ProtoTrak - Why 3 phase and 110V to the same machine?

So I'm reconnecting my little ProtoTrak bed mill, and looking at the label on the electrical box that says "Caution, disconnect Both 110v and 220/440V power before working on this machine". I find myself wondering why this is the only machine I have that is wired like this. We like to move this around the shop as needed and if there was only one connection it would be less work to drop a single line and not have to snake an extension cord to the machine each time, plus that would leave one less cord to clean up around and/or get damaged. I've even been tempted to put a small transformer in the box to make 110, there's plenty of room. The control won't start with only 110 connected, it needs both or the monitor stays dark.

Most machines I have have control transformers to make 110, some only have one to supply an outlet for a trouble light or other tools for a tech. I'm not certain this even meets all NEC rules.

Anyone here know a good reason for this?

And yes I did ask Southwestern once upon a time and got the answer - "It won't run if you don't connect both wires". Duh.

No "good" reason other than the company is too cheap to install a control transformer inside the cabinet. You could tho...

Mud said:

Anyone here know a good reason for this?

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I can't necessarily call it a 'good' reason, but..

Lots of stuff is wired 'delta' feed on 3-P. No neutral carried to the machine. Or was at one time.

Not really a show-stopper if your control transformer is 240 leg-to-leg primary, 120 secondary, but it also needs its own fuse or breaker, 'coz for-sure wotever is protecting the heavy goods won't trip whilst frying the small s**t.

A "Global" maker might have just NOT wanted to try and anticipate what local codes or conditions called for, where the disconnect might be relative to where the control Xfrmr was, whether the feed was 240, 480, or.... simply copped-out and said run a separate 120.

A more diligent outfit took care of that for THEIR customers.

It ain't hard to change, just as you figured.

I surely would do.

I even keep a few tiny MIL-gen-set / aircraft / marine low-amperage breakers around so I don't have to dig through drawers of glass cat'ridge fuses.

Doesn't bother me a bit. In fact I like it because in my home shop I can program and test run a profile without firing up the somewhat noisy, power hungry phase converter.

I don't know if it is the reason or not but I agree with Pix Man, in the smaller shop without proper 3 phase it can be a bonus ,I ran mine of a generator for years and it meant that I could do program and setup before stating the genny.

I do wonder how they get away with it though as I thought having two supplies into the same electrical cabinet would violate code.

PixMan said:

Doesn't bother me a bit. In fact I like it because in my home shop I can program and test run a profile without firing up the somewhat noisy, power hungry phase converter.

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Eurotherm/Parker SSD DC drives are easier yet, as they can be set-up off the test strip with the pass-elements shut off.

Downside didn't click until y'all brought this thread up though.

I DID have my Armature and Field SSD's running their control sections directly off mains 120, one side of the 1-P 240 to N.

And then... blew the brains out of a costly 514C 16A unit when I fat-fingered the Fluke's nekkid probes across 6A of dirt-cheap SSD 507 output. "Fast" fuses aren't.

IF I had been running each of those off separate isolation / control transformers for my 120 VAC, there is a better than even chance that particular pass-element spike wuddna' blown the other drive, transformers being low-pass, not fast-mover, 'chokes' inherently as well as transformers.

Not up for more destructive testing, but they are cheap enough, so may just add those plus a Varistor and tiny capacitor 'on principle' to give those allegedly 'fast' fuses the time they actually need to react.

They just cheaped out. Our Servo 5000 requires 240 3 ph for the spindle, 240 single ph for the servo drives and 120 single ph for the controls! I added 2 - 3 pole contactors and an E-stop to shut it all off at once

garyhlucas said:

I added 2 - 3 pole contactors and an E-stop to shut it all off at once

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Not new.

American automakers invented that sort of s**t.

THEY saved ten bucks, order qty of 100,000 a go, on each of two million units.

WE have to spend a hundred bucks sorting what is needed and where to find it, then buying as onesies and installing to make up for the 'savings' the bug-f*****rs banked as bonuses.

Well not JUST "American". '72 BMW Bavaria had a 110 US$ surcharge for 'Skai' AKA "MB Tex" in another part of Germany artificial leather upholstery. Asked what real leather cost. $750 extra. How about cooler in summertime fabric? That was extra also.

Ok - so what if you just take the standard, NO extra cost upholstery?

Uh.. there is no such option. You have to pay extra for one of those three, and nooo we will not ship a BMW without seats, either..

garyhlucas said:

....Our Servo 5000 requires 240 3 ph for the spindle,

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Don't know what make or HP that spindle drive is, but many <7.5 peak HP 3 phase drives will work fine on 240 single phase. Since you've already got it all set up it's not worth changing, but for future planning it's worth a look at.

I'm running my Mori Seiki on 240 single phase to the control, servos and spindle for over 3 years now. Added a small inverter to drive the coolant pump as that was cheaper than getting a single phase coolant pump.

My old Shizuoka and Bandit had 3-ph for the machine and 1ph for the control. The control plugged into the wall separately from the machine.

Looking at mine and was thinking it is possible to use a VFD to control spindle speed without affecting the rest of the machine.. no?

Not a ProtoTrak but, my mill with its analog drives and Fagor control needs only three phase for the spindle. The control and drives are 110V. It was wired at the factory with two lines also. One for the three phase and one for the 110V. I can run the control and servos without the spindle power on though.

Bill

Did the prototrak retrofit kits come before or after they produced a full machine?

If the retrofits came first, I would assume they are just selling a mill they retrofitted in house and sell as RTR