| Ambient Compensated
| An electromechanical circuit breaker whose trip element is calibrated/adjusted to perform as required in a specific surrounding temperature condition. |
| ANSI
| Abbreviation for American National Standards Institute. It does not develop standards, but functions as a coordinating body for the purpose of encouraging development and adoption of worthwhile standards. |
| Arcing
| The discharge of electric current across a gap between two points. It occurs between breaker contacts each time a breaker interrupts a current. |
| Bus
| The conductor(s), usually made of copper or aluminum, which carries the current and serves as a common connection for two or more circuits. |
| Clearing Time (Circuit Breaker)
| The total elapsed time between the time the specified overcurrent causes a release device to be actuated and the instant of final arc extinction on all poles of the primary arcing contacts. |
| Clearing Time (Fuse)
| The total elapsed time between the beginning of the specified overcurrent and the final interruption of the circuit. It is the sum of the melting time and the arcing time. |
| Deionization
| The process of removing conduction ions, thus permitting arc extinction. |
| Drawout Mount
| Breaker can be moved into or out of its structure without unbolting, often on a Racking mechanism. |
| Fault Current
| The surge of amperage created during an electrical failing. |
| Fixed Mounted
| The breaker is bolted into a fixed position with bus or cable mechanically bolted to breaker terminations. |
| Fixed Trip
| The trip unit of the circuit breaker is set for a specific trip rating and cannot be adjusted if a new trip rating is needed. The circuit breaker must be replaced. |
| IEC
| International Electro-technical Commission. |
| Interchangeable Trip Unit
| If a new trip rating is required for an application, only the trip unit needs to be replaced, up to the maximum current rating of the breaker frame. |
| Interrupt Rating
| The maximum short circuit current that an overcurrent protective device can safely interrupt. |
| IP
| Ingress Protection: protection from the entry of dust, liquid, or other material into the enclosure and/or protection of human contact with live electrical parts. |
| Knockouts
| Pre-stamped holes for the insertion of conduit or conductors into an enclosure. |
| Low Level Fault
| Can range in magnitude from just above full load current to 10 or more times normal current. Does not usually cause noticeable damage immediately, but can lead to eventual problems. |
| Molded Case Circuit Breaker
| A circuit breakers designed to provide circuit protection for low voltage distribution systems. Used primarily in panelboards and switchboards. |
| NEC
| National Electric Code — a set of electrical installation standards applicable throughout the U.S. and published by the National Fire Protection Association. The NEC works with UL requirements and usually carry mandatory compliance. |
| NEMA
| Abbreviation for National Electrical Manufacturers Association. An organization of manufacturers of electrical products. |
| Nuisance Tripping
| An unintentional trip at below set pickup currents, usually the result of circuit conditions or equipment applications. |
| Quick-Make, Quick-Break
| Speed with which contacts open or close, regardless of the speed of handle operation. |
| Rating Plug
| Used to change the continuous current rating of an electronic trip unit. |
| Shunt Trip
| A device used to trip a circuit breaker remotely. |
| Thermistor
| A temperature-sensitive resistor that changes its electrical resistance with a change in temperature. |
| Trip-Free
| Breaker cannot be prevented from tripping, even when holding the handle in the ON position. |
| Trip Unit
| Device that trips the operating mechanism in the event of a short circuit or overload condition. |
