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Thread: Circuit Components for a control unit

  1. #1
    Associate Engineer
    Join Date
    Mar 2012

    Circuit Components for a control unit


    I am designing a control system to power and control a 3phase motor/pump. the hydraulic part is ok but the electrical part I am trying to figure out what circuit componets I reuqire to make it a safe system. (a professional comapny will bild this for me but i wld like to understand the system myself to control the cost)

    I assume I need the following:
    1. circuit Breaker (RCD)
    2. Contactor
    3. Relay stack

    I wonder how the level switch and pressure switches should be wired in the system. I am trying to look for eqipment in RS and Farnell...

    Any block diagrams / pointers would be fantastic.


  2. #2
    Technical Fellow
    Join Date
    Feb 2011
    I have a single phase 240vac control on my 365' deep well. The off-the-shelf high/low pressure switch costs about 24-bucks, the 50-A contactor I bought surplus for $30. It is 3-ph but I only use one phase contacts and the 240vac activation coil.

    This controls the contactor.

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