I'm building a dual voltage p/supply using a 7812 and a 7824. Thought I'd see how they cope first with an output short circuit. I found while they recover immediately after the short is removed, their method of coping during the short leaves a lot to be desired IMO.
With the 7824 reg mounted on a 75mm x 25mm x 3mm (3" x 1" x 1/8th") al. heatsink, an output short causes a .8A current draw at the (27vdc) input of the reg, and within a minute the entire heatsink is incredibly hot, my guess is 120 deg C+. With the heatsinks mounted on metal studs to space them off the plastic enclosure, I'm worried that if a short occurs for hours (eg while I'm away from home) the studs would conduct the heat as well and possibly cause the enclosure to melt or even catch fire.
Is this how they are supposed to work or did I buy cheapo poorly designed regs?
With the 7824 reg mounted on a 75mm x 25mm x 3mm (3" x 1" x 1/8th") al. heatsink, an output short causes a .8A current draw at the (27vdc) input of the reg, and within a minute the entire heatsink is incredibly hot, my guess is 120 deg C+. With the heatsinks mounted on metal studs to space them off the plastic enclosure, I'm worried that if a short occurs for hours (eg while I'm away from home) the studs would conduct the heat as well and possibly cause the enclosure to melt or even catch fire.
Is this how they are supposed to work or did I buy cheapo poorly designed regs?