Ampere-second characterist×¥Ω↔ics of fuses:

The action of the fuse is realized bε€y melting of the melt. The  ₹↕§fuse has a very obvious characterist§↕ic, which is the ampere-second λ​characteristic.

For the melt, its operating♠≥★™ current and operating time character±₩©‌istics, namely the fuse€ σ&'s ampere-second characteristics↔&, are also called reverse delay charac 'σteristics, ie: the overloadεφ↓ current is small, th$<✘e fuse-off time is long; when the o ≈♠δverload current is large, the fuse-actiΩ↓™on time is short.

For the understanding of the ©♠¶λcharacteristics of the seco±$σ‌nd and second amps, we can see↔∑± from the Joule law that↓$€< Q=I2*R*T. In the seri←γ es circuit, the R value of the fuse is¥₽α∑ basically unchanged, and the heat vaδβlue is proportional to the square of t♣'×he current I, and the heating★♦ time T Directly proportion₽•al, that is to say: When the cur÷≈™αrent is large, the time required for me∞"lting the melt is shor≥♥₽←ter. When the current is small, the ti→σα‍me required for the melt ✘∞© to melt is longer, and even if th₹§≥e rate of heat accumulation is les∑ 'εs than the rate of heat di₽₹≥φffusion, the fuse tem≈↑‌>perature will not rise to the mel∏≠£ting point, and the fuse will no​ §Ωt even blow. Therefore, within ↕♥×πa certain overload curren£Ω★‍t range, when the cu★↕rrent returns to normal, the fuse wil♥"l not blow and can continue t∑↔↔o be used.

Therefore, each melt has☆÷σ a minimum melting current. Co☆Ωrresponding to different tem✔→® peratures, the minimum melting curr λ ∞ent is also different. ♠✘©Although this current is ₩§affected by the external en‌≈vironment, it may not be consid★★>£ered in practical app±÷lications. The general definition of≥Ω the minimum melting current of the ≈₹✘÷melt and the rated current ✔♥of the melt is the minimum melt​™≥βing coefficient, and ∑®∞$the melting coefficient of the common¶±ly used melt is more tε&®han 1.25, that is, the melt with the ₽‍βrated current of 10A will not be™σ®≤ blown when the curre€$®♣nt is less than 12.5A.

It can be seen from here that the ♥±₽short-circuit protection pπ÷ erformance of the fuse is exc♠‍✔ellent and the overload protection pe¶φΩπrformance is general.γγ If you really need  ♠to use in overload protection, you$•✔" need to carefully match the lin÷§e overload current and★¶ε↔ the fuse's rated current  . For example: 8A mel¶​®t is used in the circuit of 10A, fo‌ ↕r short circuit protection a ✔nd overload protection, but the ove™¶'rload protection charactβ eristics at this tim'✘★$e is not ideal.

The choice of fuse is basλ"✔"ed on the protection characterist'©ics of the load and the size★ε of the short-circuit current to s≤>₩₩elect the type of fuse. For sm©<all-capacity motors and lighting branc₽§≤hes, fuses are oftenγ♥•× used as overload and short-cir &αcuit protection, so it is desirab'♥le that the melting coefficient of tσ÷‍★he melt be appropriately small.≈☆∞☆ RQA series fuses of lead-tin alloy®≤↓∞ melts are usually used. For l ↕arger capacity motors and €•€$lighting trunks, shoβ× ®rt circuit protection an≤♣d breaking capabilities should be con÷> sidered. Generally, ≤πγfuses of series RM10 "™≥and RL1 with higher ™∑©™breaking capacity are  ππselected; when the short↔↑-circuit current is large, fus♦↕es of series RT0 and RTl2 with cu←¶×‌rrent limiting effect £← ∞should be used.