VFD for return to 3ph?

[PixMan]

In my shop I use a "recycled" 15HP 3-phase motor, no idler/starter motor, ropes or pulleys required. I know next to nothing about this, so I had bought the capacitor-equipped "box" from American Rotary for $350 and the motor was free. All I know is that it's noisy, but works flawlessly to power up a 5HP lathe, 2HP mill and 2HP surface grinder.

I don't get the variable speed out of it as you would a VFD, but I have had both the lathe and mill running at the same time with no issues. I consider moving it outside the shop, but the noise is less than an air compressor and I never forget to shut it off. In my dreams I'd get to use the 3-phase power on the poles outside the shop, but I'm probably moving the shop to my home in a year or two. Given that I have a tenant just above the shop, I'll have to get a Phase Perfect digital phase converter.

Given the situation with the OP in having various machines, I'd also suggest a suitable RPC. You can build one cheaper than the $350 I spent if you look around the internet for plans. You don't need mechanical start pulleys or pony motors if you use the right start capacitors.

[stevec]

Sunset, just as an aside, does the mill now powered with a 1 ph motor perform as well as it did with the original 3 ph one.?
By perform I mean smooth cutting and good finish?
Of course it's possible you, like I, probably never ran it under 3ph power.

[Sunset Machine]

I've never ran this mill under 3-phase, but I've ran others. I also deal with a lot of machined parts where I work. No difference that I can see, and I do look. A few years back I converted a surface grinder to single phase and it works fine too, feeling certain that (for me) converting it back to 3 phase would be a waste of time.

The big attraction for a homemade RPC is to not have to buy big single phase motors or VFD's.

[Mayhem]

I'm so glad that I have 3 phase power

[LJP]

I have run both static and rotary phase converters for at least 20 years. They both work without problems. I have run the very same machinery (woodworking machinery 2.5 to 7.5 hp) on true 3 phase power. There is a difference, I can hear it on start up. True three phase has a "quicker, more energetic" start. And I do believe you can "feel" less horsepower with a phase converter. But once that motor is spinning, the machine does what it is intended to do.

I recently "acquired" a VFD and tried it out on a 20" woodcutting Powermatic bandsaw, hoping to be able to use it occasionally for metal work. It seemed to work fine as well. It is not hooked up yet.

The same source offered me a variable speed, 3 hp dc motor (runs off 110 ac) that I am thinking of putting on a SB13 lathe. He assures me that there is plenty of low rpm tork, and I will probably get higher rpm's than I get now with the original 2hp 3ph motor. My only concern with that is whether the bearings are designed to handle higher rpm's on the lathe? But, the high rpm's would only get very occasional use I would think.

Many options to run 3 phase machinery these days.

Larry

[f350ca]

(10-23-2013, 06:57 AM)stevec Wrote: Sunset, just as an aside, does the mill now powered with a 1 ph motor perform as well as it did with the original 3 ph one.?
By perform I mean smooth cutting and good finish?
Of course it's possible you, like I, probably never ran it under 3ph power.

I've heard this mentioned before but have a hard time imagining you can see the difference in finish.
If its a 4 pole motor you get 4 smooth sinusoidal pulls during each revolution on single phase vs 12 on 3 phase. Its not a pulse its a building and falling magnetic field. if the motor was at stall speed maybe you'd feel the rising and falling torque but at running speed the rotating inertia of the armature and associated load would have to mask the source. When your driving down the highway at cruising speed some new engines cut out cylinders for economy, does the ride get jerky?
I thought the advantage of 3 phase motors was physical size, instant reversing and no effect when numerous starts were required.

[stevec]

Well I guess it's a moot point for me now.
I tried to place an order today for one of these. VFD drive.
After an excruciating hour or so online I got to the payment point and the seller said my Visa would not authorize payment.
It's my "low limit/online use" card and I guess the bank/CC guys were trying to impress me with their diligence in refusing a precedent charge from the eastern block.
I declined to try my other high limit, closely guarded card ,so the deal will self cancel in 30 days.
It's encouraging to hear your opinions of the lack of difference in performance/finish condition from 1ph to 3ph.
Guess I just saved myself 350 bucks.
Thanks for all your input.