The I 2 t characteristic of the short time function determines the delay type. ... A typical fuse time-current curve is shown below. Replacement is must after completed operation. In fact a 13A fuse will allow a current of 20A to pass indefinitely without blowing. Kearney offers six types of fuse links with a wide range of time-current characteristics (refer to Table 1). Higher the ambient temperature, the hotter the fuse will operate and it shorter its life. https://electrical-engineering-portal.com/fuse-characteristics-protection-circuits and other fuses. Understanding overcurrent protection device characteristics is very important in a protection coordination study. The grey shaded area is the point where the fuse is designed to operate. The time-current characteristics of fuses are affected by ambient temperature. Figure 3. The speed ratio of all fuse link sizes 100 A and below is the ratio between the current that melts the fuse in 0.1 seconds to the current that melts the fuse in 300 seconds. Replacement & post-operation: Fuse can be used only once per operation as it is self destructive. BASIS-These fuse links are tested in accordance with the ... than 200% of fuse-link ampere rating, and the minimum melting and total clearing curves are based on tests starting with the fuse link at an ambient temperature of 25°C (77°F) and no initial load. Characteristic Curve: Fuse characteristic curve shifts because of the ageing effect. I 2 t IN will result in an inverse-time delay that resembles the time/current characteristics of fuses. MICRO3 Fuse Time-Current Characteristics 3 5 7.5 10 15 Time-Current Characteristic Curves Blade Fuses Dimensions Dimensions in mm Temperature Rerating Curve *Component Level Temperature = the maximum ambient temperature that a single fuse will survive. The higher the ratio, This is similar to the long time function except with a much faster delay. For example, Littelfuse’s 383 series - TR5® time-lag 300V rated fuses have time-current characteristics as shown by the below graph. It is related to the let through energy I 2 t characteristics.. TC curves… A fuse’s time-current characteristics can help. The selectivity limit current is the value at which the let-through energy I 2 t of the circuit-breaker exceeds the pre-arcing I 2 t of the fuse (curve or value provided by the manufacturer).. Circuit breaker characteristic curve doesn’t shift. This does not factor-in the heat from a populated fuse Melting Integral I2t Rating: ... Time-Current Characteristics curve. Also, fuses have an inverse time-current characteristic, which means the greater the overcurrent, the faster they interrupt. 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