James Sweet wrote in
:



Fair enough. But how about apples for apples? the transzorbs in your
link are rated at only 500W. Sure the common MOVs degrade when hit with
their rated 100 kW or so, but if you hit them with only 500 W (like the
transzorbs) they will last virtually forever. The physical volume of
active material is simply vastly larger in a MOV than in a transzorb.
Transzorbs are great if used within their ratings, but MOVs can have
vastly higher ratings, and can also provide good lifetime when de-rated
in lower energy circuits, so they shouldn't be dismissed without proper
consideration.

Cheers, Tony



They're really aimed at different applications. MOVs are for absorbing
very large but infrequent transients, and are normally used to protect
the input side of a power supply or other device connected to an
external power or signal source. TransZorbs are for absorbing small
frequent spikes, as you'd get from switching inductive loads.

An interesting tangent, a transzorb wired to trigger a triac is a far
more robust replacement for the SIDAC used in a lot of HID lamp
igniters.


I think I read that varistors were also good for very high speed response to
ESD, adequate for laser diode protection. Robin Bowden showed me that a zener
and an RC filter could be just as good or better in most contexts of diode
drivers but I found a LOT of cheap varistors on eBay and they are impressive
when tested with gas ignitors. There's a nice page comparing the merits of
ceramic caps, zeners, transorbs and varistors, but I'm too tired to prompt
Google to hand it to me this morning. Either that or Google's SNR is
declining further.