Magnetic Trip Element

A magnetic trip element circuit breaker uses an electromagnet in series with the circuit load as in figure 20. With normal current, the electromagnet will not have enough attraction to the trip bar to move it, and the contacts will remain closed as shown in figure 20, view A. The strength of the magnetic field of the electromagnet increases as current through the coil increases. As soon as the current in the circuit becomes large enough, the trip bar is pulled toward the magnetic element (electromagnet), the contacts are opened, and the current stops, as shown in figure 20, view B.