电气英语证书考试(pec)-电气工程专有名词3.doc

电气英语证书考试电气英语证书考试(PEC)-Glossary of Electrical Engineering Terms3oAmpereThe measurement of intensity of rate of flow of electrons in an electric circuit. An ampere is the amount of current that will flow through a resistance of one ohm under a pressure of one voltoAmpere RatingThe 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 timeoAmpere Squared Seconds, l2tThe measure of heat energy developed within a circuit during the fuse’s clearing. It can be expressed as “Melting l2t”, “Arcing l2t” or the sum of them as “Clearing l2t”. “l” stands for effective let-through current (RMS), which is squared, and “t” stands for time of opening, in seconds.oArcing TimeThe amount of time from the instant the fuse link has melted until theovercurrent is interrupted, or clearedoCartridge FuseA fuse consisting of a current responsive element inside a fuse tube with terminals on both endsoClass CC Fuses600V, 200,000 ampere interrupting rating, branch circuit fuses with overall dimensions .Their design incorporates a rejection feature that allows them to be inserted into rejection fuse holders and fuse blocks that reject all lower voltage, lower interrupting rating fuses.oClass G Fuses20A@600VAC, 25-604@480VAC, 100,000 ampere interrupting rating branch circuit fuses that are size rejecting to eliminate over fusing. These are available in ratings from 1 amp through 60 amps. Class H Fuses 250V and 600V, 10,000 ampere interrupting rating branch circuit fuses that may be renewable or non-renewable. These are available in ampere ratings of 1 amp through 600 amps.oClass J FusesThese fuses are rated to interrupt a minimum of 200,000 amperes AC. They are labelled as “Current-Limiting”, are rated for 600 volts AC, and are not interchangeable with other classes.oClass K FusesThese are fuses listed as K-1, K-5, or K-9 fuses. Each subclass has designated I2t and lp maximums. These are dimensionally the same as Class H fuses, and they can have interrupting ratings of 50,000, 100,000, or 200,000 amps. These fuses are current-limiting. However, they are not marked “current-limiting” on their label since they do not have a rejection feature.oClass L FusesThese fuses are rated for 601 through 6000 amperes, and are rated to interrupt a minimum of 200,000 amperes AC. They are labeled “current-limiting” and are rated for 600 volts AC. They are intended tobe bolted into their mountings and are not normally used in clips. Some Class L fuses have designed in time-delay features for all purpose use.oClass R FusesThese are high performance fuses rated 1/10 – 600 amps in 250 volt and 600 volt ratings. All are marked “current-limiting” on their label and all have a minimum of 200,000 amp interrupting rating. They have identical outline dimensions with the Class H fuses but have a rejection feature which prevents the user from mounting a fuse of lesser capabilities (lower interrupting capacity) when used with special Class R Clips. Class R fuses will fit into either rejection or non-rejection clips.oClass T FusesAn industry class of fuses in 300 volt and 600 volt ratings from 1 amp through 1200 amps. They are physically very small and can be applied where space is at a premium. They are fast-acting and time-lag fuses, with an interrupting rating of 200,000 amps RMS.oClasses of FusesThe industry has developed basic physical specifications and electrical performance requirements for fuses with voltage ratings of 600 volts or less. These are known as standards. If a type of fuse meets the requirements of a standard, it can fall into that class. Typical classes are K, RK1, RK5, G, L, H, T, CC, and JoClearing TimeThe total time between 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 timeoCurrent-LimitationA 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-through 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.oOhmThe 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.oDual-Element FuseFuse with a special design that utilizes two individual elements in series inside the fuse tube. One element, the spring actuated trigger assembly, operates on overloads up to 5-6 times the fuse current rating. The other element, the short-circuit section, operates on short-circuits up to its interrupting rating.oElectrical LoadThat part of the electrical system which actually uses the energy or does the work required.oFast Acting FuseA fuse which opens on overload and short circuits very quickly. This 。