Patent ID: 8830026

Claim:
A thermal trip unit for a circuit breaker, the circuit breaker including a primary conductive path having a first impedance for conducting a load current, the thermal trip unit comprising: a shape memory alloy (SMA) member having a coil shape defining an inside diameter, and having a second impedance, the SMA member adapted to change from a first shape to a second shape at a predetermined thermal condition; a holding member comprising a cavity configured to receive said SMA member therein, the holding member being coupled electrically in series with the circuit breaker primary conductive path, said holding member arranged to operatively support said SMA member; a conductive tube, said tube being electrically connected to said holding member and disposed within said holding member cavity and further disposed at least partially within the inside diameter of said SMA member; wherein said SMA member is at least partially disposed within said cavity and arranged to trigger a trip response of the circuit breaker at said predetermined thermal condition; wherein said primary conductive path is operatively arranged and disposed to substantially limit a current flow through the SMA member and wherein the first impedance is less than the second impedance.