Motor Starters

  1. Basic uses for a Contactor.
    Contactor: AC and DC  NEMA defines a magnetic contactor as a magnetically actuated device for repeatedly establishing or interrupting an electric power circuit. Contactors are used in conjunction with pilot devices to automatically control high current loads.
    Contactors and Pilot Devices 
  2. Explain how arc suppression is applied to contacts.
    1. One of the main reasons contacts wear is the electric arc that occurs when contacts are opened under load.
    2. The sooner the arc is extinguished the better as that if allowed to continue the hot arc will melt the contact surface. Most contactors contain some type of arc chamber to help extinguish the arc.
    3. The type of load (resistive versus inductive).
      Inductive loads last the longest amount of time due to the magnetic fields stored energy.
    4. How quickly the contactor operates. The faster the speed of contact separation the quicker the arc will be extinguished     
  3. Discuss the major factors in selecting the size of a contactor and type of enclosure.
  4. Explain the difference between a contactor and a motor starter.
     Contactor and Motor Starter
  5. Explain the function and operation of motor overload relays.
    The overload relay protects the motor from overheating and burning up. Show how overloads work.
  6. Compare NEMA and IEC types of contactors and starters.
    IEC are smaller and rated differently by load type.
  7. Understand the operation of a solid-state contactor and starter.
    Go Over how SCR ,transistors and Soft Starts works.