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Machine Shop and Tool Talk

Phase converter

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Old 11-11-2015, 05:55:31 PM
Bob N Bob N is offline
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Default Re: Phase converter


I have used over the last 30 years VFD's, Static converters, and recently put in a rotary.

According to your post - a 3HP 3ph mill ( that is big one) limited use and what is the most practicable way to go.

Buy a static converter and be done with it. If you were planning a big shop with all kinds of 3ph stuff then you need to consider other options. Unless you like to tinker then go ahead and try and build a rotary, if just want to get rolling by a static.

Just get on line and find one that matches your mill, I strongly recommend you call the supplier and describe the motor ie HP and amps, so they can tell you which one is a best fit.

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Old 11-11-2015, 08:04:30 PM
ronm ronm is offline
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Default Re: Phase converter

I have to agree with Bob, that's what I did when I got my mill. Bought a static on ebay, wired it up & I was in business...I've had it at least 10 years, & no problems.The motor has had enough power for anything I've done, end mills, flycutters, & up to about 1-1/4" drills.
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Old 11-12-2015, 01:43:35 PM
Steve Webre Steve Webre is offline
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Default Re: Phase converter

Hey Toesmack,

Have a GENTEC RPC powering a lathe in the shop for the last 8 years or so. Went the RPC route because a large used mill was (and still is) in the long term plan and it will likely be 3 phase. The RPC was a bit pricey compared to static or homebrew, but has been completely hassle free to date with lots of hours. Mounted it on the back of the lathe and re-wired an existing button on the lathe to start it. Would do it again w/o hesitation. Good luck!
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Old 12-13-2015, 07:15:15 PM
prybar prybar is offline
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Default Re: Phase converter

FYI, in 1991 I bought a new Victor 16-40 lathe 7 1/2 hp motor. This is when I started in the garage. They gave me a free static converter. Lathe would just hum, they sent me two more, even bigger. Still would not work. Electrician wash stumped.
Notified the seller, they called the manufacturer, they called the engineer. They decided that because the cast iron they used was produced with negative ions, it would not accept a static phase. They sent me a 15 hp phaseamatic rotary. Lathe has been perfect since.
I can run 4 vertical mills, 3 horizontal, one lathe, cold saw and drill press at the same time. 100% power with a stabilizer for the cnc.
Phaseamatic rotary converters produce 3 time there rated hp. Example: my 15 hp converter will run 45 hp worth the motors. Like15 three hp 3ph motors at the same time.
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Old 12-18-2015, 11:33:55 PM
JLeatherman JLeatherman is offline
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Default Re: Phase converter

VFD's are great if you are pretty sure you'll only have one or two machines, and you want/need the variable speed option. I put a VFD on my first mill and my first lathe, and loved it. But then I got another mill, and another lathe, and a 3-phase grinder, and a 3-phase vertical bandsaw, and... It's real easy to switch a RPC from machine to machine (or in my new shop I just wired one up to multiple outlets). A VFD is not easy to move from one machine to the next because the parameters have to be configured properly and typically they're hardwired to prevent accidentally unplugging it from the machine while powered (which will instantly fry the VFD). They have their place, I still have one on my Bridgeport mill because I like having additional speeds in between the belt steps. If the mill is all you're buying, and it isn't already a vari-speed, a VFD is a good choice. If you think you'll get more equipment later, or the mill is already a vari-speed and you don't need to vary the VFD, I'd get or build a RPC.

By "solid state" if you mean a static phase converter then those aren't great. They only use the third leg to start the motor, and then it runs at 2/3's power. Unless the mill was overpowered to start with you'll miss that extra 1/3'd, and some people claim the surface finish suffers because the motor isn't running smoothly. It's fine for a drill press or grinder, but not a mill.
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