The difference in the selection of overvoltage / overcurrent between AC and DC input terminals?

Power Circuit Protection
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Question: Are there significant differences in the selection of overvoltage and overcurrent protection components between AC input terminals and DC input terminals?

Answer: There are differences. The higher the AC or DC voltage, the greater the differences.

Regarding the differences in the selection of overvoltage and overcurrent protection devices for the input terminals of AC (alternating current) and DC (direct current) power supplies.

The protection devices involved here include Fuses Fuses， Varistors, MOVs Circuit Breakers and various other circuit protection components.

  • There are indeed differences in the selection of overvoltage and overcurrent protection devices between AC and DC. And these differences become more significant as the AC or DC voltage increases.

  • For example, in high-voltage situations, AC voltage changes periodically, and its peak voltage
    The formula for calculating peak voltage for an AC voltage value from an RMS value
    This affects the selection of overvoltage protection devices. For MOVs in AC circuits, it is necessary to consider the peak voltage the MOV can withstand and its response characteristics within the AC cycle. In DC circuits, the focus is mainly on its DC voltage withstand value.

  • For overcurrent protection, since AC current also changes periodically, it will generate reactance effects in inductors, capacitors, and other components. Taking fuses as an example, the relationship between the effective value and the peak value of AC current affects the fusing characteristics of fuses. In DC circuits, the current is relatively stable, and the main consideration is the impact of the DC current magnitude on the fuse. In high-voltage AC and DC circuits, the differences in these characteristics are more obvious, resulting in greater differences in device selection.

More Littelfuse circuit protection products

Littelfuse Circuit Protection products provide stable and reliable signal transmission guarantee for all kinds of precision electronic devices by virtue of their precise adjustment relationship with capacitance, dynamic resistance, etc. in terms of high-frequency characteristics, and their performance is excellent in the industry.

More Q&A on Littelfuse Circuit Protection Products Technology:

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II. Questions Related to Selection

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  3. The difference in the selection of overvoltage / overcurrent between AC and DC input terminals?

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III. Questions Related to Applications

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