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Best way to power up my new machine

CPIindustries

Plastic
Joined
Sep 20, 2017
I'm in the process of buying a cnc for my house. I have run into a few problems. I was planning on getting a VFD to run it since it is 3 phase but realized they don't make them big enough for single phase input. The motor is a 10hp but it says 10/15 which I'm guessing means max draw for the 15hp. 230v 3 phase and a full max draw of 65amps but normal use about 36amps. I know I can go massively oversized on a 3 phase input vfd like 30hp to make up for the 50% derate but I would need to shut my house power off whenever I wanted to use it since I would need like a 125 amp breaker for it and I'm sure if you can run a vfd that large single phase. I looked into digital phase converters but that's gonna run me like 3200$ base and also needs about a 125 amp breaker the guy told me. My next idea was what I didn't want to use which is a rotary phase converter but am not sure what size I should get and also I believe will require probably a 100 amp breaker which is what my garage subpanel is. Anyway could definitely use some help on this maybe people who have run into the same problem and what you did or should I just scrap my plan of this machine and look for something with a smaller motor or just look for a minimill and eliminate this headache I'm causing for my self haha.
 
Forget a VFD. A VFD can run a single motor. It cannot run a CNC machine with multiple motors and drives.

I suggest you get the biggest rotary converter you can run with your power. 100 amps should run a 20 horse converter. That should be enough to run your machine in most cases. Most home gamers are not pulling full load amps with their machines.
 
Forget a VFD. A VFD can run a single motor. It cannot run a CNC machine with multiple motors and drives.

I suggest you get the biggest rotary converter you can run with your power. 100 amps should run a 20 horse converter. That should be enough to run your machine in most cases. Most home gamers are not pulling full load amps with their machines.

Well I know for a fact a VFD can run a cnc I know a handful of people that do it flawlessly on 220single phase they just have smaller machines than I have. The problem I have with rpc is the variable speeds you get with a cnc make it hard for it to keep up since it's constantly speeding up or slowing down. I know it won't draw the full 65 amps probably ever but I'd like to be overpowered in case it ever happened.
 
VFD's are not intended for this purpose phase converters are. I have a 30hp american rotary that I run a 20hp mazak lathe and a 10hp Brother tapping center off of (not at the same time). It has a 125a breaker out of the panel. I consider my setup a third class setup. I would consider a phase perfect to be a second class setup, having real 3ph power would be first class. (I don't have a phase perfect but they sound great).
 
Well I know for a fact a VFD can run a cnc I know a handful of people that do it flawlessly on 220single phase they just have smaller machines than I have. The problem I have with rpc is the variable speeds you get with a cnc make it hard for it to keep up since it's constantly speeding up or slowing down. I know it won't draw the full 65 amps probably ever but I'd like to be overpowered in case it ever happened.

More likely your friends are running their spindle motor directly on a vfd, and the control is running the axis servos on 115 single phase.

I ran a 10hp cnc lathe on a 20hp rotary converter for years without trouble. I don't know why "constantly speeding up and slowing down" would be a problem, but my machine had constant surface speed and went up and down all the time. The rotary converter never blinked.

Highly doubt youre ever going to need to get close to full load amps in your garage....I bet you'll only flip the breaker if there's an electrical short or some other failure.
What feels to me like a heavy cut on that 10hp 18" lathe I've got only pulls 18 amps.
 
If you are asking for the "BEST" way, that is obviously a Phase Perfect, if you cannot get real 3 phase.

It is essentially a single section of a BIG VFD, passing through the two legs directly, and making the 3rd with the "section of a VFD". It just puts out straight 50 or 60 Hz, and will supply the start current etc for any motor within the ratings. It also passes return current, as from braking , etc.

It is NOT the cheapest solution, bit it IS a "no problem" solution.

As for the breaker size, that is somewhat deceptive. The Phase Perfect ("PP") probably uses the LEAST input current per output ampere of ANY of the solutions. It takes in current in the most efficient way, via a bidirectional power factor correction circuit. And it is around 95% or better basic efficiency.

The rating cited was almost certainly a rating based on supplying full output power, and possibly surge current for a load. It would surprise me if you could not operate it on a smaller breaker as long as you do not pull full power. The power factor correction means the PP should have hardly any "inrush" current when turned on.

An RPC will draw current to supply the "generated leg" at about 80% efficiency. That contrasts with the 95% or so of the PP. Then the motor also has to draw an "exciting current", which the PP has no equivalent to. That motor current is used to provide the magnetic field in the motor, and is drawn even if there is NO load on the RPC.

Overall, the PP should draw the least current, and provide the lightest load on the power lines per HP of supplied power.
 








 
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