years ago, they were using sophisticated varnishes on magnet wire. That's way later than the leaky old cotton or silk days. Of that, I know. I worked in the research and testing lab for Florida Transitron in 1968-69, before 'Nam slapped me out of the work-force for a couple of years.
(and to paraphrase someone you might know personally... Used 3-phase motors are a dime-a-dozen )
LLoyd
Reply to
Lloyd E. Sponenburgh
Iggy's docs indicate it is a servo driven system and that the power supplies are all single phase.
Reply to
Pete C.
"DoN. Nichols" fired this volley in news: snipped-for-privacy@Katana.d-and-d.com:
BOSS-9, Don. Pete was right in all respects, except that the two internal supplies do run off two phases. But they certainly can be made to run off one. The BOSS-9 R2E4 is all servo driven, and not power-hungry, at all.
LLoyd
Reply to
Lloyd E. Sponenburgh
[ ... ]
Probably from me -- and this only applies that I am sure of for the BOSS-3 through BOSS-6 machines. BOSS-8 had moved to servo motors instead of steppers, and are probably easier to run from single phase (except for the spindle motor, of course.)
Looking at the manual chapter which you posted a link to, this appears to be for the later ones, with a single power supply providing 128 VDC for all three axes from a single power supply -- thus it is probably running servo motors and servo amps (the "Motor Drive Module Assemblies"). This one will be easier to convert than the BOSS-[3-6] machines are.
The BOSS-[3-6] machines have a *big* three-phase transformer, providing lower voltage AC to each axis motor electronics from a different phase.
Each phase goes through a saturable reactor (mag-amp) and a bridge rectifier to a filter capacitor to provide power to the stepper driver for that axis. When stopped and stepping slowly, there is no current through the control winding of the mag-amp, so the voltage reaching the rectifier and filter capacitor is reduced to about 50V DC or less out of the filter. However, when stepping rapidly, a DC current is fed through the control winding, lowering the inductance greatly, and getting more of the AC through the bridge rectifier through to the filter capacitor (and the stepper drivers and motor). This produces an 80V power to the stepper motors to overcome the inductance of the stepper windings.
The stepper motor machines have big cooling fins on each stepper motor to deal with the heat from the current. The servo motors are just plain cylinders with brush caps sticking out.
At least on mine, the contactors are mechanically interlocked. Actuate one (with a short pulse of AC) and the other drops out before the first closes.
IIRC, the contactor coils run from 120 VAC (developed from a large step-down transformer which powers other things as well), and they are controlled by a 24 VCD coil relay plugged into an octal socket in the computer rack on the opposite side of the machine itself. (There are three boxes -- high power on the back, electronics on the right (as seen from the operator's position, and the interlocked reversing relay in another box on the side which also contains an outlet for a coolant pump, and another outlet for an operator's light.
If you are running the spindle motor from a VFD, you want to get rid of the interlock reversing relay, and give low-voltage commands to the VFD (easily derived from the relay which switches the reversing contactor.
I really should scan all of what I have for the older machines and send to you -- but too many of the pages are too large for me to scan reasonably, and I'm having problems getting the just acquired SGI computer (which comes with scanning software) to talk to the SCSI interfaced HP Color Scanjet 5c. (It is expecting a Scanjet IIc at best, I think.) The manual has gazillions of fold-out schematics too big for my scanner.
No reversing contactors should be between the VFD and the spindle motor. The VFD should receive commands to stop or to run forward or reverse -- at the 5V or 10V level.
It all depends on which version of the BOSS series he has. If it is BOSS-3 through BOSS-6, then things are more difficult. If it is a BOSS-8 or later, things are easier, and match your manuals. And your chapter 4 is a *lot* shorter than mine. :-)
Enjoy, DoN.
Reply to
DoN. Nichols
Lloyd, used three phease motors are a dome a dozen. I brought home two yesterday, one cost me $10 and another $15, both 2 HP.
What is not as easy to find is a 2 speed motor.
My alternative is to put a 5 HP inverter duty motor (which I have, also 184T) in the lathe, and rewire the starting lever to operate the drive instead. I am not in a hurry to do it, since the lathe works as of now. I postponed it until I would understand it condition a little better.
Reply to
Ignoramus26200
[ ... ]
Hmm ... I worked for the original Wakefield Transitron, and one in East Boston.
What ever happened to them over the years?
Enjoy, DoN.
Reply to
DoN. Nichols

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