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IEC 60269 unifies the electrical characteristics of fuses that are dimensionally interchangeable with fuses built to earlier British, German, French or Italian standards. [2] The standard identifies application categories which classify the time-current characteristic of each type of fuse. The application category is a two-digit code.
The time and current operating characteristics of fuses are chosen to provide adequate protection without needless interruption. Wiring regulations usually define a maximum fuse current rating for particular circuits. A fuse can be used to mitigate short circuits, overloading, mismatched loads, or device failure. When a damaged live wire makes ...
Instantaneous overcurrent requires that the current exceeds a predetermined level for the circuit breaker to operate. Time overcurrent protection operates based on a current vs time curve. Based on this curve, if the measured current exceeds a given level for the preset amount of time, the circuit breaker or fuse will operate.
Miniature circuit breaker (MCB)—rated current up to 125 A. Trip characteristics normally not adjustable. Thermal or thermal-magnetic operation. Breakers illustrated above are in this category. Molded Case Circuit Breaker (MCCB)—rated current up to 1,600 A. Thermal or thermal-magnetic operation. Trip current may be adjustable in higher-rated ...
Breaking current may be stated in terms of the total current or just in terms of the alternating-current (symmetrical) component. Since the time of opening of a fuse or switch is not coordinated with the reversal of the alternating current, in some circuits the total current may be offset and can be larger than the alternating current component ...
Electromechanical protective relays operate by either magnetic attraction, or magnetic induction. [9]: 14 Unlike switching type electromechanical relays with fixed and usually ill-defined operating voltage thresholds and operating times, protective relays have well-established, selectable, and adjustable time and current (or other operating parameter) operating characteristics.
AFCI circuit breakers include a standard inverse-time circuit breaker but provide no specific protection against "glowing" connections (also known as a high resistance connection), high line voltages, or low line voltages. An AFCI does not detect high line voltage caused by an open neutral in a multiwire branch circuit.
The standard specifies breaking time versus current characteristics only for 3 A or 13 A fuses. For 3 A fuses: 0.02–80 s at 9 A, < 0.1 s at 20 A and < 0.03 s at 30 A. For 13 A fuses: 1–400 s at 30 A, 0.1–20 s at 50 A and 0.01–0.2 s at 100 A.