Single phase supply

[Justin91]

If I have a 240/480 volt dual voltage single phase motor connected by 2.5mm 2c+e to an isolator and then just 1mm flex coming out with active, neutral and earth connected is it possible the power supply to be 480v or is it most definitely 240v

 

[Lucien Nunes]

There would be three wires in either case. If it is 240V, they will be active, neutral and earth. On a standard split-phase 480V system there would be two actives and earth, with no connection to the neutral. You can usually identify which voltage the motor is set up for, by comparing the positions of wires and links in the terminal box with the diagram that is usually inside the lid. If in any doubt, post pics of the above plus the data plate.

 

[Justin91]

There would be three wires in either case. If it is 240V, they will be active, neutral and earth. On a standard split-phase 480V system there would be two actives and earth, with no connection to the neutral. You can usually identify which voltage the motor is set up for, by comparing the positions of wires and links in the terminal box with the diagram that is usually inside the lid. If in any doubt, post pics of the above plus the data plate.


here are some photos

 

[Megawatt]

There would be three wires in either case. If it is 240V, they will be active, neutral and earth. On a standard split-phase 480V system there would be two actives and earth, with no connection to the neutral. You can usually identify which voltage the motor is set up for, by comparing the positions of wires and links in the terminal box with the diagram that is usually inside the lid. If in any doubt, post pics of the above plus the data plate.


here are some photos
View attachment 58668View attachment 58669View attachment 58672

Justin that is a dual voltage motor but I cant understand the configuration of the brass factory jumpers which could possibly go phase to phase as stated above the name plate should have all the info you need to know. It should read 3 phase or single phase motor. I’ve never seen a 480vac motor that wasn’t 3phase and the flex is no factor at all

 

[Justin91]

My only concern is I isolated and disconnected in a hurry and had to order a new motor and order a single phase 240v motor assuming the supply was 240v, now my boss is saying it’s configured for 480v supply and asking if I’m sure the supply was 240v.

 

[Megawatt]

My only concern is I isolated and disconnected in a hurry and had to order a new motor and order a single phase 240v motor assuming the supply was 240v, now my boss is saying it’s configured for 480v supply and asking if I’m sure the supply was 240v.

I read your profile and being a trainee your boss should have to tell you what it was before hand. My friend if you are not 100% positive of the voltage and 3 phase or single or single phase. I’m worried about you wiring that motor not knowing more than you know. Call the manufacturer where you bought that motor for more information. If your boss is so sure about the voltage and wiring let him wire it up. Under no circumstances should you wire that motor. With the factory jumpers is for wiring it in a star or delta configuration Good luck

 

[Justin91]

100% with you on that unfortunately my boss makes me do heaps of stuff I know I shouldn’t be doing I pretty much rely on advice and out of work training.

 

[Megawatt]

100% with you on that unfortunately my boss makes me do heaps of stuff I know I shouldn’t be doing I pretty much rely on advice and out of work training.

We would like to advise you but we have no way of knowing the voltage or single or 3 phase and I cannot steer you in the right direction. Tell you boss I said that it is to dangerous for you to wire. Let this be a lesson and don’t get in a hurry to disconnect it and take pictures and draw how it’s wired before you unhook it. If we had pictures I still wouldn’t want to tell you stop by step. Please stay safe, a motor is not worth your life

 

[ElectroChem]

Justin we need a photo of the underside of the terminal cover lid, that's where the wiring diagram is often found.

If you've ordered a fixed 240V motor and it's a 480V supply then you're out of luck, though there should be 240V around in the shed to run a new supply if needed.

Megawatt, it's definitely a single phase motor. 240/480 split phase is common in rural Australia and the big capacitor is a give-away. Our industrial 3-phase is generally 415V.

 

[Justin91]

Even is it is 480v supply so be it, I’m more curious to learn how you get 480V in single phase active, neutral and earth, a step up transformer maybe? Note the building does have 3 phase but 3 phase cable is not running to the motor.

 

[ElectroChem]

Even is it is 480v supply so be it, I’m more curious to learn how you get 480V in single phase active, neutral and earth, a step up transformer maybe? Note the building does have 3 phase but 3 phase cable is not running to the motor.

Now you've got me interested, it would be very unusual to have 3-phase and 480V split in the same place.
The 480V split phase is obtained from a step-DOWN transformer, from a 12 or 19kV SWER overhead supply line. This is only used in remote areas, if you've got 3P+N coming from town supply, you don't need SWER.
Makes me think your boss is talking out his arse insisting the old motor was 480V.

 

[Justin91]

I’m with you and I’m pretty certain it’s just 240v supplies the motor and my boss is making me doubt myself and I’m hoping I am right and I get to prove him wrong. And yes it’s a town supply in a well built up area in a small shopping centre. But thank you for telling me how 480v is achieved for future knowledge.

 

[Lucien Nunes]

I am concerned that it does look like it's wired for 480V. If you can get a pic of the underside of the terminal cover it may well have the wiring diagram, but I guess what you posted is all the info you have.

There seem to be six leadouts from the windings, indicating that there are two sections of main winding but only one capacitor winding which would be wound for 240V. For 480V operation the capacitor winding is connected across half the main winding, which serves as an autotransformer. An old UK convention was main winding = red/black, aux / cap / start winding = yellow/blue. If the second section of your main winding is brown/white, it all makes sense.

I've sketched how I think it is wired. Assuming the links are set for 480V in your motor, I've shown those as dashed lines. The red/black section and brown/white sections of the main winding are connected in series, with the blue/yellow capacitor winding in parallel with the red/black section only. The 240V link positions would be as shown by dotted lines, with all three windings in parallel. Even if the winding leadout colours don't follow that convention, for 240V I would expect to see either active or neutral connected to three windings, which you do not have. Therefore I think it's set for 480V.

I’ve never seen a 480vac motor that wasn’t 3phase

That's because you're in the US. In the UK and Australia (where this motor is) 3-phase is 400-415V or more recently 690V for large plant. We normally only use 460-480V split phase in rural locations where heavier loads are in use (e.g. farms) but no 3-phase HV is available. If this looks like a 3-phase motor, you need new spectacles!
[automerge]1591519624[/automerge]

 

[Justin91]

thank you for all this information and your sketch it is very useful to me and I am returning to the site in a few days to investigate. I am under the impression yes it is wired for 480v but 240v has been connected and run on this motor for its life time, if this is the case what would the down side be of the motor efficiency?

 

[Lucien Nunes]

The stall torque would be drastically reduced and the speed also low. With some types of load it wouldn't even be able to start, so unless the load is very light I am skeptical about whether it could have been used for a long time on 240V while wired for 480V. Of course, this might be the reason you have been called in to replace it. What does it drive?

Remember that my sketch is only based on what I see in your picture and general knowledge. I give no guarantee that it is correct.