The ZnO varistor has a relatively small single-piece flow capacity, which is directly related to its own size. The manufacturing process of ZnO varistors is relatively complex, and the uniformity of the internal structure is poor, making it difficult to produce larger sized ZnO varistors (MOVs). For power system over-voltage protection Class B and Class C Surge Protectors (SPDs), the flow capacity should generally be in the range of 10 kA to 100 kA (impinging current waveform is 8/20 μS). To meet this requirement, Two MOV parallel methods are usually used.
At present, the use of two parameters of limiting voltage and dynamic resistance is mainly used for chip selection, but these two parameters are not easy to measure, and the dynamic resistance value changes with the inrush current. Therefore, it is particularly important to study an electrical parameter that measures the characteristics of parallel MOVs. important.
When we choose, we must use ZnO varistors with the same electrical properties to prevent damage to the circuit or capacitor due to performance conflicts.
Properties of ZnO Varistors: ZnO varistors (MOVs) are voltage limiting devices. When there is no surge, the MOV is in the low current density area, its resistance can reach more than 100MΩ, which is similar to the insulator. When there is surge, the MOV is in the saturation area, the resistance area drops sharply and can be reduced to Ω or even mΩ Grade, with the role of leakage amplification current, clamping high voltage. Therefore, ZnO varistors are widely used in surge protectors (SPDs).
Multiple MOVs in Parallel From the perspective of protection reliability, using multiple varistors in parallel is much more reliable than using only a single varistor. Because if a single varistor is used for protection, once the varistor is damaged, the protected device will lose protection; and when multiple varistors are used in parallel protection, if one of the varistors is damaged, the other can still be good. Take up protection tasks.
At present, the use of two parameters of limiting voltage and dynamic resistance is mainly used for chip selection, but these two parameters are not easy to measure, and the dynamic resistance value changes with the inrush current. Therefore, it is particularly important to study an electrical parameter that measures the characteristics of parallel MOVs. important.
When we choose, we must use ZnO varistors with the same electrical properties to prevent damage to the circuit or capacitor due to performance conflicts.
Properties of ZnO Varistors: ZnO varistors (MOVs) are voltage limiting devices. When there is no surge, the MOV is in the low current density area, its resistance can reach more than 100MΩ, which is similar to the insulator. When there is surge, the MOV is in the saturation area, the resistance area drops sharply and can be reduced to Ω or even mΩ Grade, with the role of leakage amplification current, clamping high voltage. Therefore, ZnO varistors are widely used in surge protectors (SPDs).
Multiple MOVs in Parallel From the perspective of protection reliability, using multiple varistors in parallel is much more reliable than using only a single varistor. Because if a single varistor is used for protection, once the varistor is damaged, the protected device will lose protection; and when multiple varistors are used in parallel protection, if one of the varistors is damaged, the other can still be good. Take up protection tasks.
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