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Phase converter for a k&t 315 ch - maybe?, to good to be true

Jemert

Plastic
Joined
May 6, 2018
I am looking to power up my mill but discovered it has a bigger motor in it than it is supposed to have. The mill is supposed to have a 15 hp motor but instead has a 20 hp. My dilema is that there is a 30 horse phase converter for sale that is a third of the new listed price. I have been told that the phase converter needs to be twice the size of the main motor on the mill, so it would have to be 40 hp phase to start the oversized 20 hp on the mill. Is that accurate advice or do you think i could get by with the 30 hp phase converter?
 
You will be fine with the 30HP converter. 2X on size is not a fixed or even calculated value. You will never start under a hard load and you can dictate how much actual load (HP) your throw at the the spindle. Just monitor the 3 phase voltage balance while loaded hard to ensure all is good.

I have not found a rotary RPC manufacturer yet that really understands machine tools or CNC equipment, but they are happy to recommend a BIG one.....
 
The 315 is a big mill (though I had bigger)so I'm wondering what else you have in the shop and how it's getting powered? You don't have to worry, I doubt you will be using max HP on the mill anyway. I had a 4K size K&T with a 50HP motor, it had Wye start and Delta run. I ran it on Wye all the time and never stalled it even with heavy cuts. What is the RPM of the motor? Also the 315 has a motor that runs the feeds so that will add to the load but shouldn't be a problem either.
 
Thank you guys so much for the helpfull information on the converter sizing. I missed out on the deal with this particular phase converter but i will use your helpfull advice with purchase of one when the time is right. I guess i need to do alittle more homework on this subject.
Thanks again!
 








 
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