> [EMAIL PROTECTED] wrote: > Unfortunately, I got a reply from Samlex saying the OVP is > of a feedback type, not a crowbar, which explains Jeff's experience > with the SEC-1212.
Not so good... > A long time ago I happened to find a crowbar "bar" made by Lambda > at the local TRW swap meet. I added it to a supply without built-in > OVP to add said protection to the equipment. I have seen a number of small crow-bar pc daughter boards tacked onto various "Power One" (a brand name) type power supplies. They are easily copied or even lifted off the original supply for use in other locations. > I wonder if similar devices are commonly available somewhere? They are but nothing comes to mind right away... You might check with Kitsrus, Jameco, Electronics Rainbow, Marlin P. Jones and a few other kit mfgr/retailers to see what they offer. If not I can and would share some of my notes if you want to "roll your own". > That & a fuse on the output of an SEC-1223 & I think > I'd feel comfy using it at one of my sites. > Bob NO6B The key points are location, function & size. Where will the crowbar be placed? What will the crowbar do to everything on the dc bus at a fault condition? What happens after the fault condition goes away and or remains? Does the crow-bar device/circuit have a large enough capacity. Astron designed their crowbar circuit to short the supply output. The shorted output protects the user equipment and tries to force the AC Mains fuse to open through excessive transformer primary current draw. The bad news is found when modest size power supply - ac mains fuses are replaced with excessive large current values (the trusty 25 or 30 amp 3ag fuse everyone seems to have a lot of...). Not enough current draw through the faulted secondary side of the supply to open the wrong size installed ac mains fuse. Somethings got to give... and it's often very hot when it does. cheers, s.
