Question about hardware for installing a rotary phase converter in shop

[tominboise]

I have a rotary phase converter and a lathe with a 3hp 3 phase motor. My question(s) are regarding how to do the physical installation of the wiring. Namely, I will have the single phase ( 2 lines L1 & L2) going to the RPC and 3 lines coming from the RPC to the lathe (L1, L2 and T3). T3 is the generated leg.

I would like to have a magnetic switch feeding the RPC (in case the power drops out, I want the switch to open and cut the circuit to the RPC and lathe). L1 and L2 go to the RPC and also to the lathe itself. Do I connect L1 and L2 to one side of the switch, then on the other side, bring a short lead and connect two wires - one L1 to the RPC and the other L1 to the lathe? (Same with L2, of course)? Suggestions on the switch?

If so, is there a box available with buss bars? Or use wire nuts?

The circuit also needs a 30A breaker between the RPC and the lathe, to protect the RPC. Is there a single breaker panel box available for something like this? The feed to the RPC will be on a 40A breaker from the sub panel in the garage.

 

[LopezBart]

I would like to have a magnetic switch feeding the RPC (in case the power drops out, I want the switch to open and cut the circuit to the RPC and lathe). L1 and L2 go to the RPC and also to the lathe itself. Do I connect L1 and L2 to one side of the switch, then on the other side, bring a short lead and connect two wires - one L1 to the RPC and the other L1 to the lathe? (Same with L2, of course)? Suggestions on the switch?

I'd consider a 3 pole contactor, set up as a latching relay (hence the third set of contacts). MC button to start and latch the contactor closed, MC to shutdown. Use a 240V coil contactor so if you lose either leg coming in, it shuts down. The other two contacts take power to the RPC, of course.

This should go in an enclosure, of course; you can mount the on-off buttons on the cover.

The circuit also needs a 30A breaker between the RPC and the lathe, to protect the RPC. Is there a single breaker panel box available for something like this? The feed to the RPC will be on a 40A breaker from the sub panel in the garage.

Look for a Square D Qo2l30scp 30A - that looks like what you need, and can be mounted right next to the lathe.

Caveat - I'm not an electrician.

 

[tool_scrounge]

I found the set up recommended by “convert a phase “ company was pretty simple.

I have seen a 3 phase contactor added for connecting all three phases and the contactor was controlled by a square-d phase monitor purchased for pretty cheap on EBay. If any phase was too far out of spec it disconnected the load.

 

[cannuck]

look around the interwebs and you will find a LOT of designs for RPCs. Most will have capacitors bridging each leg to correct phase angles thus effective voltage of L1 and L2 vs. generated L3. You will also need another capacitor circuit to make the 3ph motor start on single phase. I built one this spring using a 5HP 3 ph 208/220 v. motor to feed a 3HP circuit using a momentary push/hold start button to kick the motor on, indicator lights to verify the 3rd leg was energized and pull in circuit to protect from re-energizing after power interruption. I used primary protection as the 230V single phase 30A breaker in the panel and 3ph protection with fused terminals on the 3ph final output. I think if you search GJ you might find a few such threads.

 

[tominboise]

I found the set up recommended by “convert a phase “ company was pretty simple.

I have seen a 3 phase contactor added for connecting all three phases and the contactor was controlled by a square-d phase monitor purchased for pretty cheap on EBay. If any phase was too far out of spec it disconnected the load.

This is a great schematic, thank you. If I could find such a disconnect switch that used a magnetic switch instead of the lever on the side, that would be ideal.

 

[tominboise]

look around the interwebs and you will find a LOT of designs for RPCs. Most will have capacitors bridging each leg to correct phase angles thus effective voltage of L1 and L2 vs. generated L3. You will also need another capacitor circuit to make the 3ph motor start on single phase. I built one this spring using a 5HP 3 ph 208/220 v. motor to feed a 3HP circuit using a momentary push/hold start button to kick the motor on, indicator lights to verify the 3rd leg was energized and pull in circuit to protect from re-energizing after power interruption. I used primary protection as the 230V single phase 30A breaker in the panel and 3ph protection with fused terminals on the 3ph final output. I think if you search GJ you might find a few such threads.

Thanks, I already have the RPC and have motored it from my single phase supply to make sure it was functional.

 

[nadogail]

This is a great schematic, thank you. If I could find such a disconnect switch that used a magnetic switch instead of the lever on the side, that would be ideal.

Sometimes "Less Than Ideal" is plenty good enough.

 

[My Old Tools]

First get a small 3 phase breaker panel. Run the RPC to it, then distribute to your equipment. That way when acquire a mill or other 3 phase equipment, your ready.

 

[wyliesdiesels]

This is a great schematic, thank you. If I could find such a disconnect switch that used a magnetic switch instead of the lever on the side, that would be ideal.

youre mixing up different things.

The item with the handle is a disconnect NOT a magnetic switch. a magnetic switch should not be used in place of a disconnect. you should use both. the disconnect is used for servicing especially if the panel is not within sight of and further than 50' away from the RPC

 

[tominboise]

youre mixing up different things.

The item with the handle is a disconnect NOT a magnetic switch. a magnetic switch should not be used in place of a disconnect. you should use both. the disconnect is used for servicing especially if the panel is not within sight of and further than 50' away from the RPC

Ok, makes sense. Thanks for clearing that up.

 

[tominboise]

Also, I think I will build a short stand to get the RPC up off the floor. It will be next to the lathe (I may move it outside in a weatherproof shelter if required due to noise). Does in matter if the stand is wood or steel? Or how high off the floor? I think it should be up some to stay out of the dust and dirt somewhat.

 

[larry_g]

Also, I think I will build a short stand to get the RPC up off the floor. It will be next to the lathe (I may move it outside in a weatherproof shelter if required due to noise). Does in matter if the stand is wood or steel? Or how high off the floor? I think it should be up some to stay out of the dust and dirt somewhat.

Depends if your convertor is an open framed motor or TEFC. Mine is enclosed and I have it screwed to a 2X that sits in a section of thick carpet pad to isolate the noise from the floor. The carpet pad reduced the noise transmission a lot. I have a split shop where I was able to put the RPC motor on the side opposite the machine area removing it from the machine area. If your using an opened framed motor then it makes sense to keep it in a cleaner area.

lg
no neat sig line

 

[tominboise]

This is the RPC

 

[wyliesdiesels]

ummm is that speaker wire coming out of that junction box?

 

[tominboise]

ummm is that speaker wire coming out of that junction box?

No, lamp cord, actually. I believe it went to a light that illuminated when the RPC was energized. It's no longer in the circuit, lol....