Well the SPD part on its own seems to retail at about half that.
Inside the wylex and crabtree units are pretty much both like this teardown video by efixx .
I found the spring - loaded solder joint to disconnect and operate the warning flag and micro switch something of a throwback to a bygone era, that reminded me of the old tellys I used to sometimes repair as a teenager and in my early 20s.
In the screenshot below you can see how the L-E is a just a varistor (semiconductor transorb), the blue thing, and NE is the gas filled ceramic cylinder with metal caps at both ends - a sort of enclosed 'spark gap' of more controlled behaviour if you will.
regards Mike
edit PS
For those few of us who like to design the same level of protection into our own equipment and enclosures one can get similar transorb varistor parts offering the same functionality, including the warning microswitch output built in like these with solder tags for about 15 -20 quid in modest quantities (falling to about half that in bulk).
Quite a bit less if you do not want the warning output.
Non rupturing up to 200kA apparently. Part of me would like to see that spec tested, but as it is a limit many substation fuses might not meet anyway, this is not one to trouble the scorers.
The high current gas discharge tubes are quite a bit cheaper ( examples ), at 1/3 to 1/2 the price of the varistor parts depending on model chosen.
Well the SPD part on its own seems to retail at about half that.
Inside the wylex and crabtree units are pretty much both like this teardown video by efixx .
I found the spring - loaded solder joint to disconnect and operate the warning flag and micro switch something of a throwback to a bygone era, that reminded me of the old tellys I used to sometimes repair as a teenager and in my early 20s.
In the screenshot below you can see how the L-E is a just a varistor (semiconductor transorb), the blue thing, and NE is the gas filled ceramic cylinder with metal caps at both ends - a sort of enclosed 'spark gap' of more controlled behaviour if you will.
regards Mike
edit PS
For those few of us who like to design the same level of protection into our own equipment and enclosures one can get similar transorb varistor parts offering the same functionality, including the warning microswitch output built in like these with solder tags for about 15 -20 quid in modest quantities (falling to about half that in bulk).
Quite a bit less if you do not want the warning output.
Non rupturing up to 200kA apparently. Part of me would like to see that spec tested, but as it is a limit many substation fuses might not meet anyway, this is not one to trouble the scorers.
The high current gas discharge tubes are quite a bit cheaper ( examples ), at 1/3 to 1/2 the price of the varistor parts depending on model chosen.
