WHAT MAKES A MAGNETIC CIRCUIT BREAKER TRIP?
The hydraulic/magnetic circuit breaker “Series Trip” configuration consists of current sensing coil connected in series with a set of contacts. (Figure 1) Figure 1 Inside the coil is a non-magnetic delay tube housing a spring-biased, moving magnetic core. An armature links the contacts to the coil mechanism, which functions as an electromagnet. When the contacts are open, there is no current flow through the circuit breaker, and the coil develops no electromagnetic energy. When the contacts are closed, current flow begins. (Figure 2) Figure 2 – Rated Current or Less As the normal operating or “rated” current flows through the sensing coil, a magnetic field is created around that coil. When the current flow increases, the strength of the magnetic field increases, drawing the spring-biased, movable magnetic core toward the pole piece. As the core moves inward, the efficiency of the magnetic circuit is increased, creating an even greater electromagnetic force. When the core is fully “in”,
