CIRCUIT BREAKERS
Electrical Distribution Systems
Figure 7 Simple Circuit Breaker Control Circuit -
Breaker Open
To close the remotely-operated circuit breaker, turn the circuit breaker control switch to the close
position. This provides a complete path through the closing relay (CR) and energizes the closing
relay. The closing relay shuts an auxiliary contact, which energizes the closing coil (CC), which,
in turn, shuts the circuit breaker, as shown in Figure 8. The breaker latches in the closed
position. Once the breaker is shut, the "b" contact associated with the closing relay opens,
de-energizing the closing relay and, thereby, the closing coil. When the breaker closes, the "a"
contact also closes, which enables the trip circuit for manual or automatic trips of the breaker.
The circuit breaker control switch may now be released and will automatically return to the
neutral position.
To open the circuit breaker, turn the circuit breaker control switch to the trip position. This
action energizes the trip coil (TC), which acts directly on the circuit breaker to release the
latching mechanism that holds the circuit breaker closed.
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