How does a polymer self-replicating fuse work?
Polymer self - fuses consist of a polymer matrix and carbon black particles that conduct electricity. Because the polymer self - fuses are conductors, an electric current passes through them. When an overcurrent passes through the polymer to self-fuse, the heat generated (I2R) causes it to expand. The carbon black particles will then separate, and the resistance of the polymer self-replicating fuse will rise. This causes the polymer to generate heat faster and expand larger, further increasing resistance. When the temperature reaches 125°C, the resistance changes significantly, resulting in a significant decrease in current. The small current flowing through the polymer's self-fusing wire is sufficient to keep it at this temperature and in a high resistance state. When the fault is cleared, the polymer self-fuses shrink back to their original shape to reattach the carbon black particles, lowering the resistance to the required holding current. This process can be repeated many times.
What's the difference between Rmin, Rmax and R1max?
Rmin specifies a minimum resistance for ANDU's polymer self-re-fuses. This resistance determines the minimum operating current for the polymer self-re-fuses. Rmax provides the maximum resistance specified for polymer self - refilling fuses supplied by ANDU. R1max is the maximum resistance that the polymer self-fusing fuse should reach after operation, and its resistance value determines the maximum holding current of the polymer self-fusing fuse. As the polymer refuses, the resistors supplied by ANDU increase their resistance (greater than or equal to Rmin and less than or equal to Rmax) to less than or equal to R1max
What is the voltage drop on the polymer self - fuses?
It depends on the circuit. Generally speaking, the voltage drop can be calculated if the resistance and equilibrium current are known. The maximum voltage drop of polymer fuses is calculated by using resistance R1max. The typical pressure drop can be the resistance Rmax or the average of Rmin and R1max if Rmax is not provided. If Iop is the normal operating current and Rps is the resistance of the polymer self-replying fuse (R1max, (Rmax, or (Rmin + R1max) /2)), the voltage drop across the polymer self-replying fuse in the circuit is: Vdrop = Iop x Rps
Can polymer fuses be connected in series?
It doesn't make sense. Because one of them always moves first, and the others don't protect the circuit.
How to calculate the resistance of polymer self - fuses in action state?
The resistance of the polymer self - fuses operating state depends on the specific type and the voltage and power on it. It can be calculated by the following formula: Rt = V2/Pd?
How many times can a polymer self-restoring fuse operate under maximum voltage and impulse current?
Each polymer self - fusing wire has a specific operating voltage and can withstand a specific impulse current. UL specifies that polymer self-regenerating fuses must still exhibit PTC effects after 6,000 operations. For SN/SF polymer self-restoring fuse used in communication equipment, the performance parameters are still in the original range after at least ten to hundreds of operations under the maximum voltage. Designers should be aware that polymer fuses are intended for protection, not for situations where their constant action is considered normal.
How quickly does the polymer recover from the fuses?
The time it takes for the polymer to return to its low resistance state after the action of the polymer self-re-fuse is affected by the type of polymer self-re-fuse; How it is affixed or secured; Ambient temperature; The internal cause and duration of an action. In general, most polymer self-restoring fuses will recover in minutes, although many will recover in seconds.
How long can a polymer self-replicating fuse stay in action without damage?
UL specifies that polymer self-regenerating fuses must remain at maximum voltage for 1000 hours without losing their PTC characteristics. The longer a polymer self-resetting fuse is in the operating state, the more likely it is that its resistance value will not recover and thus may not meet its original definition. The amount of time each polymer self-resetting fuse can hold varies with the event and type of failure.
Can polymer fuses be graded according to resistance?
Some of our polymer self - fuses are graded according to the resistance value and then provided to the user. Polymer self - restoring fuses, such as SF250, SD250 and SF600, are mainly used in the field of communication.
What are the effects on the encapsulation of polymer self-reproducing fuses?
In general, although some customers have successfully packaged our products, we do not advocate it. In packaging must pay attention to the choice of materials and bending packaging method. If the packaging material is too hard, it will not allow the polymer self-replying fuse to expand as designed, so that it will not work as designed. Even if the packaging material is soft, the heat transfer characteristics of polymer self-fuses will be affected, making the polymer self-fuses behave differently than the design requirements.
What is the effect of pressure on polymer fuses?
Pressure will affect the electrical properties of polymer self - fuses. If there is too much pressure during the operation to limit the expansion of the polymer self-fusing fuse, the polymer self-fusing fuse will not operate as required.
How does the appearance of a sample determine the type of polymer self-replicating fuse?
Most polymer self - fuses will bear the logo and model number. A variety of standard polymer self-renewing fuse product models are listed in the company's product description. In addition, the company also tailors products to meet their special requirements.
What is the maximum ambient temperature at which polymer self - fuses work?
The polymer self-replicating fuse in working condition depends on the product type. For most of our products, this range goes up to 85°C, some as high as 125°C (e.g. SN/SF), and some as low as 70°C (LP-CW). Polymer self - reflow fuses in non-working state are somewhat resistant to shorter reflow temperatures (LP-SM, LP-MSM, SD).
Can polymer self - fuses self - recover? How to self-recover? How fast?
Yes, once the fault has been cleared and the polymer self-regenerating fuse has had a chance to cool, it will self-regenerating. Cooling allows carbon black particles to contact and rebond, reducing electrical resistance. Typically, polymer self-fuses are cooled by cutting off the energy supply to the device being protected, cutting off the fault current and allowing the polymer self-fuses to cool. Polymer self-replicating fuses should be distinguished from bimetallic devices that are also capable of self-replicating. Even if the fault event is not cleared, the typical bimetallic device will self-recover, switching between the fault event and the protected state that may damage the device. Polymer fuses remain in a high resistance state until the fault is cleared. The time required for polymer self-rewinding to a low resistance state depends on a number of factors: the type of polymer self-rewinding fuse; How it is affixed or secured; Ambient temperature; The internal cause and duration of an action. In general, most polymer self-restoring fuses will recover in minutes, although many will recover in seconds.
Can polymer fuses undergo state transitions? How do you keep things the same?
Polymer self - fuses do not transition between normal and operational states when a fault event has not been eliminated. When the polymer self - fuses operate, the resistance goes from low to high. At high resistance, a small amount of fault current still exists. This small fault current is sufficient to keep it in a high resistance state. When the fault is cleared, the polymer self - fuses can be cooled back to a low resistance state.
What is the difference between IH and IT? Why the difference?
IH is the highest current (from 20°C to 25°C depending on the temperature of the product) in still air without triggering resistance spikes, i.e. the highest operating current at room temperature. IT is the minimum current (from 20°C to 25°C depending on the temperature of the product) when the polymer self-fuses operate in still air, i.e. the minimum fault current at room temperature. For most of our products, the IT to IH ratio is 2:1, but for some products it can be as low as 1.7:1, and for others it can be as high as 3:1. The difference in material and production method and the change in resistance after operation will determine this ratio.
Polymer self - fuses self - fuses when?
Polymer self - fuses self - recovery is a function of current, voltage and temperature. Polymer self-replicating fuses will often start self-replicating at temperatures below 90°C (it can be said that self-replicating fuses below 80°C complexes have self-replicating)
What is the difference between polymer fuses and ordinary fuses and other circuit protection devices? How do polymer fuses protect circuits with overvoltage bearing devices?
The most obvious difference between polymer fuses and ordinary fuses is that polymer fuses are self-renewing. Although both can provide overcurrent protection, polymer self-resetting fuses can provide multiple overcurrent protection whereas normal fuses, once blown, must be replaced to allow the circuit to function properly. Polymer self-fuses behave somewhat like time-delay fuses, both of which need to take their own heat dissipation into account, but polymer self-fuses do not dissipate in accordance with I2t as time-delay fuses do, because polymer self-fuses do not work at the beginning. Polymer fuses do not differ from bimetallic fuses in that they are self-renewing. Bimetallic fuses are self-renewing while the fault persists. When it operates, it generates a large voltage and reconnects faults that may damage the equipment. Polymer fuses remain in a high resistance state until the fault is rectified. Polymer fuses differ from ceramic fuses in their initial resistance, response time to failure, and size. Both are self-replicating, but polymer self-replicating fuses are faster because of their smaller size than ceramic self-replicating fuses with the same holding current. Polymer fuses used in combination with load-bearing overvoltage devices are commonly used in communications. For many failure events, overvoltage bearing devices such as thyristor, gas discharge tubes, or diodes can provide protection. Polymer self-resetting fuses can protect these overvoltage protectors in certain failure events, and of course polymer self-resetting fuses can also provide overcurrent protection.
Will the polymer return to its original state when fuses are operated and expanded?
The polymer self-fuses in action expand, cool and self-fuses and return to their original size and shape. It doesn't go back to its original value but it goes back to a value that fits its definition.
What is the highest temperature that polymer self - fuses can reach?
Polymer self-refilling fuses can reach a maximum surface temperature of 150°C, but the typical surface temperature is 110°C.
RF restorable fuse (short for RF) is made of polymer and conductive material mixed, serialized in the circuit, normally, RF is low resistance state, to ensure the normal operation of the circuit; Under abnormal circumstances, RF resistance value can rise to more than 106 times the original resistance value in a very short time to "disconnect" the line, to ensure that the relevant components in the line are not burned. The characteristics are as follows:
Self-recovery: after the exception or fault is removed, RF will recover from high resistance to low resistance, so that the circuit smooth normal work;
(2) Fast action: when the abnormally large current through RF into the circuit, RF resistance value increases sharply, rapid action;
(3) Long life: anti-aging, antioxidant and other additives are added to RF raw materials, and the use of crosslinking section to make RF performance unchanged for a long time;
(4) High reliability: RF working for a long time after the resistance value is unchanged or slightly decreased, high conductivity so that RF long-term work will not break;
⑤ Suitable for all kinds of working environment: in the temperature 100℃, humidity 100% or -10℃ environment, RF performance unchanged.