Here's testing on the main box. Main shut-off. And how the single phase 2-pole lift is wired against the 30A breaker. The metal tube on the left goes to a standard 3-prong dryer plug for lift.

http://forums.pelicanparts.com/uploa...1729612684.jpg




http://forums.pelicanparts.com/uploa...1729612684.jpg




http://forums.pelicanparts.com/uploa...1729612684.jpg

Prior to pricing the motor from Atlas take a look at the existing motor contactor (relay) and see if it has a free electrical terminal, if not will also need a different contactor and overload protection.

You can order and install a generic 7.5hp motor but there are a few different frame types and sizes, and mounting specs between manufacturers can be different, so just need to measure carefully.

Thank you. I have sent an email to Atlas Copco. And will research the relay.

How is the single phase lift working?

If you are asking me about the single phase lift, just using two of the three phase wires will give voltage, the waveform being 120 deg vs 180 deg and not really opposite. Not sure what happens running a motor continuous on it, likely less power more heat would be a concern. I have not tried it, up here most 3 phase in industry is 575v so need a transformer to bring it down to 240v anyways.

If you also need single phase for the lift possibly a transformer is a better solution?

Hopefully I am wrong and you can just use the two phases of three to run your compressor with no issues, does not sound right though.

Is it possible that the 3 prong single phase dryer receptacle used to be a 3 phase receptacle, and when someone changed it to the single phase receptacle they reused the wiring and disconnected the white wire on both ends? The fact that you've got a 3 pole breaker and disconnect switch would seem to indicate that at some point in time it was feeding a 3 phase load. Is the existing 7-1/2HP single phase motor fed from this panel or somewhere else? What are the bottom two 3 pole breakers feeding? If you're getting a 3 phase motor, make sure that it can run on 208V. It would be specified something like this: 208-230/460/3/60.

Anything is possible. That said, I am 99% sure the white wire hadn't been crimped with the grub screw. It is in the pic because I had put it in. But I found out this switch box and outlet were feeding a large compressor years ago.

I used this box to "test" connect my compressor before putting it in place. I used the wiring I installed in my old shop to make an extension cord.

I have a single phase to 3 phase converter I got for my 3hp buffer. I wish I could make it go in reverse.

Mike, can you expand on how to get 240/1 out of this box?

breaker just arrived. Why the two clips on the back vs. the one for teh 30?


http://forums.pelicanparts.com/uploa...1729628039.jpg


http://forums.pelicanparts.com/uploa...1729628039.jpg

No!


I was mistaken...

ok thanks.

if there's a possible bright spot, the motor runs for only a few minutes at a time, 10+ times a day.

I'm waiting to hear back from Atlas.

Googling a little, I get stuff like this:

Yes you can run the 1-phase, 220V motor from a line-line connection on a 3-phase, 220V delta. You would still need the start capacitor. Also, make sure case grounding is properly maintained as applicable (detailed wiring drawing will show).

If you are asking if you can supply the start capacitor leg with one of the other line-line delta voltages (for out-of-phase voltage) IN PLACE of the start capacitor then you will have to ask the manufacturer. Using another line-line would provide a full ±120°
shift whereas using the start capacitor and the same line-line voltage would be something less (e.g. −90°<��<+90°).

Is the start capacitor something I can wire inline AFTER the buck boost transformer?

The single phase motor will already have the start capacitor.

This is worth watching: https://www.youtube.com/watch?v=r3hSaiIt8-Y

Thanks. I'm puzzled about him talking about seeing higher voltages, I was measuring 203-204V at the panel and at the switch box in the other room.

I have a 208V to 230V buck boost transformer.

So my question becomes, and I hope this scenario works:

I put in the new 60A breaker
The switch set up for the car lift uses only Black, Red and Green, white wasn't connected

Can I just use the Black and Red into my transformer in the same way or is there a different/better way to wire it?

Secondary to this, because I essentially made an extension cord out of my old wiring (metal clad), it's only grounded at the switch box. Is that ok?

In my old shop, white was neutral at the buss bar and center mounted to the outlet, green grounded at the box and to the metal box in the wall in the compressor room.

I greatly appreciate all the help on this. The last 6 weeks have truly been hellish and I'm not surprised at all about this latest twist. In fact I would be surprised if this hadn't happened.

With all the talk about car lift, air compressor, buffer, buck/boost transformer, phase converter, single phase, three phase, I've actually lost track of exactly what you're trying to do.

Sorry, I’m trying to connect my single phase air compressor into a 3 phase system.

Assuming your 7-1/2HP single phase motor is rated to run on 208V, you should be able to install a 60A 2-pole breaker (not sure why you got a 3-pole) and run a couple of #6 copper wires (not white) along with a #6/8/10 ground conductor (green). There should also be a 60A lockable disconnect switch at the compressor. If you are using metal conduit, that can serve as the grounding conductor and you wouldn't need the green wire. But, if you use flexible metal conduit or flexible non-metallic conduit between the disconnect and air compressor, that would need to use the green ground wire.

As you saw in the video, you can get 240v from 2 legs of residential power. I stupidly got in my head that they were two PHASES, but in fact they're two legs that are 180 out, not 2 phases that are 120 out. So, no 240V for you! :)


Well, except for using your existing transformer.

Honestly, your 208 to 240 transformer is kinda weird, when you could get (or build!) a single phase, 120V to 240V transformer that would probably be smaller and cheaper. a 120V to 240V single phase transformer is just a couple coils of wire, while the 208 2-phase to 240 1-phase probably needs some sort of rectifier circuit.



This is all coming from someone who had to cobble together all sorts of power feeds for all sorts of old, used, decrepit heavy machines from many countries, power standards and eras. NEVER take my electrical advice as code, or legal or safe, but it usually worked.

Thank you. I got the three wire because that's what was in the cabinet. I have to get stitches out this morning but will install the 3 pole breaker leaving the white out of the circuit, just for testing.

Thanks Mike. I got the 208-230 9 years ago for at my old single phase 208 shop.