tomp wrote:
Could be but still a better choice than all your stuff blowing up. If you want something that can be used over again you probably want something that uses MOVs for fast response plus an electronic crowbar circuit in parallel. The MOVs will break down faster but before the average power dissipation gets too high to fry the MOVs the crowbar will trip shorting out the MOVs and the line. That can be a Triac, two back to back SCRs, or one SCR inside a bridge. Remember that because the device will present a short across the line once triggered you need to have the appropriate fuse/breaker in series to interrupt the current. The I2T rating of the device must be higher than the I2T pass through rating of the fuse or breaker or else the device will also be destroyed.
Whatever device you use, the trigger circuit for the device must be able to supply a large amount of gate current very quickly to make sure the trigger current gets across the whole die quickly or else there is a real chance that the area around the gate connection will melt from all the current going through that limited area. Also you should pick a device that has a high di/dt rating which is an indicator of how fast the whole die will turn on.
I have build devices like that to protect some circuits in remote locations subject to lightning surges that used fuses as the ultimate protection device. The crowbars worked successfully as indicated by the blown fuses but no blown circuitry. Forget trying to protect anything from a direct lightening hit. Hundreds of millions of volts coupled with thousands of amps will turn anything to gases and flying parts. However, most surges are caused by induced voltages and currents from nearby hits much like induced voltages from transformer primaries to secondaries work.
To add insult to injury -- Mr. Lightning marches to the tune of his own drum. Not only can he sneak in through power feeds, but also telephone lines, and in the case of large properties with walkway and roadway lighting, Mr. Lightning uses that path as well. Luckily I've never had anything fried either here or at my old house even when a strike took down a tree in my back yard that trashed the 13-kV overhead lines and the associated pole-mounted transformer. That doesn't mean it can't happen. A friend in upstate New York lost a bunch of stuff that was mainly his refrigerator, HVAC, TV, and his phono stage. To add insult to injury -- in the process 300-feet of 120/240-volt lines to his house was cooked and it was his nickel $$$. I should do more for myself but at least my video set-up is protected by a Tripplite AC conditioner and surge protector.
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