Need help re: transformer and KVA requirement

I am needing some imput regarding a transformer.

Here's my situation. I have a Nardini 1440 that I have been using for a few years with no "real" problems. The motor is a dual hp rated WEG motor 3/6hp. It is a single voltage 440v motor. I have been running this on 220v 3ph power with no issues other than occasionally it won't get up to speed immediately and in that case I flip it off and then on again. When on, it operates smoothly and quietly and no problems bogging down with heavy cuts, etc.

I have recently been told that this is bad for the motor and that I need a transformer to prevent premature motor failure. Sooooo, my question at this point is, what is my MINIMUM KVA requirement for this lathe motor to function properly?

I am currently running my machines off of a 30hp rpc that is fed by 50amp supply. Yes, I said 50amp. It works and that is all I have.

I have been told I need a minimum of 20kva, but someone else has said that according to the calculation, a 15kva will be more than adequate and even a 9kva is theoretically okay.

Anyone here want to chime in??

Thanks in advance!!!!----Grant

Grant,

Here ya go.

I figure you are looking at about 6-8 amps maximum (run) on that Weg at 440v. You can use the calculator below. I got 5.33KvA at 7 amps.

http://www.t-r.com/TransformerCalculator.aspx

I just remembered I have a small, wall mount, box style 480D-240D Cuttler Hammer 9KvA as well. I just have to find it.

What's the motor's frame size? Just curious.


Hope this helps,

Tanner

440 mtr on 240

Check the motor amperage when under load, if it doesn't exceed the service factor amps on 480 you are not hurting it at all. A plus is it starts nice and soft.

Before I would invest in a transformer, make sure that the weg motor is not a 230 volt motor instead. I find it hard to believe that you can run a Nardini 2 speed lathe on half the voltage, as this lower voltage applied would change the horsepower from 6/3hp to 1.5/.75hp.

macplus said:

Before I would invest in a transformer, make sure that the weg motor is not a 230 volt motor instead. I find it hard to believe that you can run a Nardini 2 speed lathe on half the voltage, as this lower voltage applied would change the horsepower from 6/3hp to 1.5/.75hp.

Click to expand...

I know for a FACT it is single voltage 440v ONLY That is what is so perplexing.
It has a ton of power. For instance, I was parting using a large parting blade 1.25" x .25" and it bound up and exploded. Now, to get the blade to shear vertically takes W A Y more than a couple hp. Shot pieces of blade everywhere. The machine gave a little grunt right before it blew apart.

That IS perplexing, a single voltage motor with dual horsepower ratings.

Could it be possible that the motor has been reconnected or rewound for 230vac..is there any overload protection built into the lathe, as you could check the overload ratings...that might give you a idea if anything has been changed.