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Self-recovery fuse knowledge solution

Release time:

2024-03-07

The storage period of polymer PTC thermistor, also called self-recovery fuse, has no time limit. It can be stored for a long time under normal storage conditions of electrical components. If exposed to excessive humidity or high temperature, the performance of some specifications may change, such as the solderability of tin and lead.

1. Storage of self-recovery fuse

　How fast can a polymer PTC thermistor reset automatically?

In general, as long as the voltage loaded on both ends of the thermistor is removed, the thermistor can be reset; but if the external environment temperature is very high (such as 150 ℃), the thermistor cannot be reset. The time required for the polymer PTC thermistor to return to the low resistance state depends on many factors: the type of product, the assembly form, the structure, the outside temperature, the duration of the open state, etc. Generally, the reset time is less than a few minutes, and in some cases it only takes a few seconds for the thermistor to reset.

　　3. Can polymer PTC thermistor be cleaned?

Many common electrical component cleaning agents can be used to clean the polymer PTC thermistor, but some cleaning agents may damage the performance of the thermistor. It is best to test or consult our company before cleaning.

　4. Can polymer PTC thermistors be used in parallel?

You can. The main advantage of this is that the resistance can be reduced and the holding current can be increased.

5. Can polymer PTC thermistors be used in series?

There is no benefit to this for most uses, and it is not practical to do so. Because there is always a polymer PTC thermistor disconnected first, so other thermistors simply do not play an additional protective role.

6. What is the failure mode of polymer PTC thermistor?

The typical failure mode of polymer PTC thermistor is that the room temperature resistance of the product becomes too large, and the holding current of the product will become smaller. Thermistors must meet two criteria:

(1) It can be broken for 6000 times and still has PTC capability;

(2) Keep the open circuit state for 1000 hours and still have PTC capability.

In order to obtain UL certification. If the thermistor exceeds its rated voltage or current during a fault condition, or the number of open circuits exceeds the UL detection requirements, the thermistor may deform and burn.

　7. How many times can a polymer PTC thermistor work at maximum voltage or breaking current?

Each polymer PTC thermistor has a rated operating voltage and can withstand a rated breaking current in the event of a fault. To obtain UL approval, the switch must be able to open 6000 times and maintain PTC properties. For thermistors used in communication equipment (switches, training rack security units, etc.), the service life of the product is specified in the line label. This requires that the switch can return to the initial characteristic value as few as dozens of times and as many as hundreds of times. Designers should keep in mind that the polymer PTC thermistor is used to prevent faults instead of using its open circuit state as its normal state.

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