Star delta starting

[dan.h]

Hey all, this is my 1st post so hello to everyone. I was wondering, i know the idea behind a star delta starter etc and would have no worries changing a motor over if i disconnected the old one first. What has got me a little bit confused is if you were to fit a motor and all that was there was the 6 cables to go on to the motor terminals. Its not specific to any job im just curious. Ive searched all over net and cant find anything. Are there any test/stheroy that can be applied so that i could wire the motor up so that when it changes over to delta it isnt all of a sudden gonna try and turn the opposite way.
sorry if its a daft question.
Thanks

 

[raylewis]

Try this schematic on star/delta
Hope it helps


Ray

 

[dan.h]

yeah that is helpful thanks, i was told as a rule of thumb to wire it up in that fashion shown there. could any body explain to me why it is like that. I havent had a great deal of experience with star/delta mostly dol's and the occasional inverter.

 

[raylewis]

Starting up in star connection draws less start up current but not to healthy to run on due to lower torque
therefore change over to delta for running.

Hope this helps

Ray

 

[dan.h]

Cheers mate, yeah i know why we use them and how they work just abit unsure how to work out where the cables would go onto the motor if all i had were six cables and no record of how they come off the orignal motor. I didn't know if there was a way to test before connecting or do most people just connect them like as in the diagram you posted up. Thanks again

 

[raylewis]

If no labelling on motor terminals
Pick any one terminal and mark it as U1 test on ohms and find U2 - low ohmic value
Others will be infinity
Mark that one as U2

Pick other teminal and mark as V1
Continue as above and mark as V2
Remaining two must be W1 & W2(test to check)mark as W1 and W2
Note : Ohmic value of three must be the same for balance

Connect to contactors as per schematic and check rotation
If rotation incorrect change two of the incoming supply phases L1,L2 or L3
Will attatch other schematic for you to look at, I think this will help.

Ray

 

[raylewis]

Hope this attatchment helps

Ray

 

[dan.h]

Hey raylewis, thanks very much for your help just studied that schematic you provided and it all clicked into place lol. Yeah so going on what you said just bell out to find each of the windings. I think id double check the coulours with regards to how there wired up in the contactors, and then just connect up as per schematic diagram.