Hi TechForum/DigiKey, On the weekends, I do repairs of the small electronics in my home among other tasks. During the week, I have a degree in physics and do scientific research at the local university. So, I have some background with this sort of work, but it is not my primary focus. I am current…

Don’t have time this long weekend to read this in detail (I’m in MA so it’s Patriots’ Day weekend). However this tip may prove helpful. Varistors almost always serve a single purpose, to clamp large voltage spikes to a safe level. It is virtually always safe to simply remove the varistor from the …

Thank you for taking the time to respond during your long weekend. So, it sounds like the varistor acts almost like a secondary fuse. As long as I’m not anticipating there being any voltage spikes in my system. This should be okay for testing if the rest of the circuit is okay? My main questions i…

Hello, Welcome to the DigiKey tech forum. The fuse you selected, Digikey part 4598-MST6.3A250VCT-ND looks to be a good match. The varistor , DigiKey part 118-MOV-14D511K-ND also looks to be a good match, the markings usually break down as 14 (diameter in mm) , 511 (varistor voltage 51 with 1 as t…

Hello Allison, We do not carry the 14N511K part, so I searched for a datasheet on-line. The one I found said the N was for Different Internal Structure. When I checked the 14D511K part, it said the 14D was for the 14mm Diameter. Maybe someone else can add to this, that knows a lot more about the…

Hi Allison, Welcome to DigiKey tech forum. I found a couple data sheets online that seem to somewhat depict what that N calls out. cov_14n511k_Lcs01_link.pdf 1685.52 KB and [image] 14N511K PDF Part #: 14N511K. Description: Metal Oxide Varistors …

Thank you all for the information. I’ve found it edifying. It sounds like the D has a different material composition. However, it shouldn’t be a problem if it has the same voltage characteristics. If the technique is newer, maybe it was to address the problem which resulted in the Ns failure. I wi…

[image] Allison: So, it sounds like the varistor acts almost like a secondary fuse. As long as I’m not anticipating there being any voltage spikes in my system. This should be okay for testing if the rest of the circuit is okay? I believe you got the gist of it. However a varitor is almost n…

Oh, that makes sense. Thank you for that insight. I’m interested in learning everything I can about well everything I can. I love this sort of stuff. So, when the varistor has not been tripped, it has a high resistance and not much current flows through that pathway. However, when it encounters a r…

[image] Allison: it triggers and creates a short circuit that Close, but not quite. It doesn’t create a true short circuit, but rather it tries to limit the voltage by shunting much of the current to ground during a surge. The voltage across the device during a voltage surge event will stil…

Once a varistor fails it will be very close to a dead short and that condition is non-reversible. So in high power circuits you must have other protection in the circuit to prevent the failed varistor from catching fire. The other protection is usually a fuse or circuit breaker between the varisto…

Part Identification: Fuse and Varistor from a PSU

Power Circuit Protection

Ryan_2724 April 17, 2024, 10:51pm 13

Hi @Allison You may enjoy reading Metal Oxide Varistor (MOV) Specifications & Selection Guide

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Part Identification: Fuse and Varistor from a PSU

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