Hooking up 3 phase rotary converter?

[Jason280]

I recently picked up a South Bend lathe and Induma milling machine, both of which are 3 phase. The individual I bought from had them both running off an American Rotary 3 phase converter, using individual cut off boxes to each machine. All of this, including the wiring, was included with the machines. I took a few pics of the wiring while disassembling, but unfortunately the pics aren't detailed enough for me to be comfortable enough just wiring everything back together.

I've checked the American rotary website, and haven't been able to find a model that uses a box similar to mine (likely an older model). Here is a somewhat decent pic of the box:

Opening the box, you have the capacitors(?) and post block in the middle for the ON/OFF switch wiring. On either side in the middle, you have 3 rows of terminal posts for wire connectors, and at the top, you have 2 rows. If I understand this correctly, the rows of 3 in the middle are for the 3 phase equipment, and the row of 2 at the top are for the 2 hot legs from single phase 240v (basically the input for powering the converter). There are also single posts on either side in the rear for ground hookup.

The idler motor, best I can remember, was wired to one side of the 3 row terminal posts. Each cut off box was wired from one side of the 3 terminal posts, and then run to each machine. The 240v single phase input had a hot leg going to each one of the posts on the top (on one side), and each one was grounded to separate posts on either side. Does this sound correct?

I'd like to have this hooked up today, but won't be able to call American Rotary until Tuesday. Thanks!

 

[alfredeneuman]

That box LOOKS an awful like a Static Converter. (Which is a single phase to 3 phase converter itself.) It's also a terribly inefficient way.

 

[930dreamer]

If you don't have a 3 phase idler motor its a static converter. Capacitors are usually start and run.

 

[oldgoaly]

Yes it is missing the idler motor or it is a static convertor

 

[Jason280]

There's an idler motor, just didn't take a pic...

 

[Jason280]

 

[BillK]

How about asking the guy you bought it all from ???

 

[930dreamer]

Looks like the incoming power L1-L2 go to the top two lugs, T1,T2,T3 go to the other 3 lugs but you have the same lugs on both sides so???

Black lug with 7 screws is for the yellow cord with red, white , black, green I don't see a brown wire?

The 3 # 6 wires with red tape look like your T1-3 lines to the idler motor, those would go to the bottom 3 lugs.

 

[Jason280]

The 7-post terminal block in the middle is simply for the ON/OFF switch from the front cover, its actually the easy part to wire up.

I also know where I need to wire in the 240v single phase input, it uses either side of the two post terminals at the very top. Its worth mentioning that each terminal bar runs/extends from one side to the other (you have continuity across each bar from one side to the other). It isn't as though there are 10 separate terminal bars on both sides, in reality its on 5 separate terminal locations...you have L1 & L2 a the top (for both sides), and T1 - T2 - T3 in the middle.

My biggest concern is whether there is any special way the T1-T2-T3 terminals have to be wired from the individual cutoff boxes and idler motor? I know that each cutoff box had each wire matched top to bottom (across the cutoff itself), using red - white - black wires (and green ground). I know where my line input goes to power the whole thing, and I know how to wire up the front panel switch, I'm just a little iffy on how I run 3-phase power out to my idler motor and individual machines.

Regardless, I'm shutdown until I can find a few 6ga ring terminals today...looks like I will have to call American Rotary either way.

 

[matt_i]

The sticker has it all.

The L1, L2 come from your single phase circuit panel.

The T1, T2, T3 feed both the idler motor AND any downstream wiring you are using for machines. You said the bus bars run thru or across and have continuity so if its more convenient, hook the idler motor to one side and the downstream wiring to the other.

The way I wired up my RPC back in the day was to have an EMT conduit setup with THHN conductors going to twistlock receptacles. All of the outlets are wired in parallel and thus they all go "hot" at the same time. Real ground wire connected all the way back home and not reliant on the EMT to do the job.

How you protect the downstream conductors is another issue, is the T1,T2,T3 output fused or breakered or is it designed to trip on the input side. Reason I ask is most machines will run from #10 AWG wiring but if you are feeding with #6s there's an inherent problem in the ampacity and where the protection for the #10s lie. Furthering, the knee mill is around a 2hp motor (? guessing here) which will draw less than 10A on 240vac.

 

[Jason280]

Honestly, I would have used smaller wire, but it came set up with lengths of wire already cut...I simply ran the 6 AWG to the 50a plug.

I ended up calling American Rotary, and they were able to walk me through it (as well as email me the correct wiring diagram/manual for my converter). The idler motor wiring is specific, but the instructions were easy enough to follow. One odd thing I noticed, the drum switch for the lathe operates opposite of how its marked. It has an "R" (left side) and "F" (right side) marked below the lever, but they are opposite to which ever one you select. I honestly can't remember if it was like this before I moved it, so it could le labeled incorrectly (or wired wrong).

Another interesting thing I noticed, I get 110ish volts at the T1 & T2 terminals, and 220ish volts at T3. I also checked amp draw on one of single phase legs inputs. With the idler motor going, it was drawing 3-4 amps (so around 6-8 amps total). The lathe was pulling around 6-6.5amps per side, and the mill was closer to 8 or 10. Of course, that includes the amp draw from the idler motor.

I will say this, if I ever have to replace either motor, they will be simply switched out to 240v single phase. The lathe motor is only rated at 1.5 HP, and the mill is 2HP. I *might* consider a VFD, but sub 3HP electric motors aren't all that expensive.

 

[alfredeneuman]

Do you plan on replacing those cords with conduit and wire?
They are a violation of the Code..

 

[matt_i]

One odd thing I noticed, the drum switch for the lathe operates opposite of how its marked. It has an "R" (left side) and "F" (right side) marked below the lever, but they are opposite to which ever one you select. I honestly can't remember if it was like this before I moved it, so it could be labeled incorrectly (or wired wrong).

So here's the thing about 3 phase power: You reverse any 2 of the 3 leads and the motor rotation reverses. So all you have to do on your lathe is find the input main wiring and reverse *any* two of the 3 poles and this issue will be fixed.

On your 110-120vac, is that T1 - GND or T1-T2...because you should have *roughly* 240vac from all T1-T2, T2-T3, and T1-T3.

 

[Jason280]

On your 110-120vac, is that T1 - GND or T1-T2...because you should have *roughly* 240vac from all T1-T2, T2-T3, and T1-T3.

That was to ground, I don't think I checked between individual phases....I'll have to try them again once I get back out into the shop.

 

[walta]

Before you call it good please take a moment and set your meter to ohms and be sure the case of your motor, idler, phase converter, disconnect and every part of the lathe all are connected to ground.

Walta

 

[DSMR]

The capacitors are there to provide a phase shift on your 240 line input. They are 180* degrees apart while true 3 phase is 120*. The generated leg will always be correct of course. Rotary converters are okay but far from idea. Just remember when you add a high impedance load (motor!), this will cause an imbalance.