Phase convertors?

[Carl Beckett]

You are in the Hartford/Boston area. RPC's come up on CL from time to time, with a 10hp being about $500. Be patient and buy a used one and it resolves all your problems.

[Mitch schiffer]

I prefer vfds if you are just going to have 1 or 2 3 phase Machines. I have several 7.5hp vfds in my shop and I have been happy with them.

[William Hodge]

I have a 20 hp rotary phase converter I start with a nut driver in an electric drill. The drill gets the motor spinning at 1700 rpms, then I throw a big old knife switch to energize the motor. Removing the nut driver from the shaft before throwing the switch prevents having a 20 hp Dewalt electric drill flopping around in my hands.
Cost:
20 hp motor: probably a few hundred dollars
Big old knife switch: free
70 amp breaker in the main panel, conduit, 3 phase panel, and big ass wires: $500. for an electrician to install it, 20 years ago

[Maurice Mcmurry]

That boat builder on YouTube that my daughter thinks is sooo cute has a nifty pony motor, with some safety measures, for starting his.

[William Hodge]

That boat builder on YouTube that my daughter thinks is sooo cute has a nifty pony motor, with some safety measures, for starting his.

Do you have a link?
Hanging on to a jumping electric drill while I had cracked ribs was character building I didn't need.

[Michael Schuch]

I built my own 10hp balanced rotary phase convertor about 30 years ago. It uses capacitors to initially start the idler motor.

I really like being able to bring home a new 3ph machine, plug it into the phase convertor, have it fire up immediately and be ready to go. I did not run 3 phase wiring throughout my shop though so it is somewhat cumbersome to unplug one 3ph machine then plug in another one when using multiple machines in a project. So most of my 3 phase machines now have VFD's on them which is somewhat involved but it is nice to be able to plug them into any available 220v outlet.

[Maurice Mcmurry]

14:40 minutes in

[Maurice Mcmurry]

Dad has a giant phase convertor. It is capacitor start. It is on a 60 amp breaker. The junction / capacitor box is huge. It was made by the guy who kept the grain elevators, the Wonder Bread bakery, the grain driers on several thousand silos and grain bins, and lots of other stuff, working for 50 years or more. We sure do miss him. Which one of the three sons will get the phase convertor? I hope it is me.

[Kurt Wyberanec]

Spoke to someone at PP today and got some info....couple of quick questions.....

Why do I need an 80 amp breaker for a 10hp PP that only draws 30 amps? Am I missing something there?

2) Can one of you explain to me how I could make a VFD work for this machine? I guess I don't quite understand how it becomes a phase convertor so that I can run a 3p machine off my single power?

Thanks everyone!

[Bill Dufour]

One advantage of a VFd is it can be underrated. IOW a 5hp VFD can run a 7hp motor just fine. But that motor will only put out 5 hp. Any other type of converter must be big enough and be balanced to handle the motors full hp. This gives you options to buy a smaller VFD for now and latter buy a bigger, more expennsive, one and reuse the old one for a proper size motor. A vfd can also be derated and that same 5hp VFD can run a one hp motor when you buy the 7.5 hp vfd you really wanted but ahd to wait for a good price.
Bill D.

[Kevin Jenness]

2) Can one of you explain to me how I could make a VFD work for this machine? I guess I don't quite understand how it becomes a phase convertor so that I can run a 3p machine off my single power?

Here's an explanation of how it works https://vfds.com/blog/can-a-vfd-conv...o-three-phase/

You can't have any switching between the vfd and motor, so you have to bypass the machine's stock magnetic starter. If you have a separate scoring motor you will need two vfds. A vfd allows for controlling a number of factors like speed, ramp-up/down time, reversing, remote on/off switches and so on, which are overkill for a table saw.

A static phase converter is a simple economical alternative for an overpowered machine. I have a 3hp slot mortiser that has been running on a static converter for 30 years without problems. I would be hesitant to run a tablesaw on one, but if you were always cutting 3/4" material with a 10 hp saw, 2/3 of the rated power would still be more than enough.

As several people have said, a rotary converter allows for running multiple machines and does not have to be expensive. I use one for my slider and planer, while I have vfds on my lathe, edge sander and exhaust fan, all of which benefit from adjustable speed.

[Carl Beckett]

Here's an explanation of how it works https://vfds.com/blog/can-a-vfd-conv...o-three-phase/

You can't have any switching between the vfd and motor, so you have to bypass the machine's stock magnetic starter. If you have a separate scoring motor you will need two vfds. A vfd allows for controlling a number of factors like speed, ramp-up/down time, remote on/off switches and so on, which may be overkill for a table saw.

A static phase converter is a simple economical alternative for an overpowered machine. I have a 3hp slot mortiser that has been running on a static converter for 30 years without problems. I would be hesitant to run a tablesaw on one, but if you were always cutting 3/4" material with a 10 hp saw, 2/3 of the rated power would still be more than enough.

As several people have said, a rotary converter allows for running multiple machines and does not have to be expensive. I use one for my slider and planer, while I have vfds on my lathe, edge sander and exhaust fan, all of which benefit from adjustable speed.

This mirrors my experience. Even a static phase converter has a place, I ran a large belt sander off one for years with no problems at all. Variable speed via VFD can be nice for certain equipment. I wouldnt use it on a table saw nor a planer so that doesnt click for me. For me, once I have to start rewiring the base machine and using multiple VFDs to drive multiple motors on the same machine, it becomes more complex than I want (in part because I might want to sell the machine some day and DIY modified machines are always suspect). The RPC simply gives you 3 phase power to tap into and run whatever you want.

[roger wiegand]

VFDs don't play well with electronics, so if your plans include machines that incorporate electronic components that would drive a decision towards the RPC or PP. I installed an RPC from American Rotary and have been quite happy with it except for the irritating whine it makes-- the whole building seems to resonate with it. I'm wishing I'd bought the outdoor enclosure for it so I could get it out of the shop. OTOH, I do remember to turn it off when it's not in use!

[Maurice Mcmurry]

Dads roto-phase will run "Belching Beulah". The two drums each have very big motors. The oscillator and feed motor is a a bit smaller but also very big.

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[Phillip Mitchell]

Spoke to someone at PP today and got some info....couple of quick questions.....

Why do I need an 80 amp breaker for a 10hp PP that only draws 30 amps? Am I missing something there?

2) Can one of you explain to me how I could make a VFD work for this machine? I guess I don't quite understand how it becomes a phase convertor so that I can run a 3p machine off my single power?

Thanks everyone!

1) Typically it’s a 2:1 ratio, but each converter is slightly different and there may be a bit of CYA (cover your ass) factor in there and they have decided to up size to the nearest bigger breaker. Did you ask them why you need 80 amps single phase for 30 amps 3 phase? They would be able to tell you more directly than any of us, I suspect.

2) Several folks including myself have indicated that wiring in a VFD in your particular case is almost certainly more trouble / work / modification than its worth. You would do well to save a VFD for a smaller amp, less switch heavy, single motor machine that can benefit from speed control and external switching / controls.