Should the fuse be placed before or after pressure sensitive?
User questions are as follows:
At the same time the use of fuses and varistors, I generally believe that the first fuse, and then the varistor.
This consideration is the varistor work, through the burning fuse, the power to the broken system.
But it is often seen that the varistor is used before the fuse
I guess they design this reason is that the pressure sensitive is only to prevent lightning and so on, so that the lightning is over, the fuse is good, can work properly.
Yesterday, I had a chat with two suppliers, one is AVX, one is sunlord
I asked the question, but the answer was different,
AVX said that before the pressure sensitive fuse, sunlord said that the fuse after pressure sensitive.

As above, this is the fuse in the varistor before, when there is a high voltage (such as lightning) from Vin came in, you see what happens, should be the varistor damage, also broken fuse. Analysis of the reasons: Vin has a high voltage, the varistor RV7 short circuit, then the current through the fuse directly to the ground short circuit, will produce a large current. Absolute broken fuse. Therefore, the fuse with the varistor is broken at the same time
The following look at the fuse after the pressure sensitive resistor, as shown below

This is to be divided into two kinds of situations
The first case is that the Vin has a high voltage (such as lightning) to come in, at this time the varistor RV8 short circuit, fuse F3 there is no large current through, so the fuse will not break. Behind the circuit will not be damaged, this time the varistor is damaged, the fuse intact.
The second case is the Vin power grid transient fluctuations in the large current, but the voltage is not changed. At this point the varistor RV8 is not damaged, as usual work. However, because of the high current F3 fuse, fuse immediately fuse. The following circuit is protected. At this point, the varistor is fine, the fuse is broken.
The above analysis is very detailed, you think about the fuse should be placed in front or behind it. Also some people do not know, please contact our website online technical customer service.