View Full Version : 208 - 460 volt conversion (Bought another machine)

09-12-2010, 02:09 AM
I've been sitting on this for awhile but I guess it's time I let the cat out of the bag.

I liked my first K&T 2D so well, I decided I wanted another one. This one is the same as my first one, only it's about 10-15 years newer, a three axis DRO, and a PTO rotary table!!

But the tag on the electrical control box says that it is setup for 460 volts. My shop has 208 volts. What should I do?





Bruce Griffing
09-12-2010, 09:19 AM
I would start by finding the dataplates on any/all motors in the machine. My guess is that the DRO is already set up for a lower voltage - but maybe not. The motors could go either way. If the motors are single voltage, call American Rotary about a transformer. They have very good prices.

09-12-2010, 12:27 PM

That machine looks familiar. Was it for sale on PM recently?

I'm afraid you've gotten hopelessly addicted to old iron and, as your friends, we need to stage an intervention. We need you to sit down, be calm, and contemplate your problem. Acceptance is the first step. In the meantime, we need to remove the addiction from your sight. I've got room for one of the K&T's and a Pacemaker, so I'll take those. I'm sure some of the other guys will step up and help out too :D

09-12-2010, 12:39 PM
First check the data plate on the spindle motors. Many times they are multi-voltage even thou the machines data plate says 460v. (as was the case with my Cincinnati T&C)

09-12-2010, 02:15 PM
Geez Tom,you're gonna end up with a machine shop yet.

How about a nice boring mill? Bullard VTL maybe just to breakup the monotony:)

doctor demo
09-12-2010, 03:11 PM
Hey Tom, here's a (nice) K&T You could probably pick up for spare parts.


09-12-2010, 05:43 PM

As mentioned above, first thing to do is check the nameplates on all of the motors to see if they are dual voltage. One thing to remember is a motor may be listed as 240/480 but it will work quite well on 208 with just a little loss of horsepower. The nameplate states that the control circuit is 115 volt so that is no problem. Worst case you will need to change out the control transformer. Now for the bigger issues... If the motors are rated for 240 volt you will need to check the motor fuses, contactors and overloads. On 240 the motors will draw twice the current so fuses and overloads will need to be up-sized appropriately and the contactors may need to be up-sized also. Also, the wire feeding the motors may need to be up-sized. After checking all of the above it might be more practical to just buy and install a 208 X 480 3 phase transformer and leave the machine alone, cost would be the determining factor. The nameplate says 460 at 30 amp (24 KVA approx). Figuring inrush currents I would look for a 50KVA transformer and that will give you a little more 480 3 PH for other things. If you find a larger used transformer all the better. Now just so I don't get flamed :D , also check how much service power you have at 208 and remember even with a transformer the 208 side will be a little more than twice the 460 side current and therefore power (KVA).


09-12-2010, 09:25 PM
Nice try, Stuart :D You're right, this was the one on PM. I haven't been over there in a long time but I got an email from the seller. They were moving and pretty anxious to get rid of it. He told me to make an offer, so I did and he accepted!

Now you two trouble makers better quit it or I'm going to end up broke before I'm 30. I did look, pretty seriously, at a boring mill at one point... I think this will be my last big machine for a couple of years, though. Maybe just one more lathe ... a long one this time. :o :)

Thanks Bruce, Joe and Robin. I'll check it out. At least one of the motors on the machine was rated for 220/460 so I think they all may be. I didn't know what else I would have to change. I had it in my mind that there would be a bunch of relays or contactors that would have to be changed.

I wouldn't mind having a big transformer, though. I've got another mill (Milwaukee #2 vertical) and it's setup for 460, too. It needs a lot of work before it ever runs, though. In fact, I may just part it out.

So ... where should I go to shop around for a transformer? I need to check out American Rotary, apparently. Anyone else?

Thanks a bunch, guys!

J Tiers
09-12-2010, 11:13 PM

There are usually heavy electrical surplus places (basically junk dealers) in any bigger city. We have one, Chicago will have a couple or more.

NEW transformers are expensive. Used, much cheaper. The only problem is finding smaller ones..... usually 45 kVA is a small one for 3 phase, then you start to find the single phase "4-way" units at a few kVA.

09-13-2010, 03:07 AM

Check this one, it might be close enough to go pick up.


This one is farther away but it is a great price and it is 112.5 KVA:


09-13-2010, 10:57 AM
Thanks guys! I'll have to do some checking around. Getting a used one looks like a pretty good solution.

I have another question about this three phase power buisness... on those ebay transformers, the high side is marked as being a delta configuration while the low side is marked as a wye configuration.

The three phase power in the shop comes in as delta. Can I still use these transformers?

09-14-2010, 03:51 AM

For simple 3 phase to 3 phase transformation (OK, I got to use a big word ;) ), Y or delta makes no difference, all will work equally well.