3mm Gap

An IEC (European) safety agency standard that requires a minimum 3 millimeter gap to exist between contacts when in the OFF position. Any gap of 3mm or greater is considered a full gap. Full gap is a requirement when the switch is used as the main power disconnect for a product.A

Actuation Force

See Operating Force.

Actuator

An actuator is the mechanical component used to manually turn a switch or circuit breaker on and off.

Alternate Action (double action)

A "Push-On/Push Off" switch action, typically referring to maintained circuit pushbutton switches.

Alternating Current (AC)

Term applied to an electric current or voltage that reverses its direction of flow at regular intervals and has alternately positive and negative values, the average value of which over a period of time is zero. Compare Direct Current.

Ambient Temperature

The temperature of the surrounding cooling medium in which the heat of the device is dissipated.

Ampacity

The current-carrying capacity of a conductor or device.

Ampere (A)

The unit of measurement of electric current. It is proportional to the quantity of flow of electrons through a conductor past a given point in one second. It is the unit current produced in a circuit by one Volt applied across a resistance of one Ohm.

Arcing

Sparking that occurs each time a switch is turned on or off, except in very low voltage and low current applications. This sparking can burn up the switch contacts and reduce the life of a switch. In general, the arc produced by a DC voltage will be greater and last longer than an AC voltage because DC current has a constant value in relation to ground and zero. AC current has a value that is always rising or falling in relation to zero. Whenever it reaches zero (120 times a second) in cannot produce an arc.B

Branch Circuit

A portion of the wiring system extending beyond the final overcurrent protective device.

Break-Before-Make

Switches that will only complete one circuit at a time, leaving an interval of time between the time one circuit opens and the next circuit closes.

Busbar

An electrical conductor in the form of rigid bars serving as a common connection for two or more electrical circuits.

Butt Action Contacts

Contacts that press "head-on" against each other when closing a circuit.C

Cascade Circuit

A series arrangement of more than one protector connected between the power source and the load.

Center-Off

A switch with three actuator positions. Contact is made (with one or several circuits) in the two extreme positions; in the center position of the actuator, all circuits are off.

Circuit (Electrical)

The closed loop through which electricity can flow.

Circuit Breaker

A device used to open and close a circuit non-automatically, as well as open a circuit automatically when subjected to a predetermined overload current without damaging itself.

Closed Circuit

An electrical circuit that allows an uninterrupted flow of electricity from the source of power, through the conductor or wire, to the load, and then back again to the ground of source of power.

Common Terminal

Line terminal that can be alternately connected to two or more load terminals.

Common Trip

A feature on a multi-pole circuit protector in which an overload on any pole will cause all poles to open.

Conductor

A material or object that permits an electric current to flow easily

Contacts

Components that form the junction of two electrical conductors through which current passes, used for making (closing) and breaking (opening) electrical circuits.

Contact Bounce

The tendency for butt action contacts to bounce apart as they come together. The bouncing action can prolong and arc, or open and close the circuit very quickly several times before coming to a closed position.

Contact Rating

The capacity of contacts to carry an electrical load.

Contact Resistance

The resistance of a pair of contacts, measured at the terminals, which effectively appears in series with the load (mili-ohm range).

Coordination

The ability of a circuit protector with the lowest rating in a cascade arrangement to trip before those with higher ratings (see Cascade Circuit).

Current (Electric)

A flow of electrons in an electrical conductor. The strength or rate of movement of the electricity is measured in amperes. A generic term usually modified by an adjective (i.e., AC or DC), the amount of electrical charge flowing through a conductor, as compared to Volts, which is the force that drives the electrical charge.

Current Limitation

A protective device that reduces the available short circuit peak current to a lesser value.

Current Rating

The maximum current in amperes, at rated current and frequency, that a device will carry continuously under defined conditions without exceeding specified performance limits.D

Dependent Lamp

A lamp or lamps powered by the same circuit that a switch is controlling; the lamp turns on when the switch is activated.

Detent

A feature usually found in slide and rotary switches that denotes where the switch "clicks" into the various positions.

Dielectric Strength

The highest voltage an insulator can withstand without allowing current to flow. Also referred to as breakdown voltage. For switches, also represents the strength between live parts and operator at accessible surfaces.

Direct Current (DC)

Term applied to an electric current or voltage which may have pulsating characteristics, but which does not reverse direction.

Double Break/Double Make

Contacts that open at two separate places on a circuit.

Double Insulation

Denotes an insulation system comprised of functional insulation and protective insulation, with the two insulations physically separated and arranged in such a way that they are not simultaneously subjected to the same deteriorating influences, temperature, contaminants, etc. to the same degree.

Double Pole -DP (switches)

A switch device that opens, closes, or changes connection of two conductors in an electrical circuit.

Double Throw (DT)

A switch that opens, closes, or completes a circuit at both extreme positions of its actuator.

Dry Circuit

A low current circuit that does not generate enough power to generate an arc.

Dump Circuit

A means to remotely trip a circuit breaker without there having to be a current overload.

Duty Continuous

The requirement that demands operation at a constant load for an indefinite period of time.

Duty Cycle

The ratio of on-time and off-time

Duty Intermittent

The requirement that demands operation of alternate intervals of (1) load/no load, (2) load/rest, or (3) load/no load/rest.E

Effective or RMS Value

The value of alternating current that will produce the same amount of energy in a resistance as the corresponding value of direct current.

Equipment Leakage

Commonly referred to as earth leakage or ground fault, an unintentional electrical connection between an energized conductor and "ground". Ground is an arbitrarily decided point whose voltage is taken to zero, in many situations, this point is the actual ground or earth.F

Fault

A defect in the normal circuit configuration commonly referred to as short circuit. Usually due to unintentional grounding.

Fault Current

The current that may flow in any part of a system under fault conditions.

Feeder

All circuit conductors between the service entrance equipment and the final branch circuit protector.

Frequency

The number of cycles through which an alternating current passes per second. Frequency has been generally standardized in the United States electric utility industry at 60 cycles per second (60 hertz)G

Ground Fault

An unintentional electrical connection between an energized conductor and 'ground'. Ground is an arbitrarily decided point whose voltage is taken to zero, in many situations, this point is the actual ground or earth.

Ground Fault Circuit Interrupter or GFCI

A device whose function is to interrupt the electric circuit to the load when a fault current to ground exceeds a predetermined value,H

H Rating (switches)

Denotes a non-inductive resistive rating.

High Inrush

Loads that require a higher amount of current or amperage when first turned on, compared to the amount of current required to continue running. An example of high inrush load is a light bulb, which may draw 20 times its normal operating current when first turned on. Some manufacturers refer to this as lamp load. Other examples of loads that have high inrush are switching power supplies (capacitive load) and motors (inductive load).

Horsepower (hp)

Motors are rated in horsepower (HP) or fractions of horsepower (1/4, 1/3, 1/2, etc.) Mechanically, One horsepower (1HP) is equal to 33,000 pounds being moved 1 foot in 1 minute (or 33,000ft-lb/min). One horsepower (1HP) is also equal to 746 watts of electrical power.I

Independent Lamp

A lamp or lamps powered by a voltage source not controlled by the switch or circuit breaker action.

Inductive Load

Usually a device that moves and normally includes electric magnets, like an electric motor. Examples of inductive loads include: power drills, electric mixers, fans, sewing machines, vacuum cleaners. Transformers also result in inductive loads.

Inrush

The amount of current a load takes on initial start up. This can be many times it's normal operating current but is usually of very short duration.

Instantaneous Trip

Indicates that no intentional delay is purposely introduced in the opening time of a protector.

Insulation Resistance

The resistance between two normally insulated parts measured at a specified high DC potential (megohm range). Also referred to as Leakage Resistance.

Interrupting Capacity

The maximum fault current that can be interrupted by a protective device without failure of the device. Often referred to as Rupture Capacity. Circuit breakers are also rated according to the level of fault current they can interrupt. When applying a circuit breaker, one must be selected which can sustain the largest potential short circuit current that can occur in the selected application.