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Glossary
GLOSSARY OF TERMS
Find the definitions for a wide range of electrical concepts and terms used within the industry and within this site.
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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.
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.
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.
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.
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.
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.
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)
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 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.
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.
L Rating (switches)
Denotes the ability of a switch to handle the initial high inrush of Tungsten Filament Lamp on AC Voltage only.
LED
Light Emitting Diode
Let-through Current
The actual fault current passing through a protective device as compared to the current available to the device.
Life Expectancy (Useful Life)
Depends upon the end life criteria for a specific application. In order to determine you failure criteria, the following parameters should be known: dielectric strength, duty cycle, mechanical breakdown, contact resistance, insulation resistance, operating force. Life expectancy is normally experienced in minimum switch cycles before failure.
Load (Electric)
The amount of electric power delivered or required at any specific point or points on a system. The requirement originates at the energy consuming equipment of the consumers.
Make-Before-Break
Switches that complete a new circuit before breaking an old one.
Maintained Switch
A switch that maintains the mode or position to which it is actuated.
Micro Gap
A symbol appearing as a part of the switch rating that indicates a contact gap of less than 3 millimeters.
Momentary Switch
A switch that automatically returns to its original or at rest position.
Normally Closed
Often abbreviated N.C., indicates that the circuit is closed when the switch is not operated. Activation of the switch causes the circuit to open.
Normally Open
Often abbreviated N.O., indicates that the circuit is open when with switch is not operated. Activation of the switch causes the circuit to close.
Ohm
The unit of measurement of electrical resistance. The resistance of a circuit in which a potential difference of 1 volt produces a current of 1 ampere.
Ohm's Law
The mathematical expression which shows the relationship between current (I), voltage (V), and resistance (R). Ohm's Law shows that as resistance gets higher, the current gets smaller, and vice versa.
R = V/I
I = V/R
V = IR
Open Circuit
An electrical circuit that will not conduct electricity because either air, or some other insulator has stopped or broken the flow of current in the loop.
Operating Force
Also known as Actuation Force, the force required to transfer a switch from one position to another.
Overload Current
The current value in excess of the rated current of the protective device.
Pole
The number of completely separate circuits that can be active through a switch or simultaneously protected by a circuit breaker at any one time.
Push-On/Push-Off
An alternate action switch, often used on lamps, vacuum cleaners, etc. When pushed, the circuit closes. When pushed again, it opens. Often called 'Push-Push.
Quick Break/Quick Make
Switches designed to make or break circuits in less than 5 milliseconds to make or break. Recommended for use on DC circuits.
Resistance
The opposition a conductor offers to current.
Resistive Load
Load that offers resistance to the flow of current. Examples of resistive loads: electric heaters, ranges and ovens, toasters, and irons. If the device is supposed to get hot and doesn't move, it's mostly likely a resistive load.
Short Circuit
A connection of comparatively low resistance accidentally or intentionally made between points on a circuit between which the resistance is normally much greater.
Single Break / Single Make
Contacts that open and close a circuit at only one place.
Single Pole - SP (switches)
A switch device that opens, closes, or changes the connection of a single conductor in an electrical circuit.
Single Throw (ST)
A switch that opens, closes or completes a circuit at only one of the extreme positions of its actuator.
Slow Break/Slow Make
Switches designed to make or break circuits within e 8-12 milliseconds. Typically used for AC applications.
Snap-Action
Non-teasable switch action having unstable equilibrium so that it must be either 'ON' or 'OFF'. Can also be referred to as 'Push-Push.'
Terminal
1) The point at which electrical connections are made. 2) The mechanical device at such a point in a circuit, as at the end of a wire or cable, by means of which an electrical connection may be made.
Time Delay
The introduction of an intentional delay to the opening function of a protective device.
Total Clearing Time
The time elapsing form the initiation of overload current to final current interruption.
Ultimate Trip Current
The minimum value of current that will cause tripping of a protective device.
Volt (V)
The electromotive force which, if steadily applied to a circuit having a resistance of one Ohm, will produce a current of one Ampere.
Voltage
Electric potential or potential difference expressed in volts
Voltage Drop
A conductor's voltage reduction due to resistance.
Voltage of a Circuit
The electric pressure of a circuit in an electric system measured in volts. It is generally a nominal rating based on the maximum normal effective difference of potential between any two conductors of a circuit.
Voltage Rating
The maximum voltage at which a device is designed to operate.
Voltage Trip
A protective device that is factory calibrated to trip at a predetermined voltage value.
Watt
The unit of electrical power required to do work at the rate of one joule/second or the power consumed when one ampere flows with one volt applied to a circuit.
Wiping Action Contacts
Self-cleaning contacts that wipe or slide against each other when opening or closing a circuit.
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