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Why we use motorized circuit breaker?

  1. Mar 28, 2012 #1
    hi all....
    i want to know you buddy..
    why we use motorized circuit breaker along with under voltage trip (utp) and how motorized circuit breaker works along with under voltage trip (utp)....
    i want to know briefly about this procedure....
    your answer will be appreciate.
    thanks advance........
  2. jcsd
  3. Mar 30, 2012 #2
    Circuit Breakers need a way to operate. This can be locally (when you stand in front of the CB) or remotelly by giving an electrical signal commanding the circuit breaker to close.
    Before to be able to close CB you have to charge a strong spring inside CB. This charged spring is used to close CB contacts internally.

    So for local operation you manually charge the spring using a particular lever for that purpose. With a button mounted on the CB front face, you press it and you close the CB.

    When you want remote operation of the CB you need a kind of motor to charge the internal spring (so we call this CB motorized).
    Moreover, for remote operation you need a couple of electrical reles (coils) such as "close coil" and "open coil". This coils are capable to be remotelly energized by a signal and thus can close / open the CB.

    Since we talk about open/close coils it is clear that coils need auxiliary power to operate. If for some reason auxiliary power is lost, then you are not able to operate the coils (close / open). Imagine that you have sucesfully closed circuit breaker (by remotely energizing close coil) but during operation for some stupid reason auxiliary voltage is lost . As a result you can't open the CB!
    UnderVoltage Coil comes to cover this hole.
    In case auxiliary power required for the coils to work is lost, the undervoltage trip coil forces the opening of the circuit breaker.
    Notice that undervoltage trip coil is optional. Close and Open coils is mandatory for remote operation.
  4. Apr 2, 2012 #3
    thanks ge.vasiliou....this is go0d knowledge for me.............
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