Why do power plants use MOV's?

MOVS’s are a sacrificial component thus shortening the life of the unit. Can’t they use diodes or something like some other companies do?

I don’t see any in my P3.
Also why do you think they shorten the life of the unit? They take the hit while actually saving the rest of the unit!

After so many hits or one big one unit needs repair. Or it no longer has protection. According to PS tech support they all use MOV’s.

Actually that’s not entirely true. Using the appropriate MOVs and under most circumstances MOVs are not sacrificial. In fact, over all the years we’ve been building power equipment I think we’ve managed to lose perhaps fewer than 3 or 4 MOVs on the thousands
of units still performing well.

MOVs can be sacrificial, but again, that’s really rare and typically when not implemented correctly.

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As I understand it, MOVs work by shunting high voltage away from sensitive circuitry. They exhibit significant resistance until exposed to high voltage. When subjected to high voltage, they offer a low resistance path for this voltage to escape. For example, in a cheap power strip an MOV will shunt high voltage on the hot conductor to the neutral conductor, protecting the attached equipment.

I actually would’ve liked if PSA used these or shunting capacitors on relays controlling outputs. At least on P3, these relays simply break the inductive (transformer downstream) circuit, potentially shortening the life of these relays and also creating an audible pop through speakers.

You got it right. They are like zener diodes: they don’t do anything until they hit a certain predetermined voltage level and then they clamp down or conduct and the surge is shunted.

One of the many reasons I find the harnessing of electricity akin to magic.

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I actually found out there are the “men” and “boy’s” of MOV’s. I assume PS Audio uses the “men” versions. Much more robust. Still sacrificial but probably not in a lifetime unless perhaps direct lightening strike. Although you will have a lot more to worry about if that should occur. Hopefully not.