As an electronic component, the core function of a varistor lies in its sensitivity to voltage, that is, within a certain range of current and voltage, its resistance value will change as the voltage changes. This characteristic makes varistor an indispensable component in circuit protection, especially in preventing voltage surges and overload protection. In order to deeply understand the working principle and application of varistor, this article will conduct a detailed analysis of the characteristic parameters of varistor and discuss its performance in derating.
First of all, one of the core characteristic parameters of a varistor is the varistor voltage UN (U1mA). This parameter is usually defined by the voltage present when a 1mA DC current passes through the varistor. This voltage marks the critical point at which the varistor begins to conduct, and is usually represented by U1mA. It is worth noting that the error range of varistor voltage is generally ±10%. This error range plays a decisive role in the protection of equipment in practical applications. During testing and actual use, a 10% drop in varistor voltage is used as an important criterion for varistor failure, which is crucial to ensuring long-term stable operation of the equipment.
Secondly, the continuous operating voltage UC, that is, the AC or DC voltage value that the varistor can safely withstand for a long time, is another key parameter. This parameter ensures the safety and reliability of the varistor in daily use. Its value generally has a certain proportional relationship with the varistor voltage. Usually the AC continuous working voltage is about 0.64 times the varistor voltage, and the DC continuous working voltage is about 0.83 times. This proportional relationship is crucial for designing a safe circuit protection system, which ensures the stability and reliability of the varistor within the normal voltage range.
Next, the throughput (inrush current) IP is a parameter that describes the maximum inrush current peak that the varistor can withstand. This parameter is crucial for evaluating the performance of the varistor under extreme conditions. Technical specifications usually give the maximum current value that the varistor can safely withstand an 8/20μs wave shock. The setting of this parameter is based on an important standard: the change rate of the varistor voltage after an impact shall not be greater than 10%. This standard ensures that the varistor can still maintain its basic protection function even after suffering a sudden current impact. .
In addition, the clamping voltage (limiting voltage) VC refers to the voltage value present on the varistor under a given inrush current condition. This parameter is directly related to the efficiency of the varistor protection circuit, that is, in actual use, when the applied impulse current increases, the limit voltage will also increase accordingly. Through the V-I curve provided by the product, you can intuitively understand the limiting voltage value under different inrush currents, which has important reference value for designing efficient protection solutions.
Finally, the capacitance C0 and leakage current Il of the varistor are discussed. Capacitance C0 represents the capacitance value between the two electrodes of the varistor. This parameter has an important impact on evaluating the response speed and frequency characteristics of the varistor. The leakage current Il, that is, the current flowing through the varistor under the application of a specific DC voltage, is an important indicator to measure the stability of the varistor. Especially the change rate of leakage current after an impact test or under high temperature conditions. The stability of this change rate is a key factor in judging the reliability of the varistor.
Through in-depth analysis of the characteristic parameters of varistor and its performance in derating, we can not only better understand the working principle of varistor, but also be able to select and use varistor more effectively in practical applications. , thereby providing more reliable protection for electronic equipment. When designing a circuit protection scheme, these parameters should be considered comprehensively to ensure that protection requirements are met without affecting the normal operation of the circuit.