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Discussion Starter · #1 · (Edited)
Hi,
I have three questions regarding the surge protection of a circuit:

1) My understanding is that the fuse voltage rating needs to be more or equal the operating voltage of the AC circuit but I've seen 250VAC fuses used for universal input line voltage values.
How is that possible? Is it an exception?

2) When you use a fuse and a MOV on the AC input for surge protection. It is common practice that the fuse shouldn't melt when MOV is suppressing the voltage spike in the input. So what does that mean? I believe it means that the transient energy of the varistor needs to be less than the melting I2t of the fuse. Am I right?

3) What is the big difference between a fuse block and a simple fuse clip holder? How do designers choose between them?

Thanks
 

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universal voltages means 100-240v voltages from different countries so they can all use 250v fuses.
fuse should blow only when the mov is absorbing a big spike, if it doesnt blow the mov will explode or will fry pcb board
a fuse block is a complete part to hold the fuse, a fuse clip is just a small metal part thats hold the fuse
the fuse clip is a part of the fuse block
 
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