[fcdc]

I bought a Chinese CNC machine which requires 3 phase 380v electricity, but the 3 phase transformer only has 360v ( actual reading is around 370v) which is fine as I was told the manufacturer.
The problem is that the machine needs four wires( three live wire and one neutral/null wire), the transformer only has 3 live wire connection, so we run a neutral/null wire directly form the electric/circuit box.
But the manufacturer told me that is not the right way to do it. However, there is no way I can connect the neutral/null wire to the transformer since there is no slot for it to connect.

PLEASE PLEASE anyone who has bought a 3 phase chinese machine or anyone who knows how to solve this problem help me!!!!!!!
Any suggestion/helps are greatly appreciated!!!

[Eldon_Joh]

they are probably concerned you have a delta connected transformer or the output of your transformer doesn't have the wye point grounded.

if that green wire is ground, then you don't need a neutral.
Or it means they should have had a 5 wire hook up, 3 phases neutral and ground.

if you assume that green wire is the neutral of 380v wye, you'll have 220 volts between each phase and "neutral" which in this case also happens to be ground

[123CNC]

Agree with Eldon, I can't read Chinese, and if they were following any kind of standard, the fourth and green wire on your hookup terminal would by most standard mean it is a Ground.

Personally, I would trace the green wire as far and as many places in the cabinet as I could to verify this. As there is only one wire at your -terminal in the photo, this not the 'one and only one' central ground point. I would trace this to that central ground if it exists. If not, if everything clearly (lableled) traces to neutral connections, I would be a little more concerned that is likely a neutral only and no grounds.It sounds as though you had or acquired a transfomer to step up/down your 3 phase for this machine? Judging by the wire gauge and the toroid transformer to the left in your photo I would guess a very light load for your machine. I would look to see where 3 phase is absolutely required and if those motors or components could be reconfigured for lower/higher voltage. Example, if only a spindle motor requires 3 phase, determine delta or wye, and the possibilty of using VFD to address single to 3 phase power needs.It would then be a matter of figuring out what the easiest, cheapest, quickest, way to address the machine side or electrical supply side to get her going.

Did they provide a full electrical schematic of your machine. That would help others to help you. If you could also provide a little more info on the electrical service you have available to you, such as geographical location (country), single or three phase main, and then any transformer or conditioning you have or are attempting to use to meet the equipment demand.

I'm more familiar with US standards and more of a layman's perspective. But plenty of good people here to help. Good Luck.

[fcdc]

First, thanks for reply. The blue arrow means neutral wire, and first three wires are live wires.
I am in New York City. The electricity input is 1 phase 110v before the 3 phase transformer .
As you can see from the photo =, there are 4 wires on the bottom connection. the White color wire is supposed to be neutral ( but there are no neutral connection in the transformer so we run the neutral line directly from the electric box which is not 3 phase.
The reading between white wire and black is about 60V, between white and blue is about 300v, and whtie and red is about 340v (the reading should also be 220v according to the manufacturer).
Unfortunately, I dont have the electrical schematic( asking the manufacturer for one, but it is doubtful).

I also try to use ground wire(green color) instead of neutral wire, but nothing works.

However, for the dust collector (also 3 phase) it works fine, but the dust collector only has three live connections, no neutral wire.

So I am kinda lost now. I also have hired electrician but they dont really know what to do. But buying a new transformer with 4 wire connection( three live and one neutral) was suggested.

Thanks a million guy for the help!!!!!
Great Appreciated!!!


Attachment 285262

[fcdc]

also, the cabinet is does not have ground wire, only live and neutral wires.
I was told that the machine should be grounded by connect a ground wire to the machine body and the other end to the copper rod in the ground.

[123CNC]

OK, there is no way you will able to use a transformer alone to get from single phase to three phase. Your output reading demonstrate this, two high potentials 300 and 340, and a near neutral 60 V.

Good news is that it sounds like your dust collector is indeed single phase and runs off the first two circuits (red wires). Typical practice for acceptable voltage to inductive loads like motor is+10 %, in your case +38 V, or 342 to 418.

Although it is common in the CNC world, at least with big brand controllers, +3% leg to leg is specified.

If the manufacturer has the component's on the equipment properly grounded to your control panel then yes, you could run a single ground to a separate or local copper ground stake. It is more common that the ground is run from your main breaker panel to the equipment, as your main should already have a connection to ground per national and local code.

Their 'just connect to the machine body' to ground and only having a neutral connection in the cabinet would concern me about their implied grounding practices. You may end up with spurious electrical noise' issues, lost or extra steps, speed control issues, limit and homing issues.

Without an electrical schematic, you can either take it on faith that the manufacturer's wiring is fine and just resolve your supply issue. Or, you will need to come up with your own schematic or understanding of where 3 phase is needed, delta or wye, and voltage(s).

If taking the faith route, you need to address the 3 phase requirement from a single phase 120/240 V utility supply. Common methods to address, rotary phase converter, static phase converter, or Phase Perfect ($$$ trade name microelectronics controlled converter). It is possible the Chinese wired it for a more common to parts of Europe of 380 V Delta, suggested by their instructions 3 out of phase hots and one neutral. See if they can tell you if any of the motors are wound for delta service, or you will need to find the motors yourself and hope it is clear on their data/name plates. Finally, you'll need a step up transformer for either the supply or output of your single to three phase converter. Although it is probably more common to deal with the 3 phase output to step it up to from 240 V to 380 V. You'll need to decide which route first before deciding on converter to match voltage. You will also have to properly size everything.

I would strongly recommend getting more information on what the machine needs as configured, current components and wiring. Assess if motors have any configurable features, dual voltage or delt/wye windings. Then decide on your path forward.

On a whole, my opinion is Chinese machines are getting much better and continue to improve. However their is still a wide range of quality, poor or nodocumentation and language barriers, and unfamiliarity with other standards.

Good luck.

[Al_The_Man]

It looks to me as though the machine has 3 phase terminal strip and the white is actually intended as ground, especially if the green wire on the block goes to enclosure chassis.
IF the machine IS wired for 3 ph and GND then there most likely is a 1phase transformer inside taken off of two phases(1ph) for the computer and control.
With H.V. 3ph and GND a neutral is seldom supplied or needed.
It would be ideal to see a schematic, they should have provided one?
Al.

[fcdc]

First and foremost, thanks you guys for taking time to answer questions and help me solve the problem. Unfortunately, there is no schematic ( still waiting for them to reply).
I will ask the electrician and manufacturer again. The live wires readings are all around 370v to be exact. The problems lies in the fourth one (white color----ground or neutral line).
I will post more comments as I get more information.
Also, Happy Fourth of July, enjoy the lone weekend ( If I dont log in this weekend).

[123CNC]

[QUOTE=fcdc;1725664]
The live wires readings are all around 370v to be exact. The problems lies in the fourth one (white color----ground or neutral line).

This is where you lose me. I understood or misunderstood that you measured the electrical potential, or difference, between each red wire and the green wire (machine sde). In other words, machine red #1 and green = 300 Vac, red#2 and green = 340 Vac, and red #3 and green = 60 Vac. From the output of the transformer you supplied, you had wrote "The reading between white wire and black is about 60V (red#3 & green), between white and blue is about 300v (red #2 & green)), and whtie and red is about 340v (red#1 & green.' Italicized added to corresponding transformer to machine connection.

The live wires or hot are ALL, 2 or 3 live/hot, 370 V when measured relative too what?

A first indicator if you do have 3 phase supply, is you should have near the same voltage when measure line to line. You will also have near the same line to neutral or line to ground for each line. Machine Red 1/ Transformer Out Red/ Line 1/ Phase A relative to Machine Red 2/ Transformer Out Blue/ Line 2/ Phase B = V1
abbreviated, MR1/ TOR/ L1/ PA to MR2/ TOBu/ L2/ PB = V1
continued, MR2/ TOBu/ L2/ PB to MR3/ TOBk/ L3/ PC = V2
continued, MR1/ TOR/ L1/ PA to MR3/ TOBk/ L3/ PC = V3
where V1 = V2 = V3 within 3 - 10%
.
Also L1 to neutral or ground = V4, L2 to N/G = V5, L3 to N/G = V6, where V4 = V5 = V6 within 3 - 10%,
and if neutral and ground available, N to G should be close to zero, in other words relatively low if any.

Of course a voltmeter will only tell you that the three lines all have a potential difference, but not the phase angle. Which in many cases, such as yours will not matter much.

That is why this sentence "The problems lies in the fourth one (white color----ground or neutral line)" is a little difficult to understand what you mean. It's voltage potential relative to what? Per manufacturer, your white line relative to transformer outputs red, blue, or black should approximate 380 V. If your White supply, also their machine Green, is a neutral, it should be near 0 relative to the machine frame and to ground.

Enjoy your long weekend as well, and God Bless America, home of the free, land of the brave.

[Al_The_Man]

Unless I missed it it has not been shown where the white/green wire goes to in the machine enclosure, this is the most important detail.
If going to a ground stud, a neutral should Not be connected to it!.
Happy Canada Day!
Al.

[fcdc]

Hope these two pictures would help a little. Sorry for any confusions. I have operated the CNC machines and laser cutter, but I have never dealt with the electric components. This is way over my head. (Laser cutter is another issue I am dealing with right now, but should be easier to solve).
Once again, thank you for your time and help!
Attachment 285340Attachment 285342

[Al_The_Man]

Where did you get the info from that this was neutral.
There is a white coming in (Neutral??) where is the green (Earth GND?) conductor going to or terminated?
Maybe one of the translate pages may show.
BTW in China Green is the B phase of 3ph supply!!!
Al.

[fcdc]

I am told by the manufacturer that the white one is neutral line. That is all I have at the moment. I will ask them more....

[Al_The_Man]

By now I should not be surprised with Chinese manuf. documentation and support, from some of the examples I have seen.
It is too bad, because if potential buyer would ask the right questions and demand documentation, they would have to smarten up.
It is an old story, It may be cheap, but you get what you pay for.
Al.

[fcdc]

Yes, Al, that is right. Even the laser cutter has manual/document, but it is very general (for example, connect x to y, but where are x and y in the machine???)
It is part of the cost you pay for buying chinese machine. I have anticipated the potential problems, but it is a few too many tbh.
I got the laser cutter to work today, hopefully at the end, I should have the cnc working soon.
Best,
Happy Independence Day.

[123CNC]

Al and all our neighbors to the North, Happy Canada DAY!

FCDC,

In your last photo with your measurement notes, the wires are more clear to me, and seems like everyone but China is on the same page. If it was built to US code, and the manufacturer has said these four terminals are for service connection, then I see a second green/yellow wire on the machine side of the fourth terminal (left to right). Per US code, and most other countries, including the People's Republic of China, green/yellow designates a Ground connection. As I had previously mentioned, seeing multiple wires on this one terminal, green/yellow and green, then good wiring practice would be that this is the ground star point, or the 'one and only' common point for component grounds. As good practice and widely followed, the green/yellow strip is strictly reserved for grounding. Where as solid green, it depends when it was built and who you ask.

Also thanks AL for that new tidbit of green as a common 'Phase B' in 3 phase power in Chinese equipment. Did not know that. Makes FCDC's puzzle even more interesting, especially since they seem to keep telling him it is a neutral. Something definitely lost in translation.

FCDC, what happens when you remove the white altogether, does the machine fully or partially power up?

With the white removed what are your voltage readings from red/blue/black to the open green terminal?

It sounds like you are not too comfortable tracing out wires, but instead you could look for a power supply or the toroid wiring, or any component to see if any green or green/yellow stripe wires are connected to a terminal labelled "G" or the segmented line ground arrow symbol, something like this Attachment 285360 . Without tracing, not a smoking gun, but higher probability your on the right track.

Happy Canada Day and Happy Independence Day! Peace to all!

[fcdc]

Thanks, 123CNC, dont know how to thank you for your help.
I speak chinese, so they definitely told me white wire is for neutral/null line (not ground line).
with the white wire or wthout, the live wire reading are the same 360v between any black/blue/red wires. Also the start button on the cabinet would turn on (with our without the white wire), but that is the only thing would turn on, not even the small fan on the side of the cabinet would turn on.
Happy Canada Day, have a cup a tim horton( i miss tim horton, i went to school in buffalo).
Once again, Thanks mate.

[dmannock]

I posted the international colour codes in the Chinese machines forum. What they do is use whatever wire is used for the domestic market and leave you to replace it. That attitude must change.