[Parkgrr]

Hi All. In the middle of rehabbing a Multicam 6x12 and feeling frustrated about just how many voltage numbers I am seeing both in my cabinet, device manuals, and in online resources as I piece things together. Can someone take me to school? My spindle is rated at 220 Delta, my spindle VFD and servo drives want 208-230, my CNC cabinet has a big fat 208v badge on it and people tell me the whole system can run on 240 delta. I know that the only actual 3 phase US power standard in the ballpark is either 120/208Y or 120/240D (this is all the while I'm seeing people talk about "220" and "110" which I know doesn't exist). I’m so confused.

What gives? Why such an enormous breadth of numbers when it comes to electronics standards? It seems to me that anything that is taking all 3 phase lines (not just one line-neutral) can either take power from a 120/208Y service OR a 120/240D service as most of these internal devices seem to be rated at 230, which is in the 10%+/- allowance of 240v AND 208v.

I recognize the differences between Wye and Delta and the benefits of each as a building supply, however I'm not seeing a difference as far as giving a 3 phase 3 line input beast some juice.

Not looking for opinions, gripes, or what has worked for you by chance. I also recognize there is some ancient history playing into these numbers which I'm not interested in. The biggest goal is to run a machine in the way it's happy with, and not fry anything when it's connected to power for the first time. Guh. Thanks folks.

[Jim Dawson]

For the most part today there are 200V class and 400V class devices. The 200V class devices are perfectly happy running between 180V and 250V, and the 400V class devices are happy between 380V and 500V. Either will run on 50 or 60 Hz.

The 3 phase waveform looks the same whether it comes from a delta or Y connection. Only the neutral relationship changes between the two, so if your machine does not use the neutral then either is fine, and most machines do not use the neutral.

On older equipment it is common to have multiple tap control transformers for the machine control power, this allows you to adjust the control voltage as needed to bring it into the operating range of the connected devices. Some of the older equipment also had multi-tap main power transformers to allow the same adjustment.

Your machine will run just fine on 208 or 240 3 phase, and most likely will also run on 240 single phase depending on how it is wired and what VFD you have. I have seen some Multicam machines that had a connection diagram for both 3 phase and single phase in the cabinet near the disconnect switch.

[Parkgrr]

Hi Jim thanks very much for such a simple answer. It makes a lot of sense and seems to round up all of these different philosophies I've been hearing. My multicam indeed has a single phase transformer to pare down voltage for the control circuit, this was confusing to me because the machine has (multiple) huge 208V badges, which made me imagine that I had to get 208v right on the nose to not risk wrecking something, so why have a transformer with multiple input tap options? Makes much more sense knowing that while these 5v and 12v boards won't be happy with a broad voltage range, the 208/230/240v rated components will, thus a control circuit transformer.

The machine runs a Yaskawa GPD 515 G5 VFD to operate the 16hp spindle, however you're right that there is an alternate wiring diagram on the machine that indicates how to apply single phase with two lines. Going to get on the phone with Yaskawa today to see if that VFD could somehow take single phase as if the VFD can I already know the rest of the machine can as well. I'm still a little lost as to why multicam was so specific on that 208v number on the cabinet and doesn't state that it can do 208 or 240.... Their documentation leaves a lot to be desired.

A question, what do you mean by a machine that doesn't use the neutral? Is that to say that the machine doesn't receive the neutral in any way or that the machine doesn't use the neutral to ground out for it's operation (or something similar)?

[mactec54]

Hi Jim thanks very much for such a simple answer. It makes a lot of sense and seems to round up all of these different philosophies I've been hearing. My multicam indeed has a single phase transformer to pare down voltage for the control circuit, this was confusing to me because the machine has (multiple) huge 208V badges, which made me imagine that I had to get 208v right on the nose to not risk wrecking something, so why have a transformer with multiple input tap options? Makes much more sense knowing that while these 5v and 12v boards won't be happy with a broad voltage range, the 208/230/240v rated components will, thus a control circuit transformer.

The machine runs a Yaskawa GPD 515 G5 VFD to operate the 16hp spindle, however you're right that there is an alternate wiring diagram on the machine that indicates how to apply single phase with two lines. Going to get on the phone with Yaskawa today to see if that VFD could somehow take single phase as if the VFD can I already know the rest of the machine can as well. I'm still a little lost as to why multicam was so specific on that 208v number on the cabinet and doesn't state that it can do 208 or 240.... Their documentation leaves a lot to be desired.

A question, what do you mean by a machine that doesn't use the neutral? Is that to say that the machine doesn't receive the neutral in any way or that the machine doesn't use the neutral to ground out for it's operation (or something similar)?

16Hp is to much to run on single phase 240v so stick to the 3ph supply the VFD could run on single phase but not for a 16Hp spindle motor 7.5Hp is about the limit for single phase use

[Al_The_Man]

I'm still a little lost as to why multicam was so specific on that 208v number on the cabinet and doesn't state that it can do 208 or 240.... Their documentation leaves a lot to be desired.

A question, what do you mean by a machine that doesn't use the neutral? Is that to say that the machine doesn't receive the neutral in any way or that the machine doesn't use the neutral to ground out for it's operation (or something similar)?

In N.A. the typical use of a 208 3ph star transformer is for industrial lighting circuitry, as it produces 3x 120v 1ph from each phase to star neutral.
Odd that it is quoted for a 3ph industrial machine?
All the industrial machines I have worked on have generally specified ±10% supply tolerance.
Al.

[Jim Dawson]

Hi Jim thanks very much for such a simple answer. It makes a lot of sense and seems to round up all of these different philosophies I've been hearing. My multicam indeed has a single phase transformer to pare down voltage for the control circuit, this was confusing to me because the machine has (multiple) huge 208V badges, which made me imagine that I had to get 208v right on the nose to not risk wrecking something, so why have a transformer with multiple input tap options?

My pleasure. The multi-tap options allow the machine to use a range of input voltages and allow adjustment to match the devices, most notably for the older style power supplies.

Makes much more sense knowing that while these 5v and 12v boards won't be happy with a broad voltage range, the 208/230/240v rated components will, thus a control circuit transformer.

Modern DC power supplies normally accept a wide range of voltages, 80V to 250V. The older ones require the input voltage listed on the data tag, normally 120V or 240V +/- 10%. Universal input power supplies were not available before the late 90's or maybe a bit later, not exactly sure when they were in common use.

The machine runs a Yaskawa GPD 515 G5 VFD to operate the 16hp spindle, however you're right that there is an alternate wiring diagram on the machine that indicates how to apply single phase with two lines. Going to get on the phone with Yaskawa today to see if that VFD could somehow take single phase as if the VFD can I already know the rest of the machine can as well. I'm still a little lost as to why multicam was so specific on that 208v number on the cabinet and doesn't state that it can do 208 or 240.... Their documentation leaves a lot to be desired.

I have to agree with Mactec54 here, 16HP would be way too much to run on single phase. I'm pretty sure that Multicam offered spindles as small as about 7.5 HP on that machine and those could be run on single phase. I suspect the the 208 badges would be to warn the installer that the machine transformers are tapped for 208V input. An interesting side note is that my Haas (7.5hp spindle) is rated at 208V 3 phase or 240V single phase, but I happen to know it will run just fine on 240V 3 phase by setting the tap on the power supply for 240V.

My local power company only supplies 120/240V single phase, 120/208V 3 phase, or 277/480V 3 phase. They do not supply 240V 3 phase. If 240V 3 phase is required, then the customer has to supply the proper transformers. I don't know if all power companies are doing this now.

A question, what do you mean by a machine that doesn't use the neutral? Is that to say that the machine doesn't receive the neutral in any way or that the machine doesn't use the neutral to ground out for it's operation (or something similar)?

It is not common for an industrial machine to use the neutral to derive the 120V control voltage, thus very few are supplied with the neutral from the wall. But some home built machines do, as do some home appliances. While the neutral and ground ultimately are connected to earth ground they should not be used interchangeably.

[Al_The_Man]

Here is the NFPA79 schematic for the correct way to re establish the neutral when you use an isolation transformer for either 120v or 240v secondary.
See 1T secondary where one side of the secondary is re-referenced to earth ground. This then becomes the neutral and GND.
Al.

[Parkgrr]

Thank you gents, I really appreciate it, the specific info has given me a lot more confidence that I'm safe to connect to power. I rigged everything up to the 240 delta supply, wired the onboard transformer correctly for the control circuit, hit the cartoonishly oversized power switch and after getting thoroughly freaked out by some super loud (dusty) contactors everything is working great! Appreciate it.

Al, I agree, I've been more than a bit confused why the thing is badged for *only* 208v where the integrated transformer can process about 10 different voltages for the control circuit. I can't tell you how confusing that's been as an industrial power rookie and seeing that my delta supply has ONE 208v and 2 120vs L-N, and then knowing a Wye supplies 208v L-L, it boggled my mind for a long time trying to figure out what it was asking me to give it haha. Luckily y'all and others on this forum (thanks MCPservice) have helped me get out of the woods. Thanks for the schematic.

Good to know about how single phase will supply such a beefy spindle. I just chatted with Yaskawa who told me that this VFD can be supplied with single phase 240v but as a rule it cuts performance by 50%. Not planning to ever use single phase, but nice to know it could be done if needed. Also nice to know that I could run a 7.5hp spindle somewhat happily if I had to (not about to toss a $15k spindle anytime soon though).

So, you bring up one more question:

It is not common for an industrial machine to use the neutral to derive the 120V control voltage, thus very few are supplied with the neutral from the wall. But some home built machines do, as do some home appliances. While the neutral and ground ultimately are connected to earth ground they should not be used interchangeably.

My cabinet takes a neutral with the other 3 conductors. As far as I can tell it does not use the neutral to derive the 120v control voltage so that checks out. However my question lies in that last bit; the machine is wired straight out of the breaker panel for my building so the neutral line going to the cabinet is bridged to ground at the panel, meaning neutral and ground are the same. Is this the situation you've described/is that an issue? I don't think it is but I'm recognizing I have a bit of a blind spot here.

[mactec54]

Thank you gents, I really appreciate it, the specific info has given me a lot more confidence that I'm safe to connect to power. I rigged everything up to the 240 delta supply, wired the onboard transformer correctly for the control circuit, hit the cartoonishly oversized power switch and after getting thoroughly freaked out by some super loud (dusty) contactors everything is working great! Appreciate it.

Al, I agree, I've been more than a bit confused why the thing is badged for *only* 208v where the integrated transformer can process about 10 different voltages for the control circuit. I can't tell you how confusing that's been as an industrial power rookie and seeing that my delta supply has ONE 208v and 2 120vs L-N, and then knowing a Wye supplies 208v L-L, it boggled my mind for a long time trying to figure out what it was asking me to give it haha. Luckily y'all and others on this forum (thanks MCPservice) have helped me get out of the woods. Thanks for the schematic.

Good to know about how single phase will supply such a beefy spindle. I just chatted with Yaskawa who told me that this VFD can be supplied with single phase 240v but as a rule it cuts performance by 50%. Not planning to ever use single phase, but nice to know it could be done if needed. Also nice to know that I could run a 7.5hp spindle somewhat happily if I had to (not about to toss a $15k spindle anytime soon though).

So, you bring up one more question:

My cabinet takes a neutral with the other 3 conductors. As far as I can tell it does not use the neutral to derive the 120v control voltage so that checks out. However my question lies in that last bit; the machine is wired straight out of the breaker panel for my building so the neutral line going to the cabinet is bridged to ground at the panel, meaning neutral and ground are the same. Is this the situation you've described/is that an issue? I don't think it is but I'm recognizing I have a bit of a blind spot here.

Any VFD Drive can run on Single Phase the thing you have to watch out for is the input current rating of the VFD Drive so if you had a 10Hp 240v motor that would be around 50A x 1.73=86.5A so the VFD Drive would have to have an input capacity of greater than 86.5A or it would fail using single phase supply would also have to be able to supply the Amperage to run this motor

Neutral should never be bridged only at the building service any other Neutral connection should be Ground isolated that would not be code if they have it bridged, could be dangerous for your health also

[Al_The_Man]

T
My cabinet takes a neutral with the other 3 conductors. As far as I can tell it does not use the neutral to derive the 120v control voltage so that checks out. However my question lies in that last bit; the machine is wired straight out of the breaker panel for my building so the neutral line going to the cabinet is bridged to ground at the panel, meaning neutral and ground are the same. Is this the situation you've described/is that an issue? I don't think it is but I'm recognizing I have a bit of a blind spot here.

In a normal residential installation, the neutral and earth GND should only come in contact at the panel, if you have any kind of control transformer where the secondary provides isolation, you are allowed to re-reference the service ground to one side of the secondary to (re)-set up a new neutral conductor,
As shown in post #7,
Al.

[Jim Dawson]

My cabinet takes a neutral with the other 3 conductors. As far as I can tell it does not use the neutral to derive the 120v control voltage so that checks out. However my question lies in that last bit; the machine is wired straight out of the breaker panel for my building so the neutral line going to the cabinet is bridged to ground at the panel, meaning neutral and ground are the same. Is this the situation you've described/is that an issue? I don't think it is but I'm recognizing I have a bit of a blind spot here.

A ground is described as a ''grounded non-current carrying conductor'', where a neutral is described as a ''grounded current carrying conductor''. Electrically they are identical. The ground is a safety device, where the neutral is a working conductor.

This is confusing, especially so because codes vary from region to region. With a residential single phase 240V service, in all cases the pole transformer center tap is grounded. But where the neutral is split off of the ground depends on local codes. It could be at the panel, meter base, or even at the pole depending on local codes. In Oregon we have different rules for different installations, mobile homes and marine services for instance require 4 wires from the pole transformer, Hot, Hot, Neutral, and Ground.