Circuit Protection - Circuit Breakers
A circuit breaker is a protective device that is designed to
open the circuit when a current load is in excess of the rated
breaker capacity. If there is a short or other type of overload
condition in the circuit, the excessive current will open the
circuit between the circuit breaker terminals. Two types of circuit
breakers are used.
Circuit Breaker: This type opens when
excessive current passes through it for a period of time. It closes
again after a few seconds, and if the cause of the high current is
still present, it will open again. The circuit breaker will
continue to cycle open and closed until the condition causing the
high current is removed. |
Positive Temperature Coefficient (PTC) Circuit
Breaker: This type greatly increases its resistance when
excessive current passes through it. The excessive current heats
the PTC device, as the device heats its resistance increases.
Eventually the resistance gets so high that the circuit is
effectively open. Unlike the ordinary circuit breaker the PTC unit
will not reset until the circuit is opened, by removing the voltage
from its terminals. Once the voltage is removed the circuit breaker
will re-close within a second or 2. |
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