Need Help!- Auto or Isolation transformer for Mori Seiki AL2 fed by rotary?

[pld0vr]

I have a 1990 Mori Seiki AL2 lathe, which I have an american rotary phase converter system to create 3 phase power.

Because the machine expects 600volts, I need to run my 240 3phase created power into a transformer in order to step up the voltage.

The machine has a small internal transformer for the controls to step the voltage back down, and I believe the motors run at the supply voltage, but I'm not entirely sure. There seems to be only one small transformer inside the machine, which appears to be an isolation delta transformer as there are 3 coils there, and not one which would indicate an auto transformer.

So... the main question is do I use an Auto or Isolation 15KVA transformer for the machine. Do I need the "protection" of the auto transformer, or is it not really beneficial since I am running on generated power anyways and the controls already have another transformer internally?

My understanding is that isolation transformers are not quite as efficient as auto transformers, which is of concern to me because I am run at the edge of available amps to run the machine before tripping the breaker.

Auto transformers are 1/3 smaller and more affordable, but isolation transformers protect from voltage spikes, etc.... however since I am on residential power anyways is that even a concern to me?

My thought is that the control is already protected by the internal isolation transformer on the control side, so I should be fine with an auto transformer either way.

Thanks for your help!

[Al_The_Man]

Personally I would look at seeing if you can bypass the whole of the 600?
Why transform up to 600 when in all probability the machine converts it all back down to
240v 3 phase anyway, unless there are 460 only item.
Most drives are at 240v, the exception could be the spindle drive which if DC may have a 460/240v star secondary with the star used as common for the SCR controller.
But it may be worth the check to see what you can actually run on 240.
In some case you may have to confirm fuse and wire rating.
Al.

[mike_Kilroy]

Al has great idea to check out. If you do find you need a transformer, I'd like to comment on some of your perceptions of auto vs iso.....

Originally Posted by pld0vr ......There seems to be only one small transformer inside the machine, which appears to be an isolation delta transformer as there are 3 coils there, and not one which would indicate an auto transformer.

a 3ph auto xfmr will look exactly like a 3ph iso xfmr - still 3 coils they just have one tapped winding per phase instead of 2 separate windings per phase.

Do I need the "protection" of the auto transformer, or is it not really beneficial since I am running on generated power anyways and the controls already have another transformer internally?

Not sure what you mean by 'protection?' that is the one thing a buck-boost or auto xfmr does not give you

My understanding is that isolation transformers are not quite as efficient as auto transformers, which is of concern to me because I am run at the edge of available amps to run the machine before tripping the breaker.

Both auto xfmr and iso xfmr should be around 95% efficient. There should be no difference in efficiency between them.

Auto transformers are 1/3 smaller and more affordable, but isolation transformers protect from voltage spikes, etc.... however since I am on residential power anyways is that even a concern to me?

Yes! the iso xfmr does provide a level of protection against spikes transferred thru the magnetic field between pri and secondary while the autoxfmr.s pri and sec being the same winding let it thru easier. Should you not be concerned cuz u r residential? Not sure this has any bearing on it. The same spikes come down the power lines to my house from close by lightning strikes at go to the machine shop in town. These are 7200v lines out our way in the country and I believe they are often 3ph and they just split them down 1ph to the houses or run all 3 to the businesses needing them.

My thought is that the control is already protected by the internal isolation transformer on the control side, so I should be fine with an auto transformer either way.

Fair enough thought.

[pld0vr]

Okay.. I had another look inside cabinet. The cabinet says "input voltage 550volts 60hz/ 600volts 55hz.

However, on the transformer there are a number of voltage taps. It has suggested connections for input of 220volts to 600volts.

Now, does that mean that I can feed the machine with 220 volts directly? I am going to assume that this is only for the control unit, so would the machine correct load on the spindle and axis motors for a different feed voltage?

[Al_The_Man]

If the taps are on the primary then it would point to being capable of 220v 3 phase input.
Check the cable sizing from disconnect to transformer to ensure the higher current capability.
BTW what controller does it have? Fanuc? if so what model?
The 6 etc expects the correct phase rotation at hook up.
Also if it is a DC spindle, there is most likely a transformer for it with a 3 phase star common for the SCR drive.
This should be checked.
Al.

[pld0vr]

Originally Posted by Al_The_Man If the taps are on the primary then it would point to being capable of 220v 3 phase input. Check the cable sizing from disconnect to transformer to ensure the higher current capability. BTW what controller does it have? Fanuc? if so what model? The 6 etc expects the correct phase rotation at hook up. Also if it is a DC spindle, there is most likely a transformer for it with a 3 phase star common for the SCR drive. This should be checked. Al.

It's a fanuc 10t. There is also a second transformer, but it's quite different looking and has no taps. I'll try and trace the wiring, but with only 3.5kva that can't feed the entire machine. The spindle is 7.5/10 hp.

[mike_Kilroy]

pictures are worth a thousand words? why not post a picture of this transformer?

Why not call Mori S. and ask them if you can simply change the taps on that xfmr and make everything then 220? You might get the answer; worse case they will tell you to go take a hike?

"Small transformer inside" with 3 coils is not a control transformer for nc and stuff; 3 coils tend to be the main input power to a machine so you are likely going to be able to retap that puppy and be good to go - but you should be sure...

[Al_The_Man]

I have all the prints for a Hitachi-Seiki 1985 lathe with a 10T and interestingly they do not show any main power transformers, just 220v into the breaker for everything, including the spindle .
It is almost as if the end user supplies the matching transformer.
Do you have prints for your model?
Also If you do not have all the parameters saved or hard copy including the 9000 option parameters, I suggest you save them ASAP after you get it going.
Al.

[pld0vr]

Originally Posted by mike_Kilroy Not sure what you mean by 'protection?' that is the one thing a buck-boost or auto xfmr does not give you

Sorry, that was a typo. I meant protection of the iso transformer.

[mike_Kilroy]

i sorta figured that the next day

[pld0vr]

Originally Posted by Al_The_Man Do you have prints for your model?

I wish. When I bought it I was told it came with manuals, but it came with nothing. They also lost the coolant tank and wouldn't replace it. If you know where to get one, let me know.

Originally Posted by Al_The_Man Also If you do not have all the parameters saved or hard copy including the 9000 option parameters, I suggest you save them ASAP after you get it going. Al.

I've heard this, and I'll get on it for sure. The main board was replaced in 2003 already.

[pld0vr]

Originally Posted by mike_Kilroy pictures are worth a thousand words? why not post a picture of this transformer?

Good point. Here are the photos... best I could do with my big camera.



On the right it says control 110v



Look at those tiny wires. Are you seriously telling me that runs the machine? I can't see that being possible. Besides only 3.5kva? I was recommended a 15kva transformer to run this thing.



Notice the second bus bar on the rear with what looks like small voltage corrections? Not sure.





That black thing labeled T2 is the second transformer.

Thank you for your help. Appreciate the effort either way.