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Many people do not know much about the self-recovery fuses, do not know how to apply, and do not know how CPTC self-restoring fuses, PTC thermistors and PPTC self-recovery fuses are different.
Large capacity electronics for your answer:
Since the recovery fuse is a kind of over current protection device, is a kind of macromolecule organic polymer in high pressure, high temperature, curing reaction conditions, mixed with conductive particles, through special process. Is another kind of inorganic ceramic chip ceramic PTC thermistor, referred to as "CPTC, traditional fuse over-current protection, can protect only once, in the need to change, since the recovery fuse with flow overheating protection, automatic double function recovery. Have over-current protection function on the habits of PPTC (PolyerPositiveTemperature Coefficent) and CPTC called self recovery fuse.
Principle of self-restoring fuse:
Since the recovery fuse is a thermistor with PTC effect, in the normal state offline since the recovery fuse on the current the heat energy produced is small, when the line short circuit or overload occurs, the large current flows through the recovery fuse produce heat to make the recovery of fuse resistance increases sharply, form a high impedance state, working current rapidly decreases, and thus to restriction and protection circuit. When the fault is removed, the self-restoring fuse is recooled, and the self-restoring fuse is restored to a low resistance state, thus completing the protection of the circuit without manual replacement.
Action principle:
Since the recovery action principle of the fuse is a kind of dynamic balance of energy, due to the current through the element since the recovery fuse series relations to generate heat, since the recovery fuse series of heat to send out all or part of the environment, and not send out heat will improve the recovery of the temperature of the fuse series components. The temperature at normal work is low, resulting in a balance of heat and heat emission. Components in low resistance state, since the recovery fuse series not action, since the recovery fuse series current through the element since the recovery fuse series when increase or environmental temperature, but if to produce heat and heat balance, since the recovery fuse series still don't. When the current or ambient temperature increases, the self-restoring fuse series will reach a higher temperature. If continue to add to the current or ambient temperature, the heat generated by the distributed will be greater than the quantity of heat, make self recovery fuse series element temperature jump, at this stage, the temperature of the small changes can lead to the large increase in value, then the recovery fuse series components in a high resistance to protect state, the increase of impedance limits the current, the current in a short time fell sharply, thus protecting circuit equipment from damage, as long as the heat generated by the applied voltage enough since the radiate heat recovery fuse series component, under a state of change since the restoration of the fuse series components could have been in a state of action (high resistance). When the applied voltage disappears, the self-restoring fuse series can be automatically restored.
Classification of self-restoring fuse:
The self-restoring fuse can be divided into polymer-polymer PPTC and ceramic CPTC two kinds of self-restoring fuse, which can be divided into two types: lead plug and SMD patch. Can also according to the voltage divided into 600 v, 250 v, 130 v, 120 v, 72 v, 60 v, 30 v, 24 v, 16 v, 6 v plug-in polymers such as self-healing fuse. The main advantages of polymer PPTC are: the normal temperature and zero power resistance can be made very small, and the large current product has only a few milliohms, which can be neglected and relatively small in the road power consumption. Vulnerability can be in series in the circuit for over-current protection, temperature fuse, speed, resistance mutations in several orders of magnitude, ms heat capacity is small, short recovery time, impact resistance, recycled protection up to 8000 times. PTC can be used as temperature fuse, so in the circuit to a certain extent the temperature fuse performance and temperature fuse function. The dual protection function of overcurrent protection and over-temperature protection is achieved in the circuit.
Ceramic CPTC the main advantages of the manufacture is easy, relatively cheap, but resistance is big, big volume, loss is big, the road dozens to several thousand Ω range, suitable for small current over-current protection, when high temperature overheating easy appear negative resistance effect (resistance smaller), slow speed of protection, the order of hundreds of ms, large heat capacity, long recovery time. Application range is relatively narrow, such as can not be applied to rapid protection circuit, auto harness protection, PCB line mark protection and so on, the more applied in the heating devices, in some small signal circuit, don't need to consider the loss can be chosen.
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