Just picked up a 16" south bend lathe from the sixties and a B&S surface grinder for our shop and am having a difficult time picking a rotary 3 phase converter. I initially was going to order a phoenix 5hp unit seeing that our bridgeport is only 1hp, the lathe being a 3hp, and the surface grinder being a 1hp. While asking questions to the sales rep at phoenix he mentioned that 5hp would not be enough for the lathe and suggested a 7.5hp, is he trying to upsale me or will the 5hp be enough? We will only being using one machine at a time.
Rotary phase converter needs?
- Thread starter Rivet
- Start date
Does the lathe have a clutch or does it start up the motor with a load? If it dose not have a clutch a larger converter might be needed if your spinning up a heavy work piece. If not the 5hp should be ok.. That said just make your own converter all you need is a used 3 phase motor ( very cheap) and a few dollars more in capacitors and maybe a relay depending on the design... You should be able to put one together for under $100.
William...
William...
What is the top spindle speed on the South Bend? Being a clutchless machine, a high top spindle speed takes a lot of effort to start due to the inertia of the drive and spindle. I think the salesman is probably correct. I would follow his suggestion and go with a 7.5 HP converter. The only thing more expensive than an oversized converter is an undersized converter - you get to buy two converters then!
I start my 8,500lb 10HP American Pacemaker with a 10HP converter I built with an 1150 RPM motor and it starts fine. The Pacemaker is a clutched machine. I also run my Series II Bridgeport a 1HP Edlund High speed drill, and other machines on it. The Pacemaker comes up to speed in about 4 seconds, it seems.
I would buy or build more rotary converter than you currently need. You never know when another machine might come along which is bigger than your current machines.
I built my 10HP using the Fitch Williams design on Practical Machinist. His plans are in a sticky thread at the top of the "Phase Converters and VFD's" forum. The thread title is "Phase Converter Plans". My converter can be seen on the wall in a few photos in my bandsaw thread. They are not difficult to build if you understand basic electricity and industrial electric control. In fact, I learned a lot about 3-phase power and AC electricity building the project.
A few photos of mine:
The flexible conduit was a temporary "gotta see it run" setup.
In the not too distant future, I need to build a much larger converter. Probably 40-50HP. The design will be the same, just more capacitors!
You can get new soggy film capacitors, contactors, etc. from Surplus Center.com. I got almost everything from there. Only the Hoffman enclosure and Allen Bradley multi-purpose timer came from other sources. The motor was brand new, with the plastic and test report from Ebay. $200. Current retail price on the Reliance 10HP XT series 1150 RPM motor is $1,850. DON'T buy your motor from the factory. Buy it NOS!
I start my 8,500lb 10HP American Pacemaker with a 10HP converter I built with an 1150 RPM motor and it starts fine. The Pacemaker is a clutched machine. I also run my Series II Bridgeport a 1HP Edlund High speed drill, and other machines on it. The Pacemaker comes up to speed in about 4 seconds, it seems.
I would buy or build more rotary converter than you currently need. You never know when another machine might come along which is bigger than your current machines.
I built my 10HP using the Fitch Williams design on Practical Machinist. His plans are in a sticky thread at the top of the "Phase Converters and VFD's" forum. The thread title is "Phase Converter Plans". My converter can be seen on the wall in a few photos in my bandsaw thread. They are not difficult to build if you understand basic electricity and industrial electric control. In fact, I learned a lot about 3-phase power and AC electricity building the project.
A few photos of mine:
The flexible conduit was a temporary "gotta see it run" setup.
In the not too distant future, I need to build a much larger converter. Probably 40-50HP. The design will be the same, just more capacitors!
You can get new soggy film capacitors, contactors, etc. from Surplus Center.com. I got almost everything from there. Only the Hoffman enclosure and Allen Bradley multi-purpose timer came from other sources. The motor was brand new, with the plastic and test report from Ebay. $200. Current retail price on the Reliance 10HP XT series 1150 RPM motor is $1,850. DON'T buy your motor from the factory. Buy it NOS!
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The lathe does not have a clutch, and as far as actual speed I am unsure as there really isn't much information on the net on this particular lathe. The motor is rated at 1735rpm and it is an 8 speed lathe if that helps anyone that is more familiar.
VFD is looking like it may be a nice option but I think I may be a bit stuck on having a rotary to do single duty for all machines.
VFD is looking like it may be a nice option but I think I may be a bit stuck on having a rotary to do single duty for all machines.
rsanter
Well-known member
VFD all the way
it was the best add on to my mill I have done
bob
it was the best add on to my mill I have done
bob
After looking into it further, I think I found the most cost effective solution thanks to you guys (I appreciate it). Since we already have a 1hp rotary converter for the bridgeport, I can share it with the surface grinder so the only other machine I have to worry about is the lathe. For the lathe I found a 3hp VFD local from Dealers electric for $314 in a full wall mount enclosure or $214 without capped ends. With the vfd it seems like I can have a brake for the chuck and variable speed from the panel of the vfd. Sounds better than $600 for an imported 7.5hp rotary and $800 for a 3hp domestic name brand.
I'm running a 3hp 13" swing lathe on a 5hp rpc. No clutch on my machine either. It will start up the 10" 4 jaw chuck at 1000 rpm no problem. But, honestly in a home shop I think a VFD is nicer because they are quiet and don't waste power. With a rotary phase
converter, you have to listen to the motor run all the time and pay for the electricity to run it.
I have a friend that is running a vfd on a 16" South Bend. It's really nice on a South Bend because you are limited on speeds and changing speeds is a little slow. The VFD will add infinite speed adjustment an electric brake to the spindle that the south bend lacks.
I bought a rotary because I was told that I couldn't run a VFD on my two speed motor in my lathe. I've since figured out how to do it and I might be selling the rpc in trade for two VFDs.
converter, you have to listen to the motor run all the time and pay for the electricity to run it.
I have a friend that is running a vfd on a 16" South Bend. It's really nice on a South Bend because you are limited on speeds and changing speeds is a little slow. The VFD will add infinite speed adjustment an electric brake to the spindle that the south bend lacks.
I bought a rotary because I was told that I couldn't run a VFD on my two speed motor in my lathe. I've since figured out how to do it and I might be selling the rpc in trade for two VFDs.
Aceman
Well-known member
I've never installed a VFD on a single phase to run a 3 phase motor, but I've heard you need to size them at twice the capacity to do it. 1HP motor=2HP VFD. Just something to look into before you make a purchase. Another thing I'll mention is the smallest VFD we install is a 5HP, that's our standard, I'm not saying it's the way to go for your project but both my boss and the VFD salesman both agree that it helps with the longevity of the drive.
We use Allen Bradley Powerflex almost exclusively, they seem to be about the easiest to program from what I've seen.
We use Allen Bradley Powerflex almost exclusively, they seem to be about the easiest to program from what I've seen.
this is the way to go
all 3ph VFD's can be set-up to run 1 in, 3 out...
we do it when we have large motors and 3 ph is not available, ie, rural pump station...
just remember, for a 1 HP motor you need a 1.73 HP drive (for equivilent voltages)...so you'ld use a 2
base the VFD on the input current, not the out put...
Hitachi VFD's are as well. No need to oversize. But they're expensive. $250 range as I recally. Full-featured though.
I must admit, for a home shop with small machines, VFD's do provide increased options. I went the phase converter route because some of my current and expected future machines are in the 10HP+ range and the controls are all 3ph.
My converter doesn't draw much real power. Maybe 750W? Idle draw is 1.8A roughly, most of which is reactive current. I expect the 50Hp converter that's in the planning stage will draw a couple kilowatts. Still perfectly acceptable for what it is. I'll parallel in the 10HP for light loads.
tdkkart
Well-known member
VFD, no other choice IMO. I run my 1HP lathe and mill on a single VFD, just not at the same time, been working great for nearly 10 years.