The measurement of intensity of rate of flow of electrons in an electric circuit.One ampere is the amount of current that will flow through a resistance of one ohm under a pressure of one volt.
The current carrying capacity of a fuse. When a fuse is subjected to a current above its ampere rating, it will open the circuit after a predetermined period of time.
Ampered Squared Seconds (ixixt)
The measurement of heat energy developed within a circuit duting the fuse`s clearing. It can be expressed as melting-ixixt,arcing-ixixt,or the sum of them as clearing-ixixt.”i” stands for effective let-through current (RMS),which is squared, and “t” stands for time of opening, in seconds.
The amount of time from the instant the fuse link has melted until the overcurrent is interrupted, or cleared.
The rating which defines the fuse`s ability to safely interrupt and clear short circuits. This rating is much greater than the ampere rating of a fuse.The NEC defines interrupting rating as “The highest current at rated voltage that an overcurrent protective device is intended to interrupt under standard test conditions.”
The total time during the beginning of the overcurrent and the final opening of the circuit at rated voltage by an overcurrent protective device. Clearing time is the total of the melting time and the arcing time.
A fuse operation relating to short circuits only. When a fuse operates in its current limiting range, it will clear a short circuit in less than 1/2 cycle. Also, it will limit the instantaneous peak let-thru current to a value substantially less than that obtainable in the same circuit if that fuse were replaced with a solid conductor of equal impedance.
Fast Acting Fuse
A fuse which opens on overload and short circuits very quickly.This type of fuse is not designed to withstand temporary overload currents associated with some electrical loads.
High Speed fuses
Fuses with no intentional time-delay in the overload range and designed to open as quickly as possible in the short circuit range. These fuses are often used to protect solid state devices. For INTERRUPTING RATING see..BRAKING CAPACITY
The amount of time required to melt the fuse. Link during a specified overcurrent. (See Arcing Time and Clearing Time).
The unit of measure for electric resistance. An ohm is the amount of resistance that will allow one ampere to flow under a pressure of one volt.
The relationship between voltage, current, and resistance, expressed by the equation E=IR, where E is the voltage in volts,I is the current in apmperes, and R is the resistance in ohms.
A condition which exists on an electrical circuit when the normal load current is exceeded. Overcurrents take on two seperate characteristics–overloads and short circuits.
Can be classified as an overcurrent which exceeds the normal full load current of a circuit. The current does not leave the normal current carrying path of the circuit–that is, it flows from the source, through the conductors, through the load, back through the conductors, to the source again.
Peak Let-Thru Current IP
The instantaneous value of peak current let-thru by a current limiting fuse,when it operates in its current limiting range.
An electrical which is characteristic of not having any significant inrush current. When a resistive load is enrgized, the current rises instantly to its staedy state value, without first rising to a higher value.
The R.M.S.(root-mean-square) value of any periodic current is equal to the value of the direct current which, flowing through a resistance, produces the same heating effect in the resistance as the periodic current does.
An overcurrent which exceeds the normal full load current of a circuit by a factor many times (tens,hundreds,or thousands greater). The overcurrent also leaves the normal current carrying path of the circuit–it takes a “short cut” around the load and back to the source.
A fuse with a built in delay that allows temporary and harmless inrush currents to pass without opening, but is so designed to open on sustained overloads and short circuits.
The maximum open circuit voltage in which a fuse can be used, yet safely interrupt an overcurrent. Exceeding the voltage rating of a fuse impairs its ability to clear an overload or short circuit safely.
FF = Super quick acting
F = Quick acting
M = Medium time lag
T = Time lag
TT = Super time lag