Rotary Phase converter (Do your homework!!!!)

So long story short, I Bought a 1997 CNC Lathe Fortune V-turn 26 total power 28Kw @20-30 HP. Place it in my garage. Like most of us did not realize it need 3 phase and I only have single phase service, 200 amp box, with a 25KVA Transformer at utility pole, feeding my house and my neighbors. I started doing my homework after I had spend all this money, machine, rigging etc. That a cnc rotary phase converter will need a bigger KVA transformer at utility pole. That 25KVA is not going to cut it. I guess where the confusion is some people are telling me 20HP RPC is good and should be ok, some are telling a 60 HP RPC and need to upgrade transformer at utility pole which is a lot of money, and running 3 phase is not an option here. So I was wondering if you guys have any Ideas or suggestions, advice? To make this work, I feel I just bought a heavy machine to get rusted in my garage. So if anyone out there has come to this problem, di you get it fix? and if anyone is thinking of doing this similar scenario, do your homework first.

So how much do they want to change the transformer? Changing the motor for a smaller one is an option. Bob

What is the largest motor on the CNC lathe? Your first post says 20-30hp, is it a 2 speed motor?

Really, you bought the machine and got it moved into shop and just now figured out it is 3 phase?

In complete seriousness - if you do not already know that most industrial turning and milling centers are 3 phase, then you have a very long, hard road ahead of you... I mean, how can you possibly think that a 21" turning center is going to be single phase??? How can a 21" anything be expected to be single phase????

With that said, you need to actually do your homework, first. The motor is plainly listed as a 20 horse motor, just about anywhere you look. If you do your homework, you will find that it is a common sales tactic to try and convince people that are ignorant or otherwise too lazy to find out for themselves that they need a much larger converter than they actually do, by adding up every motor in a machine and over-sizing from there.

HOWEVER...

Being as you are obviously either in a residential garage or otherwise not truly industrial location, I seriously doubt that you are going to be running that thing hard enough to engage every single motor at the same exact time, and at maximum capability. So adjust accordingly. ( pondering that for a moment more, given that you've gone this far, maybe you will... )

You are not the first person to do what you want to do, no matter what it is. ( this or anything else in life ) Do some research and learn from the mistakes and experiences of others.

There are ( and have been ) large numbers of people running 20HP turning centers on 20HP RPC's. Turn your rapids down, for starters.

Good luck.

EDIT - I stand corrected ( slightly ) - they did offer a 30HP optional motor. The key here for you is to figure out which you have and then realize that this is STILL not a deal killer.

The safe answer is the idler motor on your phase converter should be 50% larger than the largest motor on the lathe. This will assure that you will be able to start the largest motor from your RPC. If the largest motor is started first it will contribute to generating the third phase leg of power and the remaining motors should start easily. You might find that you will need to start the largest motor first.

What is the largest rated hp motor on the lathe?

3 phase motors started with 3ph from the pole or a RPC will suck down a very high starting current. VFD's ramp the motor speed up greatly reducing the starting current.

IF you are able to start the lathe on a RPC with your 25KVA transformer I would expect your lights and your neighbors lights to do some twinkeling.

P.S. Yeah you probably should have given some thought to powering the lathe before purchasing it... but we all have to learn some time, we aren't born with this knowledge.

Sorry guys been buzy all day.
Bob , so electric company tell me @ 7k to upgrade transformer to a 50kva, then I got to buy the RPC. So Im looking @10k.
Changing the Motor could be an option, got to talk to Fanuc or the manufacturer.

I guess motor has 2 gears but max kw it will use is 18. Then 2kw for x motor and 2 for z motor, 2kw for hydralic pump. And some other stuff I guess.

I specs I seen on the internet for example phoenix converter, or american RC. Say minimun 25kva tranformer for a 20HP RPC. I might have to give that a try. If it dont work I just wasted $2k.

It's worth remembering that the current ratings of the motors are usually full load - so on a CNC machine, the full load current is really only seen when you've stalled every axis while asking full spindle HP and with the lube and coolant pumps, and conveyor motor, all stalled.. so basically never.

I currently run a 15 HP CNC lathe on a 10 or 15 HP phase converter (don't remember). I can't go faster than 2k rpm, I had to turn the accel and decel down a bit, it trips out on full rapids sometimes, and the lights flicker like a nightclub, but it makes parts. It's not ideal but it works, so keep that in mind.

I'm all for doing things right but in this case it's not going to add up. I am running a Mazak QT15 which I believe is 20hp and other smaller machines on an american rotary 30hp. My pole transformer is either 20 or 25kva not 50. 200a svc on the shop and 200a svs on the house. Lights don't flicker. I don't think you will get this to add up just right you are just going to have to jump in and try it. If it all goes sour well, education is never free! I think you can make it work though.

Keep in mind RPC companies rate the units differently. A Kay or Arco rate theirs by the largest hard starting motor it will start. Other like AM and Phoenix rate theirs either by total load or by easy start so a 20 hp AM is equal to a 10 hp Kay. I may have my comparables off a little but you must talk to each manufacturer with your needs to get the right unit. Dave

There is a slight change that you could run it mostly from single phase. Spindle VFD might work ok with only single phase input with maybe up to 30-50% of rated hp, same with servo drivers. Some motors like coolant pump may still need the 3-phase.
Downside is that you are running everything in reduced power and you need to do A LOT more homework to even see if it is possible.

I run a similarly sized turning center AND vmc with a phase perfect 380, 150 amp input single phase at 240 volts . . . no problems what so ever.

I looked at less expensive rotary converters, but their price was a bit more expensive than I was willing to gamble with, so went for the 'sure thing'. For several reasons (noise, power consumption, convenience etc I am delighted with my choice.

My 15 HP axelson data plate says it's 39.5 amps,are u sure it's 20 hp?
The 36" DoAll saw is 15 HP and 50 amp.


Sounds more along the lines of 10-12 actual HP at max amps