how do they get single phase from three phase?

[ericm]

The place we just bought has a large irrigation pump that's run off a dedicated 480 3phase. There's an electric gate which I'm pretty sure is run off the same meter. The docs for the gate operator say that it can run on 120 or 240v single phase.

My question is how do they normally get single 120/240 single phase from 480 three phase and does it matter for the three phase equipment?

 

[LXCam]

Tap two legs of the 480 and use a single phase transformer to step it down to 120/240.

Assuming it is feed from that and you have a 1/2hp drive motor you’d only need a little 1.5kva transformer. So if you see something like that, well there ya have it.

 

[LXCam]

Btw, if they are doing that you’re going to have either a 480v breaker panel or a fused disconnect feeding the transformer, then either a breaker or fused disconnect before the gate operator. Point being, they’ll be some equipment upstream that stands out.

 

[micromind]

The only way to get either 120 or 240 from 480 is a transformer. It can be either single or 3 phase, depending on the 120/240 needs.

 

[rlitman]

Tap two legs of the 480 and use a single phase transformer to step it down to 120/240.

That's one option, if there's a 3 phase panel to take from, and probably the better one. If you ONLY need 240V and don't need a neutral, and the service is 277/480 wye, you can also tap that single phase with a buck transformer (or reverse feed a boost transformer; they're the same thing). The advantage to this, is that buck/boost autotransformers are WAY smaller than step up/down transformers.

 

[ericm]

Btw, if they are doing that you’re going to have either a 480v breaker panel or a fused disconnect feeding the transformer, then either a breaker or fused disconnect before the gate operator. Point being, they’ll be some equipment upstream that stands out.

There's a couple electric boxes that aren't the usual homeowner stuff I'd recognize. One has a switch for the pump. The other is large, maybe 2' tall, with a big rotary switch knob and a small round push button labeled "reset". Next time I'm there I'll open it. There's a lot of what I'll charitably call farm wiring on this place so it might not have breakers/fuses in all the right places.

The meter showed something was drawing 0.009 kW. Since the pump wasn't on, that must be the transformer?

 

[wyliesdiesels]

The place we just bought has a large irrigation pump that's run off a dedicated 480 3phase. There's an electric gate which I'm pretty sure is run off the same meter. The docs for the gate operator say that it can run on 120 or 240v single phase.

My question is how do they normally get single 120/240 single phase from 480 three phase and does it matter for the three phase equipment?

step down transformer. for a gate operator, the transformer can be very small

 

[wyliesdiesels]

There's a couple electric boxes that aren't the usual homeowner stuff I'd recognize. One has a switch for the pump. The other is large, maybe 2' tall, with a big rotary switch knob and a small round push button labeled "reset". Next time I'm there I'll open it. There's a lot of what I'll charitably call farm wiring on this place so it might not have breakers/fuses in all the right places.

The meter showed something was drawing 0.009 kW. Since the pump wasn't on, that must be the transformer?

that is the pump controller.

 

[mike93lx]

If you have 480v on your property stay the hell out of the boxes unless you really know what you are doing, which is not the case here.

Call a pro, that is not diy power

 

[no704]

Step down transformer. To 220 threepase than just pick one leg.

 

[yyc_ranger_4x4]

I'd double check that pump, it may be a dual voltage and you're actually running it 208V 3phase.....if you don't have separate 480V and 120V panels with a transformer around, then most likely it's 120/208V 3phase....

 

[ericm]

Its on it's own meter and it's own transformer.

 

[dave*99]

Post a couple photos of all your panels and we can tell you what’s there.
Photos of panels, labels breakers and transformers will tell the story.
Otherwise we will make loads of assumptions and……. Well you get the idea

 

[Jim greengo]

Tap two legs of the 480 and use a single phase transformer to step it down to 120/240.

Assuming it is feed from that and you have a 1/2hp drive motor you’d only need a little 1.5kva transformer. So if you see something like that, well there ya have it.

We used to run the old Lincoln tombstone 240v single phase welders off of 277v on jobsites all the time.
The worked/welded really good from what I remember. Hahaha

 

[Bert_]

We used to run the old Lincoln tombstone 240v single phase welders off of 277v on jobsites all the time.
The worked/welded really good from what I remember. Hahaha

Did they last? I would think the transformer would run kind of hot.

Or just considered it consumable?

 

[Jim greengo]

Did they last? I would think the transformer would run kind of hot.

Or just considered it consumable?

Used them for years that way,really easy to weld.