To VFD or to not VFD

sdhorton

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Hi, thanks for letting me play, I have a South Bend 14" lathe with a 3 hp 3 ph motor with max amperage of 10.5 amps.
Like many others I need to power this from a 220 single source. I have looked at RFCs and SFC and FVDs until my head is spinning. Have any of you done this and can you make specific recommendations as to what power converter I should use and why? This lathe has a variable speed system in it, it is like a reeves drive, or like a snow machine clutch set up. That and a lube pump in the head need 110v AC that should come off the power source ONLY when the motor is turning or you will damage the vari-drive.
 
You could easily use a single phase to 3phase VFD and use it at 60Hz
The 3phase motor would work as intended, the reeves drive would be used for variable speed
You could ramp the acceleration and deceleration to your needs too

i put a 3hp 3 phase motor on my shenwai 1236. It greatly improved the performance

a RPC is easy to make but it would require a 5hp idler motor to operate efficiently

a static converter is even easier to construct, but you will not not develop the entire motor output . You’ll loose about 1/3 of the motor hp potential.
Most times this is not an issue with sparsely used equipment under light to moderately loaded operational conditions

the VFD is the best option for the price, but there is some knowledge to gain to setup if you are not used to control devices

here is my 3hp conversion on the shenwai 1236

 
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Listen to @Ulma Doctor !
Get the VFD!
A little search in this forum will find the most complete discussions, and explanations of the new technology that is hidden behind the little three-letter reference.
 
If you’re using a vfd, some have a relay contact that can be set to close on running which could be used for the lube pump, probably via a small contactor.
 
VFD for sure. I love having one. I have not heard of anyone regretting the decision to get one.
 
This lathe has a variable speed system in it, it is like a reeves drive, or like a snow machine clutch set up.
Since your lathe already has mechanically controlled variable speed, you might consider installing a Rotary Phase Convertor. That way you could power other three phase machine additions to your shop, but a VFD would likely be less expensive if you don't foresee any future need. I can say my RPC was one of my best shop investments ever. There's a lot of great three phase equipment available, usually for a fraction of the cost of single phase machines.

Best,
Kelly
 
What is wrong with using the VFD and the variable speed pully system to compliment each other and extend your speed envelope? My mill had a speed range of 120 to 2500. When I installed my VFD I left the multiple pulley system and when combined with the VFD gave me a speed range of 30 to 5000 rpm. As far as powering the lube motor my VFD had some extra contacts that I didn't use and if I remember correctly they were make and break contacts for running other accessories.
 
VFD for sure. I love having one. I have not heard of anyone regretting the decision to get one.
I won't call it a regret, but I took the VFD off my Bridgeport mill and went to an RPC and I like the setup better. I like being able to use the factory F/R switch, and the wiring for the light, DRO and power feeds comes off the step-down transformer, so it's a simpler setup. The bonus is the RPC is quieter than the VFD was...especially because I have the RPC 20ft away.

The cherry on top was that after I made the switch I added three more 3-phase machines and I didn't have to spend another $1K on decent VFDs.
 
There is a really nice North American Rotary 5hp RPC in the classified section here listed for $275....even with expensive shipping to you it would be less than the $500 they go for on Amazon. I have the 7.5hp version and it's really nicely made.
 
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