Buck Transformers 3

[banshee1]

One of our CNC machines required 220v (+/-10% according to manu.), but the 208v panel was at it's max. load so the electrician wired the machine to the 240v panel and put two buck transformers inline to drop the voltage. His reasoning was the 240v panel was a little over and the manu. was very adamant about the +/-10%.

My problem now is I have a burned out motor and when I checked the voltage of each leg to ground 2 legs show 235/240v and the 3rd leg shows 40/50v. When I check any 2 legs to each other I see 214v on the meter. This doesn't make sense to me from what I understand about electricity. Each leg should be 110v approx. when checked to ground and 220v when check to each other correct? I even see the same readings when I checked the output side of the machines main power switch.

Can anybody explain this? I don't understand/know why 2 legs show 230/240v while the 3rd is so low or how everything works powered like this. I know/understand very little about AC, DC I understand.

We've had the machine for 2 years now and everything works, and from what I can tell all of the secondary motors (coolant pumps, chip conveyors and such) are wired for 220v. The work lights could be wired for 110v, but it's not easy gaining access to them so I haven't verified but the are working just fine.

Thanks.

 

[waross]

Your post raises some interesting questions.
First question: The origin of the motor? 220 Volts suggests either European or Oriental.
Oriental: Many 220 Volt rated Oriental motors are second rate copies made by people who don't understand that 110 Volts has not been a standard voltage in North America for about 60 years.
Quality may be suspect.
European: 220 Volts is a European standard voltage, but at 50 Hz.
One of the important induction motor parameters is the Volts per Hertz ratio. When a motor's supply frequency is changed, the rated voltage must be changed so that the Volts per Hertz ratio stays the same.
When the frequency is changed, the Volts per Hertz Ratio is much more important than the rated voltage.
A 220 Volt, 50 Hz motor has a V/Hz of 4.4
At 60 Hz and a V/Hz ratio of 4.4 the required voltage is 264 Volts.
Your voltages are interesting but possibly explainable.
You may have meter errors if you are using an old analogue Multi-Meter.
Your 240 Volts may be a corner grounded delta system.
Your 240 Volts may be an ungrounded system.
Your electrician may have used a non-standard voltage buck connection.

Each leg should be 110v approx. when checked to ground and 220v when check to each other correct?

Incorrect. For three phase divide by root 3 (1.73), not by 2.

When I check any 2 legs to each other I see 214v on the meter.

This is the voltage that the motor sees. This is less than 3% below 220 Volts and is a good voltage for a 220 Volt rated motor,
IF
The voltage holds up under load,
and
The frequency is correct.
Running a 220 Volt 50 Hz motor at 214 Volts 60 Hz is actually about 19% under voltage.
Expect all the motors to be running hot.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[ScottyUK]

220V hasn't been a officially-recognised standard European voltage for quite a few years, and neither has 240V. The harmonised voltage across the whole EU is now 230V, although 230V isn't always the voltage present at the wall outlet. ;-)

A word of caution on 'Oriental motors': Oriental Motor - as distinct to motors originating in oriental nations - are actually a pretty decent brand.

 

[waross]

Thanks for the heads up on "Oriental Motors" Scotty. They seem to be well aware of international standards.
Your comments on 220 Volts no longer a standard supports my suggestion of suspect quality despite my ignorance of current standards.
You can guess how long ago it was when I spent a lot of time going through catalogues that listed both 50 Hz and 60 Hz voltages. grin.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[banshee1]

Waross, I don't know what the motor itself is rated at yet (haven't had a chance to actually tear it out of machine yet), but the machine itself is rated at 220v 50/60Hz which as you guessed came from Taiwan. I assume the motor itself is from the same country.

No problems with voltage drop under load. At least not enough to trigger any alarms on the machine.

Spoke to the reseller/installer of this machines and he called it a lazy leg and that he's seen it before and shouldn't cause any problems since the machine and any motor should see the correct 214v across any 2 legs. We bought the machine new 2yrs ago with no issues so I'm gonna trust him.

Meter is a digital Extech that has served me well for a lot of years.

Thanks for the education, I was probably confusing it with household 240v.

 

[itsmoked]

Scotty and Bill; 220 60Hz is an extremely common CNC voltage for older CNC machines. Probably 2 out of 3 elderly CNC machines I service are 220V 60Hz. A great many CNC machining centers at 'normal' machine shops are more than 10 years old, 20 years old is common. These machines all come out of Taiwan and South Korea both 220/60Hz places and some out of Japan 220/60Hz back in the day.

Oddly, most have tap settings for the giant control transformer powering everything BUT the motors.


banshee1; The three voltages between each other is the important one. Don't worry about the voltages to ground. With the spindle running that's the real voltage when measuring between all the phases - under load. Your 214V could be dropping some under load and 214 to the system is just fine.

With two transformers, the most common method, the voltages to ground or neutral are reasonable, odd, and reasonable, just what you're seeing.

BTW the spindle is driven via a VFD so it never actually sees the line supply but a rectified to DC then synthesized AC to the spindle.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[waross]

banshee1;
Your voltages look OK.
Sometimes motors just burn out.
Check to see that the motor was not inadvertently overloaded.
Thanks for the info Keith.
I don't see CNC machines.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[MatthewDB]

Your description of voltages to ground sound like your 240V panel is delta with a corner ground. Just by luck one of the phases that is being bucked towards the other phase happens to be the grounded phase, hence the 40ish volts to ground.

As long as the machine is 3 wire you're OK. If there are any line to neutral loads this will be a problem.

 

[banshee1]

Looks like the motor itself is burned out. It's VGS/Shin BAE induction motor. Anybody now of a good place to get an induction motor? Doesn't seem to be real prevalent on the web. I can get one from manufacturer, but I'd like to find a cheaper source.

Thanks.

 

[waross]

How about some pictures? Please include a good shot of the nameplate.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[banshee1]

I'll try to throw up some pics shortly, but here are the specs off the nameplate.
4IK25GN-S5T6
3phase, 4P, 220v, .26A, 1600rpm, 25W.

The only thing really throwing me off is the last 4 values. They don't seem to follow the standard. The closest I can find is a 4IK25GN-SW2T. The S5T6 is probably a tweak the machine manufacturer made to a stock item and the motor manu. made a custom p/n.

Thanks for the help waross.

 

[HCBFlash]

Well Banshee1, you describe an unfortunately common situation: buy a piece of Taiwan junk, and rely on it do make somebody's living here in the USA. Be sure to get your "electrical guy" to rig it up on the cheap. (Well hey, they don't just give them electric boxes away!) Something goes wrong, just Google it. Now you're an expert at this too.

Stay away from me. I don't want the firefighters where I live to be exposed to this. You may not like this, but you need to hear it, loud and clear.

.


Me wrong? I'm just fine-tuning my sarcasm!

 

[banshee1]

HCB, unfortunately there aren't a lot of CNC Machine Tool builders in the US. Mazak being the biggest, unfortunately our budget cannot afford that high of a cost (plus we cannot charge enough per hour to pay for it because our U.S. customers (which is 100% of our customers) wont pay that much. So you think we should have brought another 208v service into the building at a cost of how much $? Again we'd have to charge our customers more (our bills go up, part price goes up) so it's a catch22.

The electrician did everything to code, so explain why there is such a fire hazard? I think you have blinders on, because I bet there are machine shops (or any business that uses machinery) in your area that do/did the same thing and purchase their machines overseas as well.

Even US manufacturers use overseas parts to build their machines (like small motors, controllers) for the same reason. Just a fact.

We're talking about a simple electric motor, so no need to get panties in a bunch. And before you say it I voted Trump.

 

[waross]

Be sure to get your "electrical guy" to rig it up on the cheap.

I have been using Buck and boost transformers to adjust voltages for over 40 years.
There is nothing wrong, unsafe or contrary to code with a properly installed buck or boost installation.
The standard supply voltage in Western Canada is 347/600 volts. There are a lot of legacy 480 Volt installations.
I have seen buck transformers installed to convert incoming 600 Volts to 480 Volts for a power distribution center feeding half of a plant to accommodate legacy 480 Volt machinery.
When the largest oil company in Canada does a shutdown at their major upgrader, they rent 480 Volt generators for temporary power. (Yes there are 600 Volt rental generators available but they are rare. The major rental firms will also rent out a packaged boost transformer package when 600 Volts is needed.)
Then with a temporary distribution system at 600 Volts supplied by boost transformers, they use more buck transformers to drop the voltage back down to 480 volts for rental welding machines and ventilation fans.
There is nothing unsafe, wrong or contrary to code with a properly installed buck or boost transformer bank.
On the cheap? That's a win win situation. An autotransformer installation is much smaller and so much cheaper than a full transformer.
After installation, the operating losses are often much less also.
What's wrong with that.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[HCBFlash]

I know all that.

You'll figure it out.

My post got "softened", but I'll again attempt to point out that this is life at the bottom. When your market won't even support moderate to slightly higher than average quality production equipment to manufacture goods, the customers are not desirable and other markets should be pursued. It wouldn't support well paid skilled machinists using older machines and methods, then poorly paid ones using those methods, and now not high quality automation with high cost labor (any US labor is high cost, relatively, on the global market)

Still, you don't need a Mazak to avoid problems with your production equipment. Just buy equipment made for 230/460 60Hz. But that would only work if the market would support competent machinists and engineers to direct purchasing.

.


Me wrong? I'm just fine-tuning my sarcasm!

 

[HCBFlash]

Waross/Bill, I won't dispute your remarks, or doubt that those installations and temporaries are done safely, sized properly, and correct conductors and OCDs are typically used. You are describing "legacy systems", which are typically being phased out and changed over in an orderly fashion. These are situations that also provide experience for engineers and tradesmen in really getting an understanding of how these atypical situations can be dealt with successfully.

Yet you and I, and many others realize the troubles that accompany these situations, and more importantly the failure modes presented by poor or damaged connections, faulty components, grounding issues, and voltage and current imbalances. Using bucks in an open delta to feed a single machine with motors that small? Not my call.

Of course it's possible. Is it advisable?

Here in this forum, and some others, it's fun to contemplate possibilities and work-arounds for strange systems and situations. If you're an experienced engineer for construction projects and custom machinery you know that simpler is better. Given the choice between typical and unusual, your project timeline, construction costs, maintenance costs, and liabilities all favor the typical. Additionally, the small facility typically has widely variable resources for availability and quality of engineering and skilled technical help to service situations like this, and people like this OP get drawn in, because, "it's really no big deal, just make it work, go on the internet and see what you can find..." etc.

Cutting corners always involves safety, quality, workmanship, and people including bystanders. It's hard not to press (and err) toward "protectionism, nationalism", etc. when imported items of recognized inferiority are so typically involved. Where I and the OP live and raise our kids, higher quality and operating standards existed for the generation prior to ours, and were sacrificed to "the global economy".

I had an admin soften and edit my 1st reply on this thread, It was harsher and mentioned some fringe and cash market players by name, because I know about this stuff. I don't think anyone wants this site to become an industrial DIY, fix it yourself site. That's sure not what it used to be.

.


Me wrong? I'm just fine-tuning my sarcasm!

 

[waross]

Some people learn new things on Eng-Tips, some don't.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[banshee1]

HCB, what I was trying to get at almost every machine from overseas is wired for 220, so to have a machine wired for 230/240 would most likely require a U.S. built machine (which is why I mentioned Mazak). And U.S. manufacturers of CNC machines capable of doing the work we do is very small. We've been in and out of very different markets (power generation, military/defense, medical, firearms are a few) and they are all the same.

If we had another 208v service we would have used that and not needed any buck transformers.

Granted I know very little about AC, but with the 220v +/-10% requirement of the machine, even with the slightly over 240v we have I doubt it would have been a problem. Large over voltages I know are bad, but I wouldn't think 3-5v would make a difference.

If I'm wrong please let me know. I posted my question to learn, not receive DIY fix it info with the exception of asking if anybody knows where to get induction motors. If you can supply info/stats (hard evidence) stating that supplying small motors with buck transformers is detrimental or unsafe please send them to me. I want to know so I can inform those that make these decisions of issues that could arise. Typically machine tool builders will use smaller 110/115v (single phase) motors for light duties (like the motor I need to replace) so if there's only 220v 3phase coming in how is this done?

I was not involved nor have any say in the powering of our machines, we hire outside people with hopefully the correct knowledge. I wouldn't think they wouldn't do anything unsafe and take a chance on losing their license.

Like you said HCB, standards aren't the same anymore even in my trade. There are machinists and there are operators. You give a machinist a print and some material and he can get it done. An operator (or button pusher as we call them) need to be told everything and cannot solve problems. We have our machinists set up and prove out the operation then we stick an operator on it to finish the order cause all they have to do is push the green button or push the red one if things go bad and they get paid considerably less.

 

[waross]

banshee1; I am not surprised that you are looking for a second source for the motor.
I have seen switch gear priced by the same office as replacement and as new equipment. The price for new equipment was a competitive bid and was 25% of the replacement price.
A second source at a better price is just good business.
Have you looked at this web page?

http://catalog.orientalmotor.com/ke...25GN-S&refer=http://catalog.orientalmotor.com

As for the motor number, 4IK25GN-S5T6, the S5T6 probably indicates a special integrated gear box.
It may also indicate a special shaft and possibly a special flange mount.
There is a very good possibility that you may be able to rob a 4IK25GN-xxx motor for the stator and probably the NDE cover.
As long as the standard voltage in Canada is 600 Volts and the standard voltage of our largest and nearest trading partner is 480 volts we will continue to build the legacy.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[banshee1]

Bill, I did come across that website (actually only website I found that has these induction motors) in my search. Since it's an option to purchase this motor already attached to a gear box, I agree that the S5T6 probably has something to do with that (no p/n on the gearbox on my machine so probably only available as a complete unit from the machine tool builder).

I need to take the motor off and measure the output shaft to make sure it matches the standard 4IK specs. If it does I think I'll pick one up that most resembles mine and hope for the best.

Thanks Bill.