RPC and Mill Pictures

[Hacker]

Hello,
After trolling this site for awhile I thought I would show what I have been up to. Last summer I toke a chance and purchased a basket case Fritz Werner mill. Over the last six months a machinist friend and I have gone over it and checked it out and cleaned it. When we could not find any major mechanical issues with it other then the rapid traverse motor was missing (and still is) I decided to build a rotary phase converter (RPC) and a 240 to 440V transformer to get it running. Once I had the crude RPC running to supply power to the motor I found that the previous owner have made some changes to the wiring and bypassed the brake, reversing switch and the start switch. Decided that it was easier to tear it all out and rewire it and add stop and start switches closer to the operating controls. I then finished the RPC and fine tuned it. Everything now works on the mill but there are a few issues to resolve and whether to put the rapid traverse motor in. I want to use the mill for awhile and then decide if the machine is worth putting more money and time into it. Doubt that I will give this a full restoration just try and get that awful paint job off it and leave it at that. I have attached a few pictures of the milling and the RPC .

 

[kevin.decelles]

what is in the grey box on the floor to the right of the file cabinet?

 

[Hacker]

That is the 240/440V setup transformer

 

[Tom Kitta]

Neat power readers I have to add these from Aliexpress to my setup.

 

[Hacker]

They are actually very accurate, which was a bit of a surprise. Hopefully they last.

 

[Proxule]

Nice balanced leg voltages, I went down the RPC route too many years ago, But found VFDs cheaper faster and more practical.
Thanks for sharing!

 

[Hacker]

Thanks,

I would have gone the VFD route if I didn't need 440V in the shop.

I have actually fine tuned the voltage on RPC and it is less then 5% when the mill is running.

 

[Tom Kitta]

I went VFD route, realized its a mistake, got RPC and I am very happy. Once you have multiple machines RPC works soooo much better then VFD. I would still use VFD but not for 3ph but just speed control i.e. with 3ph input.

RPC IMHO is much more practical choice then VFD with multiple machines. Also you can run machines with multiple motors, you can run welders, you can change voltages etc.

 

[Susquatch]

I am up to 3 VFDs now and still happy. Planning another one for my lathe when I find the right motor. Love the variable speed. Love having everything plug and play. No regrets.

 

[Proxule]

I went VFD route, realized its a mistake, got RPC and I am very happy. Once you have multiple machines RPC works soooo much better then VFD. I would still use VFD but not for 3ph but just speed control i.e. with 3ph input.

RPC IMHO is much more practical choice then VFD with multiple machines. Also you can run machines with multiple motors, you can run welders, you can change voltages etc.

To some degree yes I agree, But there is a reason the industrial and commerical factories run VFD's
Biggest reasons is that you can adjust output speed on the fly, Adjust Tq curves and program the VFD to a specific motor to provide low end Tq and other misc goodies a RPC cannot.
Not to mention you have to balance an RPC to a specific load on each leg to be with in X % of amperage / voltage.
I am sure commercial RPCs can compensate on the fly, By a semi fancy vector VFD from good old china will run you 300$ shipped. Not so much for a commercial RPC

Just my 2 cents.

 

[Proxule]

Thanks,

I would have gone the VFD route if I didn't need 440V in the shop.

I have actually fine tuned the voltage on RPC and it is less then 5% when the mill is running.

Surprised you are unable to run that 440v motor on 220v. Most but not all 3 phase 440s I been near were able to run on 220.
What a shame.

 

[Tom Kitta]

To some degree yes I agree, But there is a reason the industrial and commerical factories run VFD's
Biggest reasons is that you can adjust output speed on the fly, Adjust Tq curves and program the VFD to a specific motor to provide low end Tq and other misc goodies a RPC cannot.
Not to mention you have to balance an RPC to a specific load on each leg to be with in X % of amperage / voltage.
I am sure commercial RPCs can compensate on the fly, By a semi fancy vector VFD from good old china will run you 300$ shipped. Not so much for a commercial RPC

Just my 2 cents.

Also most factories have normal 3ph input and do not need to change from 1ph to 3ph. I would not mind using a VFD in the same way - i.e. 3ph to 3ph. I have no problems connecting VFD to RPC.

You do not need to balance RPC at all - being within 10% is good enough. This is for voltage, not sure about what do you mean by amps. You can build in a circuit that would automatically add or remove capacitance to adjust for voltage.

I guess you could also add VFD to fix some output issues.

Bottom line is RPC is so much easier to use then VFD. Its not even close. With RPC, you get new 3ph machine. You bring it home. You plug it into the wall and just like that it works. With VFD you have to, buy an VFD (300 adds up quick) then you have to connect the VFD to the machine, then you have to figure out how to make the VFD be nicely enclosed, then you have to deal with what do I do with resistive loads & what do I do with multiple motors. And finally, with VFD you have to wait for the machine to spin up to speed - vs. RPC, its full speed after fraction of a second.

With 15 motors in the shop a 300 VFD would add up to a whopping $4500 not to mention wiring issues I discussed above. And an RPC will run you like $500.

Finally there is the freedom of being able to change voltages, run resistive loads. Its like if you had native 3ph in the wall.

I strongly suggest anyone serious about this hobby should use RPC. If you want VFDs - you can just add them after RPC output for speed control.

 

[Tom Kitta]

Surprised you are unable to run that 440v motor on 220v. Most but not all 3 phase 440s I been near were able to run on 220.
What a shame.

I run into multiple motors that were 460v only (or 440v or 480v) I have my surface grinder running on 460v as motors are re-wired 600v motors and only support single voltage.

 

[DPittman]

Isn't there supposed to be some sort of energy saving with the start up of motors using a vfd? I thought I read something about that somewhere but I could be out to lunch also.

 

[Tom Kitta]

Isn't there supposed to be some sort of energy saving with the start up of motors using a vfd? I thought I read something about that somewhere but I could be out to lunch also.

There is a soft start switch or you can use a VFD to use as soft start - but this is beyond most hobby shop motor sizes.

You can also use Delta - Y switch.

Its not to hit power company with a huge spike load. No savings in energy.

RPC will waste energy continuously but so do VFDs. I guess you need many VFDs on to equal an RPC. But under heavy load RPC will be getting more efficient while VFD less...

 

[Hacker]

Surprised you are unable to run that 440v motor on 220v. Most but not all 3 phase 440s I been near were able to run on 220.
What a shame.

It is actually 380V that I am running, I just used the 440V as that is what most people recognize. The motor housing on the mill is fitted to the mill and I would have had to get it rewound to work on 220.

 

[Hacker]

Also most factories have normal 3ph input and do not need to change from 1ph to 3ph. I would not mind using a VFD in the same way - i.e. 3ph to 3ph. I have no problems connecting VFD to RPC.

You do not need to balance RPC at all - being within 10% is good enough. This is for voltage, not sure about what do you mean by amps. You can build in a circuit that would automatically add or remove capacitance to adjust for voltage.

I guess you could also add VFD to fix some output issues.

Bottom line is RPC is so much easier to use then VFD. Its not even close. With RPC, you get new 3ph machine. You bring it home. You plug it into the wall and just like that it works. With VFD you have to, buy an VFD (300 adds up quick) then you have to connect the VFD to the machine, then you have to figure out how to make the VFD be nicely enclosed, then you have to deal with what do I do with resistive loads & what do I do with multiple motors. And finally, with VFD you have to wait for the machine to spin up to speed - vs. RPC, its full speed after fraction of a second.

With 15 motors in the shop a 300 VFD would add up to a whopping $4500 not to mention wiring issues I discussed above. And an RPC will run you like $500.

Finally there is the freedom of being able to change voltages, run resistive loads. Its like if you had native 3ph in the wall.

I strongly suggest anyone serious about this hobby should use RPC. If you want VFDs - you can just add them after RPC output for speed control.

Agreed that for 5 HP motors and larger as well as where multiple voltages the RPC is probably the cheapest way to go. Also if you built the RPC yourself then it is also going to be cheaper and easier to repair when something fails.

If you are running smaller machines where the motors can be easily changed to a common voltage go with the VFD and and run it on a designated circuit. Most small home shops you will be running one machine at a time. If your size the VFD correctly you can get away with running two motors at a time. I did this on my lathe where the tracer motor and coolant pump are connected to one VFD and I can run them at the same time.

 

[Susquatch]

If your size the VFD correctly you can get away with running two motors at a time. I did this on my lathe where the tracer motor and coolant pump are connected to one VFD and I can run them at the same time.

This is new info to me. Normally, the VFD senses the current flow in the motor winding and uses that as feedback to provide better output control. Two motors would confuse the bejezzus out of it.

Was there a VFD setting you used (ie something like ignore feedback and brute force the output) to make that work?

 

[Former Member]

This is new info to me. Normally, the VFD senses the current flow in the motor winding and uses that as feedback to provide better output control. Two motors would confuse the bejezzus out of it.

Was there a VFD setting you used (ie something like ignore feedback and brute force the output) to make that work?

I am with you on that one, I wouldn't do that or recommend it, it's just asking for serious trouble.

With the cost of VFD's (good quality budget ones that some of our members use) you are far better off as each can duty sized for the motors in question, along with optimizing performance for each machine.

 

[Tom Kitta]

Agreed that for 5 HP motors and larger as well as where multiple voltages the RPC is probably the cheapest way to go. Also if you built the RPC yourself then it is also going to be cheaper and easier to repair when something fails.

If you are running smaller machines where the motors can be easily changed to a common voltage go with the VFD and and run it on a designated circuit. Most small home shops you will be running one machine at a time. If your size the VFD correctly you can get away with running two motors at a time. I did this on my lathe where the tracer motor and coolant pump are connected to one VFD and I can run them at the same time.

When I said more then one motor I did not mean a coolant motor but similar sized 2nd motor. Say my surface grinder has 2hp for grinder and 1hp for the table. Or my drill press has 2hp for the drill and 1hp for the arm.

If you are using single VFD you would need to size it to the largest motor you are starting in your setup. Some pp have VFD on a little cart, plug one end into 240v 1ph, the other end to a machine they are running. Maybe some vfds have quick "memory" option for a different motor setup.

Using more then one machine is quite common. I use up to 3, mill, lathe and saw. But usually just two. This is why one has "power feed".

Switching motors, even when smaller, say 2hp to common voltage may not be "cheap" or may not be easy.