Compact low cost current sensor and current transformer core for circuit breakers having improved dynamic range

A circuit breaker, comprising:

• a housing;
• a pair of separable contacts;
• a current sensor strap in electrical communication with the contacts;
• an operating mechanism for operating the contacts;
• an electronic trip unit in operable communication with the strap and the mechanism;
• and
• a current transformer comprising:
• a mixed material magnetic core having a first layer of material having a relatively high magnetic permeability, and a second layer of material having a relatively low magnetic permeability abutting the first layer of material;
• wherein the core has a profile with an opening therethrough for accepting the strap;
• and
• a signal generator disposed proximate the core to provide an output signal representative of a magnetic flux associated with the strap;
• wherein the mixed material magnetic core exhibits a dynamic range greater than a dynamic range of a similar shaped magnetic core having only one material of the first layer of material and the second layer of material;
• wherein a root-mean-square current sensing accuracy of the mixed material magnetic core is equal to or greater than about 99.7% in response to a current in the current sensor strap being at about one times the current rating of the circuit breaker.