Star Configuration 3 Phase Motor

[Sam Fitz-gerald]

Hi Guys

Currently studying my Level 2 and have a question regarding star configuration on a 3 phase motor. Can anybody tell me why are the each end of the coils not opposite each other? Since there is a link in place should it not matter if U1 connected to W2 ect?

Does it have anything to do with incoming phases?

Any feed back would be great!

 

[Silly Sausage]

................

 

[Spoon]

This may help.

 

[Silly Sausage]

That's what I was trying to type out, but I was being distracted by the radio and it turned into a whole load of garbled incoherent garbage!

 

[westward10]

I think I see what you are getting at. You are saying to connect U1, V2 and W2 at the star point with the lines to U2, V1 and W2. By doing this you are effectively changing the supply configuration and it will go the other way, I think.

 

[Spoon]

I thought the OP was questioning why U2 was not opposite U1... and so on.... I could be wrong..

 

[Deleted member 26818]

Hi Guys

Currently studying my Level 2 and have a question regarding star configuration on a 3 phase motor. Can anybody tell me why are the each end of the coils not opposite each other? Since there is a link in place should it not matter if U1 connected to W2 ect?

Does it have anything to do with incoming phases?

Any feed back would be great!

View attachment 46283

I think it’s just to show the current flow.
Live in on one terminal, return out on the next terminal along.

 

[Michael J]

Spoon has got right

 

[telectrix]

as spoon's diagram. it's so you can alter the links for delta.

 

[*-jester-*]

Yes, as Spoon & telectrix say, it's so that you can reconfigure the links in the terminal box to run the motor in 'delta' depending on the supply voltage or speed of the motor.

 

[Lucien Nunes]

Since there is a link in place should it not matter if U1 connected to W2 ect?

As others have posted, the reason the pairs of terminals are not the start (1) and finish (2) of each winding, (U1-U2, V1-V2, W1-W2) is that it simplifies fitting solid links across the studs to connect the motor for delta. Moving the links to the delta position connects the finish of each winding to the start of the next (W2-U1, U2-V1, V2-W1).

It is essential to observe the correct phase of each winding. Connecting W2-U2, U1-V1, V2-W1 for example, puts the windings in delta but with winding U out of phase. This effectively forms a short-circuited transformer that would either rapidly overheat or hopefully immediately trip the protection. The same would result in star with U2-V1-W1 strapped and the supply on U1, V2, W2. The configuration of studs used makes these mistakes almost impossible.