| Air Circuit Breaker
| A circuit breaker that makes and breaks power circuits in air using arc chutes. |
| Arcing
| The effect generated when electrical current bridges the air gap between two conductors that are not touching. |
| Arc Chute
| A component of the arc extinguisher in a low voltage circuit breaker. It elongates and cools an arc. |
| Arc Extinguisher
| A common method used to extinguish an arc. In general, it confines, divides and cools the arc. |
| ANSI
| American National Standards Institute. |
| Butt
| A design type for making contacts in a circuit breaker. |
| Circuit Breaker
| A reusable overcurrent protection device. After tripping to break the circuit, it can be reset to protect the circuit again. |
| Connected Position
| The position in which the circuit breaker is fully connected and functional. |
| Contacts
| Method to open and close the circuit as the contacts come together or separate. |
| Continuous Current Rating
| The amount of current the breaker can carry continuously at 60 cycles without exceeding the temperature rise limit, according to ANSI charts. |
| Control Voltage
| Voltage used to operate secondary devices. |
| Coordination
| The process of selecting and applying circuit breakers in an electrical distribution system to localize a fault condition and restrict power outages to the equipment affected |
| CSA
| Canadian Standards Association |
| Disconnect Position
| The position in which neither the primary nor secondary electrical connections of the circuit breaker are made. This position is often used as a storage position for the circuit breaker within its enclosure. |
| Drawout
| A type of circuit breaker that can be moved into or out of its structure without unbolting, often on a racking mechanism. |
| Faceplate Shield
| A device to protect the operator from dangerous voltages while the breaker door is open. |
| Finger
| A design type for making contacts in a circuit breaker. |
| Finger Clusters
| Automatic main disconnect devices for a circuit breaker. |
| Fixed
| A type of circuit breaker that is bolted into a fixed position with bus or cable mechanically bolted to breaker terminations. |
| Ground Fault Protection
| A form of protection which reacts to ground fault conditions. |
| IEEE
| Institute of Electrical and Electronic Engineers. An objective technical organization made up of manufacturers, users, and other general interest parties |
| Integrally Mounted Trip Unit
| The trip unit is inside of, or part of, the circuit breaker. |
| International Electrotechnical Commission
| Abbreviated IEC. This organization is associated with equipment used internationally. |
| Interrupting Rating
| Also “Ampere Interrupting Capacity (AIC).” A rating of the amount of current that a protective device, such as a fuse or circuit breaker, can safely interrupt. |
| Instantaneous Protection
| A form of protection which reacts to high level fault conditions. |
| Lever
| The act of moving the breaker from one position to another. |
| Long Delay Protection
| A form of protection which reacts to overload conditions and certain short circuit conditions. |
| NEMA
| National Electrical Manufacturers Association. |
| SF
6 | An arc extinguishing technology involving the use of sulfur hexafluoride gas. |
| Short Delay Protection
| A form of protection which reacts to short circuit conditions. |
| Short Time Rating
| A rating for how fast a circuit breaker will open, expressed in cycles. |
| Stored Energy
| A mechanism used to overcome inherent forces opposed to the breaker closing process, which stores energy until it is needed to help open the breaker. |
| Test Position
| The position in which the circuit breaker’s primary connections are disconnected. Secondary connections are not disconnected and testing can be safely performed because the circuit breaker is not energized. |
| 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 case of a short circuit or overload condition. |
| Underwriter’s Laboratories
| UL. An independent laboratory that tests equipment to determine whether it meets certain safety standards when properly used. |
| Vacuum
| An arc extinguishing technology. Features a pair of separable contacts enclosed in a vacuum-tight envelope. Because the environment inside the interrupter envelope is a vacuum, an arc cannot be sustained easily. |
| Withdrawn Position
| In this position, the circuit breaker has no electrical connections. It is far enough out of its enclosure to permit inspection and maintenance. |
| Withstand Rating
| See “Short Time Rating.” |
