Circuit Breakers

A Circuit Breaker is a protective device designed to open the circuit when a current load is in excess of rated breaker capacity. If there is a short of 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. The first is identified simply as a Circuit Breaker in Electrical Diagnosis. This type will open when excessive current passes through it for a period of time. It will close again after a few seconds. If the cause of the HI current is still present, it will open again. It will continue to cycle open and closed until the condition causing the HI current is removed.

The second type of Circuit Breaker is identified in Electrical Diagnosis as a Positive Temperature Coefficient (PTC) Circuit Breaker. This type increases its resistance greatly when excessive current passes through it. The excessive current heats the PTC device. As the device heats, its resistance increases, thus the name, "Positive Temperature Coefficient." Eventually the resistance gets so HI that the circuit is effectively open. Unlike the ordinary Circuit Breaker, the PTC unit will not reset until the circuit is opened, removing voltage from its terminals. Once voltage is removed, the Circuit Breaker will re-close within a second or two.