Re: MOVs as an SG

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Charles Hobson by way of Terry Fritz <twftesla-at-qwest-dot-net>" <charles.a.hobson-at-btinternet-dot-com>


----- Original Message -----
From: Tesla list <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Friday, July 20, 2001 11:49 PM
Subject: Re: MOVs as an SG


> Original poster: "Terry Fritz" <twftesla-at-qwest-dot-net>
>
> Hi Jason,
>
> It doesn't work.  The MOVs may conduct when the voltage reaches say 20001
> volts but they will stop conducting when the voltage reaches 19999 volts.
> Normal spark gaps start conducting at say 20001 volts and "stay
conducting"
> until the current drops to zero.  So spark gaps stay shorted throughout
the
> firing cycle where MOVs will stop conducting far too soon.

snip

Is this MOV  behavior the same as that of two Zener diodes connected back to
back? I am also curious about the failure mode of the MOV. Do they fuse and
become shorted, or do they blow apart and become open circuited when
subjected to excessive currents due to voltage spikes? It appears that  they
would fail every time in a pig type transformer secondary circuit when over
voltage is experienced.

Chuck