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6.2: Control Relays

  • Page ID
    3667
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    A YouTube element has been excluded from this version of the text. You can view it online here: https://openoregon.pressbooks.pub/hydraulics/?p=174

    Describe a control relay and identify its purpose in an electrically controlled system

    Describe the similarities and differences between a contactor and a control relay

     

    Describe the keyed base associated with an ice cube relay and identify advantages of using keyed bases.

     

    Draw the NEMA schematic symbol for a control relay with a coil, two NO SPST contacts, and two NC SPST contacts

     

    Draw the NEMA schematic symbol for a control relay with a coil and two SPDT C form/transfer contacts

     

    Draw the IEC schematic symbol for a control relay with a coil and two SPDT C form/transfer contacts

     

    Number the terminals of the above control relays

     

    Describe a solenoid and discuss its function and purpose inside a control relay

     

    Describe the components of a control relay and identify their purpose

     

    Define and differentiate between rated voltage, pickup voltage, hold in voltage, and dropout voltage

     

    Describe why a 120V AC coil cannot be used with 24V DC

     

    Differentiate between inrush and sealed in current

     

    Describe why a means of voltage spike suppression must be used for certain coils

     

    Discuss points of inspection and maintenance procedures for control relays

     

    Describe the purpose of bifurcated or split contacts in a control relay

     

    Differentiate between make, break, and continuous current carrying capacity

     

    Describe a solid state relay in general terms

     

    Discuss the PLC and its relation to the control relay (comment at 25:40)

     

    BONUS: Describe the behavior of this ladder logic diagram making use of a control relay and its associated contacts for the following sequence of actions:

    both STOP and START in their deactivated state

    operator presses and releases START

    operator presses and releases STOP

    ladder.png