3 phase converter help

So with a VFD I cant use the forward and reverse switch?

Maybe it is covered in the other links presented but I will try to provide a quick answer here.

Again, in my opinion ...

You can reverse the direction of a 3ph motor by simply switching the two wires that go to any one of the three windings. That is what the drum switch does.

Lets think about connecting a VFD but skip the drum switch, just wire it directly to the 3ph motor as directed. Turn the VFD on and the motor turns in A direction. If it is 'backwards' just physically switch the wires going from the VFD to the motor. Now everything is going in the right direction.

Now the beauty of the VFD ... from now on, to get reverse just tell the computer inside the VFD to 'electronically' switch the wires [actually it switches the relationship of the phases but the end result is the same] by pushing a button on the front panel of the VFD.

You will not lose the ability to run the motor in reverse, you would just not use the drum switch to control the direction. You would use the buttons on the front of the VFD. Note that the VFD doesn't care much about which direction they are going so most of the features available in 'forward' are also available in 'reverse' ... variable speed, etc.
 
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I may never end up with another 3phase machine so I was thinking I could probably get around $50 for my converter so Id have about $50 in VFD. But Im worried about it holding up with these moisture problems being my lathe isnt in a heated shop. Looking at it that way I may be better going the electric motor route like you did. Maybe next time Im at the scrap yard ill ask if they will sell motors they have.

from your first letter till now it sounds like you know what to do. if your worried about 50 dollars you might be in trouble
 
from your first letter till now it sounds like you know what to do. if your worried about 50 dollars you might be in trouble

Just doing some math, a $50 VFD is a cheap route to go vs building a rotary converter. But a rotary converter will probably last me until I die. Im not sure how well electronics will hold up out there.
 
Just doing some math, a $50 VFD is a cheap route to go vs building a rotary converter. But a rotary converter will probably last me until I die. Im not sure how well electronics will hold up out there.

how do you BUILD a rotary converter ? its just a 3 phase motor already built, all you have to do is wire it. you'll have to wire a vfd too
 
So yes, you do not use the old drum switch but you do not lose the ability to run the motor in reverse.


That is a very mis-leading to those who are trying to figure all this out. You can keep the drum switch to start, stop and reverse the motor, you just need to rewire it so it will now control the VFD rather than the high voltage side of the motor.
 
That is a very mis-leading to those who are trying to figure all this out. You can keep the drum switch to start, stop and reverse the motor, you just need to rewire it so it will now control the VFD rather than the high voltage side of the motor.

I agree that the sentence was not well formed. I have edited the post to "You will not lose the ability to run the motor in reverse, you would just not use the drum switch to control the direction. You would use the buttons on the front of the VFD."

I thought I would suggest the simple implementation first ... eliminate the drum switch completely and just use the buttons on the front of the VFD.

After that implementation was up and running one could move on to figuring out the configuration of the drum switch ... what contacts are SPST, DPDT, momentary, etc. ... and what setting and options would need to be defined on the VFD to allow the drum switch to be used with the "Intelligent Input Terminals" ... at least that is what Hitachi calls them ... and then wiring it all up.

Or am I missing some other configuration utilizing the drum switch that you envision?

Arvid
 
how do you BUILD a rotary converter ? its just a 3 phase motor already built, all you have to do is wire it. you'll have to wire a vfd too

From what Im gathering a rotary converter just uses a 3phase motor and a static converter to start it. Once the motor is running it acts as a generator for the 3rd leg thats missing on single phase power.

That is a very mis-leading to those who are trying to figure all this out. You can keep the drum switch to start, stop and reverse the motor, you just need to rewire it so it will now control the VFD rather than the high voltage side of the motor.

I agree that the sentence was not well formed. I have edited the post to "You will not lose the ability to run the motor in reverse, you would just not use the drum switch to control the direction. You would use the buttons on the front of the VFD."

I thought I would suggest the simple implementation first ... eliminate the drum switch completely and just use the buttons on the front of the VFD.

After that implementation was up and running one could move on to figuring out the configuration of the drum switch ... what contacts are SPST, DPDT, momentary, etc. ... and what setting and options would need to be defined on the VFD to allow the drum switch to be used with the "Intelligent Input Terminals" ... at least that is what Hitachi calls them ... and then wiring it all up.

Or am I missing some other configuration utilizing the drum switch that you envision?

Arvid

I understand it now, you just need to tell the VFD what to do through a remote. I bought a millermatic 200 wire welder that didn't work. I got it home and tore it apart to find it caught on fire inside. It kinda worked the same way, used 24v dc for the remote to turn on the 115V wire spool motor and open the solenoid valve for the gas. Also to let welding current through.
 
My Dad told me when he opened his shop in NE MPLS back in 1955, that area did not have 3 phase power and the power company showed him how to make a phase converter. He said a few years later they brought in 3 phase to the area and he never hooked up, just used his home made phase converter.

Several years later at our cabin, we had a small shop and he made up another one.
Here is how he hooked it up.
He told me a simple formula for motor size is HP x 1 1/2: If you have a 5 HP machine 3 /ph. Buy a 7 1/2 HP 3 phase motor and

Connect wire numbers 4,5,6 together and wrap with tape.
Connect 1 phase power from your electrical switch to the 3/ph motor to wires 1 and 7 and your 3 phase machine, tape up,
Connect the other 1 phase wire from your electrical switch to the 3 / ph motor to wires 2 and 8 and another 3 phase to your machine. Tape up.
Connect the 3 /ph motor wires 3 and 9 to the last 3 phase to your machine.

He had a pulley on the motor shaft and used an old lawn mower rope to spin the motor and flip on the single phase power at the same time and away it went.

I have seen guys connect a 110 volt motor on the 3 phase motor to start it spinning and after it started to spin they would shut off the 110 motor and it would spin free, I guess there are a few other ways to do it too. But that's how you can hook it up.
 
Just a couple of points on RPConverters. They are not usually considered feasible for welders or plasma cutters because of the high current requirements of that type of equipment. I have also noticed that when my hoist has a full load hanging it sometimes don't want to start with the RPC running. When this happens I just start my lathe thus adding another motor/generator to the circuit and the hoist will start every time.
 
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