Running 3ph motors on single phase

[flyingsparks]

Hi. I have a large fan which I am pretty sure is a 3phase motor, but has been supplied with the links in on the terminals for it to run on single phase. This is how its supplied:

Can someone confirm this is correct linking? Sorry cant remember which is U1 V1 W1 etc..

Oh and where would you connect live and neutaul?? The speed controler which supplys the fan has an aux output too if that means anything?

Also, what is the procedure for reversing it if it is turning the wrong way round, I know that if it was 3 phase you just change 2 phases, but on single phase?

Thanks.

 

[Spark123]

Vent Axia? I think they are capacitor start motors, don't think they are 3 phase unless you have specifically bought a 3 phase one. I don't think you can run a 3 phase motor on single phase unless you have an inverter or the likes. What does it say on the label? You can always try the vent axia website clicky, select the fan and then the wiring diagram pdf file from the RHS column.

 

[flyingsparks]

Thanks for your reply.. its not vent axia, cant remember the make now. I will find it out and then look up a wiring diagram.

Any ideas how you would reverse a single phase motor?
Thanks.

 

[Spark123]

It generally depends on the motor, really need more info. It might just be a case of swopping over the polarity of the start winding.

 

[Lectrician]

The position of the links suggests it is single phase. Three phase motors usually have the brass links all parallel with each other. You cannot convert a three phase motor to single phase without re-winding.

What are the connections marked as? What are the internal motor cables marked as?

 

[flyingsparks]

The motor isnt here so I cant tell you the connection labels unfortunatly. With it connected in what was thought was the correct way, the motor wasa turning but all be it not very fast (even with the speed control turned up and with the trimming pot turned up too. The fan is a new replacement for one which after only a few hours use melted the plastic terminal box. The spark who did it was bloody useless, I got asked to have a look because the owner didnt think the spark knew what he was doing (and he didnt - SWA not terminated with gland, lots of copper showing etc.) I think it cant have been wired correctly and it got hot.

Or possibly the wrong speed controller was used, its electronic, and possibly that fan needs a transformer type of speed controller.. what do you think?

Thanks.

 

[breezer]

need more info on the fan really.

where is it for? (being as it sounds like its so big)

when you go back can you take a camera and upload the pics?

 

[flyingsparks]

Its for extract in a pub kitchen canopy. Its a big thing - about 600mm diameter. Yea I can do, I'm currently trying to get hold of the make and model to look up a wiring diagram.
Thanks

 

[Lectrician]

ELTA fans? They are a typical extractor fan supplier for canopies.

Usually single phase unless the canopy is huge.

Threephase fans for canopies are speed controled via transformer tapps selected via a rotary 'click' switch. Single phase by a standard type controller.

You should match the controller to the fan.

You should also utilise the thermistors in the fan in conjunction with a DOL starter to provide over heat protection, or the manufacturer warrenty is ususally void.

These extract systems are usually complimented by an intake fan to balance the pressures, and these are interlocked to the main gas valve to prevent the gas being used unless both fans are running at the required speed. There is also usually EM stops to kill the fans and gas valve in an emergency, and this is also often interfaced to a firealarm in some premises - fire alarm kills fans and gas.

 

[flyingsparks]

Thats it, ELTA. Looking at a catalogue, the specific fan we have has a dash next to the 'electronic controller' coloumn, suggesting perhaps it needs one of the transformer controllers?

There is an intake fan the same, but that hasnt been installed yet. And yep it is all coupled into a gas interlock.

Any reason why it wouldn't be OK to put in a DP switch for now to get them out of trouble to have the fan on flat out?

Where would the connections be made onto the fan itself then, as obviously only live and neutraul, and there is 3 options for connecting.. or could one be a start up winding, which is controlled from electronics in the speed controller? Thanks.

 

[plugwash]

The position of the links suggests it is single phase. Three phase motors usually have the brass links all parallel with each other. You cannot convert a three phase motor to single phase without re-winding.

Sure you can, you paralell two of the windings so they act as a single large winding providing the bulk of the power. Connect the remaining wiring in series with a capacitor to introduce some rotation to the magnetic field.

It won't run as efficiantly or as powerfull as on three phase but it should run.

 

[Lectrician]

The ELTA fans and controllers for single phase typically need three cores plus earth to the fan. To run the fan without a controller, you need to alter the copper links in the fan terminal housing to suit. You woul dneed to change it back for use with a controller.

Maybe there is a tech sheet on the website with the diagrams?

 

[Lectrician]

The position of the links suggests it is single phase. Three phase motors usually have the brass links all parallel with each other. You cannot convert a three phase motor to single phase without re-winding.

Sure you can, you paralell two of the windings so they act as a single large winding providing the bulk of the power. Connect the remaining wiring in series with a capacitor to introduce some rotation to the magnetic field.

It won't run as efficiantly or as powerfull as on three phase but it should run.

Technically yes - But do manufacturers actually ever document this!?! You should always fit to the spec given. Doing it that way you may also overheat the windings and motor.

 

[breezer]

bearing in mind this is in a pub. not really a good idea

 

[flyingsparks]

The ELTA fans and controllers for single phase typically need three cores plus earth to the fan. To run the fan without a controller, you need to alter the copper links in the fan terminal housing to suit. You woul dneed to change it back for use with a controller.

Maybe there is a tech sheet on the website with the diagrams?

What is the third core for? How would you alter the links to get it to run without the controller?

The ELTA website is under construction by the looks of it and have nothing there!