can I run different volt machines off one xfmr?

I am thinking to the future and was wondering the best way to run machines with different voltages. I have 240v with a RPC for 3 phase (currently 15hp) I also have a 440v drill press and also a line on a 380v machine as well as a 575v machine. My question is can one transformer be used to power all the different voltage machines? I am thinking a larger version of the one in the link. The output could be on some sort of three way switch so only one could be powered at a time. (if that is critical) I am one guy so probably not to worried about running more than one by myself but...

Here is link to one on ebay that is to small but has all the taps:
FLASSHOFF KLOSTERBERG ETKJP, 2,2 KVA, 22-575 VOLTS TRANSFORMER | eBay

Yes, just need a tap switch. Don't try switching under load, though. Things could get interesting if you do.

Why not rewire the machines for a common voltage, sounds like 460/480 would be the pick of the litter. The transformer size should be 15 to 20 Kw.
Tom

edit:- While what I said above is correct, its needs a little clarification. The transformer needs to be on the secondary side of the RPC and needs to be 3 phase.

I took it for granted that you know you can't put the transformer between the power line and the RPC. Further, there is no need to use the transformer on the 230 v machines, these could come directly off the RPC. If the 380 volt machine is 50 hz, then it could be run of 60 Hz as long as the added speed doesn't affect the machine function. So now you only need a 230 volt in, 460 and 575 out, 3 phase transformer.

T;-

It seems common to find 575 input to various lower output voltages, kind of opposite the ones I linked to.
I think the 575 mill has 3 motors, maybe special ones, not positive. Not sure what motor is on the 380 machine. The 480 drill press I own has 2 motors & can be rewired to 240v, which is what I was going to do, but then found the other two...

It is possible to supply different voltages for different machine if you know what you are doing. I have three single phase transformers which simultaneously supply 120, 208, 240, and 480 three phase distributed to different outlets. However, I had to derate the transformers because I used windings that normally paralleled for separate uses. As I said, you need to be used to juggling windings around.

Bill

Another option is have a separate convertor for each voltage. I have 230 and 460 in the shop, two different convertors. For 460 I jack up the input voltage to the RPC to 460 with a single transformer.

Transformers can be run backward. If you find a 230/460-575 with the 575 as the primary, run it with 230 on the 230 taps. Take 575 off now secondary and run the motor.

Tom

edit:- Looking at ebay, I see a number of 480/575 volt to 115 v 3 phase transformers. You can also use the transformer in autotransformer mode, feed 480 in that 575 out, tape off the 115 volt. With this, there is no isolation of the primary to the secondary.

T

TDegenhart said:

I took it for granted that you know you can't put the transformer between the power line and the RPC. Further, there is no need to use the transformer on the 230 v machines, these could come directly off the RPC. If the 380 volt machine is 50 hz, then it could be run of 60 Hz as long as the added speed doesn't affect the machine function. So now you only need a 230 volt in, 460 and 575 out, 3 phase transformer.

T;-

Click to expand...

And where does he get the 380 in your scheme?
If that is a German machine (Deckel perhaps) likely the motor is single voltage and dual speed.....Will run on 60 Hz fine, but will need 380 , a rewind, or a new motor.....
Cheers Ross

AlfaGTA said:

And where does he get the 380 in your scheme?
If that is a German machine (Deckel perhaps) likely the motor is single voltage and dual speed.....Will run on 60 Hz fine, but will need 380 , a rewind, or a new motor.....
Cheers Ross

Click to expand...

Read the reply carefully. As long as the rating is 380/50 then it will perform electrically identically because the volts/Hz is the same. The motor will run 6/5 times faster. This may or may not be a problem.

Tom

There are 3Φ autotransformers available that can do what your asking, but not with a switch as your asking.

The switch part of it means you making different tap connections with a wrench or screwdriver, not the most convenient but doable if you must.

These type units are rare, expensive, and normally built to a OEM specification and part #, and the labels not always crystal clear on what it is.

These units used can be found on CNC machinery built for the world market. Here is a current ad on Ebay for a typical unit. take note it's from a Mazak machine. 23KVA and all of the voltages you would need except for the 600V Canadian one.




And any transformer builder can make what you need, if you got the money. A local builder to me offered some in their old catalog.


But a cheaper and more sensible way, is to standardize to two shop voltages at a maximum, and then convert any machine individually to either one of those voltages. Either by rewiring and modifying controls on each or by putting smaller transformer banks on the machines for the ones that can't be converted.

Have a look at this Catalog for some samples of how different voltages can be obtained when necessary. Pg 30 & 32 in particular, and more general information elsewhere.

380 to 415 50Hz machines can normally be run on 460 60Hz with a 20% speed increase, as others have mentioned. 600V can be obtained from 480V by using two smaller 1Φ 4 winding standard units as shown in the catalog pages above. 200-208V can be bucked down from 240V, or use a isolation transformer if you need a wye output.

SAF Ω

Any kind of custom transformer like that will likely cost you a lot more than you think, especially compared to buying used.

You only need two transformers; one for 240-480V, then a second one to boost the 480 to 600V for that one machine. You do NOT want to transform to 380V because there is a 99% chance that your motor is 380V 50Hz, and you have 60Hz, so that motor will be perfectly fine getting 480V 60Hz (as was explained earlier). If you transform down to 380V, but give it 60Hz, then the motor will only deliver about 63% of it's rated torque and might stall out easily or over heat under load. There is no need to do that.

I do not think you need the switch.

If you find a unit with the taps you need, you can just wire the machines to their voltages. They will do nothing unless turned on.

Even if all were turned on, as long as each tap is not loaded beyond it's current capability, AND the total VA of all loads is below the maximum for the unit, you ought to be good.

Concur on the 380V..... but DO take a look just to make sure some odd thing was not done at some point.