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Discussion Starter · #1 ·
I have a 11 KW pump. the wiring is in a star-delta pattern. obviously, i have to use 3 contactors. what is the value of the current in each contactor first of all, in the start and then in the running of the pump?
 

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I can name that tune in two contactors.

Any reason why you wouldn't use a pre-made star-delta starter with the timers and all, or just put the darned thing on a VFD to begin with and be done with the archaic start arrangement?
 

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nicolaschalhoub said:
I have a 11 KW pump. the wiring is in a star-delta pattern. obviously, i have to use 3 contactors. what is the value of the current in each contactor first of all, in the start and then in the running of the pump?
Shame on you. As an ENGINEER, you should know better than to ask a question without giving enough information to be able to formulate an answer.
 

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Discussion Starter · #4 ·
-.-

I am an electronic engineer, not an electrical engineer.
i'm specialized in programming, and handling PCBs.
nevertheless, i was just asking to learn more on how to work with pumps.
 

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nicolaschalhoub said:
I am an electronic engineer, not an electrical engineer. i'm specialized in programming, and handling PCBs. nevertheless, i was just asking to learn more on how to work with pumps.
So does that mean you don't work with formulas? You gave 1 value, 11 KW, and want to calculate current. This is something that you do in electronics as well, don't you? What is the voltage for a start?
 

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I am an electronic engineer, not an electrical engineer.
i'm specialized in programming, and handling PCBs.
nevertheless, i was just asking to learn more on how to work with pumps.
Look at the motor name plate for Star (WYE) Current and Delta Current

Star is the first current and the Delta is the second



Good luck
 

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I have a 11 KW pump. the wiring is in a star-delta pattern. obviously, i have to use 3 contactors. what is the value of the current in each contactor first of all, in the start and then in the running of the pump?
I think I would struggle trying to figure out where to fit a third contractor into the start sequence.
How old is this motor, is it in service now or has it been, has it been tested/ meggered, what voltage is your system?
 

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You will have 3 contactors. 2 of them (Start and Run) can be sized for 58% of the current, the other (Star) at 33%. But as others have said, don't over think this. Sometimes there are other issues such as mechanical interlocks that are necessary do not work on mis-matched contactors so you end up with all 3 being the same size, it totally depends on the contactor mechanical designs. Just buy a pre-made star-delta motor starter, the manufacturer takes care of all of that for you.
 
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