| Ampere Rating
| A rating of the amount of current a protective device will carry continuously without deteriorating or exceeding temperature rise limits. |
| ANSI
| American National Standards Institute. |
| Arc
| The effect generated when electrical current bridges the air gap between two conductors that are not touching. |
| Arc Extinguisher
| A common method used to extinguish an arc. In general, it confines, divides and cools the arc. |
| Circuit Breaker
| A reusable overcurrent protection device. After tripping to break the circuit, it can be reset to protect the circuit again. |
| Contacts
| Method to open and close the circuit as the contacts come together or separate. |
| CSA
| Canadian Standards Association. |
| Current Zero
| A point in the AC current sine wave where the value is zero. Also “Zero Point”. |
| Deionizing
| The process of removing conduction ions, thus permitting arc extinction. |
| Dielectric
| Any insulating material between two conductors. |
| Dielectric Strength
| The maximum voltage a dielectric can withstand without breaking down. |
| Drawout Mounted
| A type of circuit breaker that 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
| A type of circuit breaker that is bolted into a fixed position with bus or cable mechanically bolted to breaker terminations. |
| Harmonics
| Multiples of fundamental frequency that when added together result in a distorted sine wave causing noise. Usually created by electronic equipment. |
| IEC
| Abbreviation for International Electro-technical Commission. This organization is associated with equipment used internationally. |
| IEEE
| Institute of Electrical and Electronic Engineers. |
| 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. |
| Loadcenter
| A device that delivers electricity from a supply source to loads in light commercial or residential applications. |
| 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 carries mandatory compliance. |
| NEMA
| National Electrical Manufacturers Association — establishes manufacturing standards to meet the requirements of UL. |
| Overload (or Overcurrent)
| A condition in which current is in excess of the normal load being drawn. |
| Over-Toggle
| Handle is operated to the point of no return and the spring-assisted mechanism operates the breaker. |
| Panelboard
| A wall-mounted electrical power distribution device for use in commercial and industrial applications. It provides circuit control and overcurrent protection for light, heat or power circuits. |
| Quick-Make, Quick-Break
| Speed with which contacts open or close, regardless of the speed of handle operation. |
| RMS
| Root Mean Square. RMS Current is also referred to as “effective current.” It is the square root of the average of all the instantaneous currents (current at any point on a sine wave) squared. |
| Short Circuit
| An electrical fault created when two exposed conductors touch or a fault in an electrical system caused by abnormally high current flow due to insulation failure. |
| Shunt Trip
| A device used to trip a circuit breaker remotely. |
| Switchboard
| Equipment in which a large block of electric power is delivered from a substation and distributed throughout a building. |
| Thermal Magnetic
| The predominant trip unit technology used in the domestic market. A bimetal and an electromagnet work together to provide overload and short circuit protection. |
| Three-Phase
| Three streams of electricity rotated through a magnetic field and distributed on three cables. |
| Trip Unit
| Device that trips the operating mechanism in case of a short circuit or overload condition. |
| Two-Step Stored Energy
| Separate opening and closing springs operate the contact mechanism allowing for rapid reclosing and safety. |
| UL
| Underwriters Laboratory. An independent laboratory that tests equipment to determine whether it meets certain safety standards when properly used. |
| Vacuum Interruption
| This common extinguishing method encloses contacts in a vacuum where an arc cannot be easily maintained. |
| Zero Point
| Also “Current Zero.” A point in the AC current sine wave where the value is zero. |
