Re: The 2013 El-cheapo Power Supply Roundup
Posted: January 28th, 2014, 1:47 am
Wester: I didn't test the rectifiers. The PSU just works fine after replacing them, so I think it's a pretty safe assumption that one of them was the culprit.
LongRunner: Possibly I figured that, While the heat may certainly reduce the current output, it's important to remember that those things are rated for 30A at 155°C. To have them fail that far below the combined 60A, the temperature would have to have exceeded the TJMax rating of 175°C. Even once we factor in the thermal resistance*, we would still end up at over 160°C at the casing. If things had really been getting that hot, there would have been far more damage to the plastic which was glued to them, as well as to the insulation washers than what I saw.
*The rated voltage drop at 30A load at high temperatures is 0.8V, so 0.8V x 20.15A Load (which each rectifier would have been under), which equates to 16.12W dissipated per rectifier. The rated thermal resistance is 0.9°C/W, which gives us a 14.508°C Delta, and 175 - 14.508 = 160.492
LongRunner: Possibly I figured that, While the heat may certainly reduce the current output, it's important to remember that those things are rated for 30A at 155°C. To have them fail that far below the combined 60A, the temperature would have to have exceeded the TJMax rating of 175°C. Even once we factor in the thermal resistance*, we would still end up at over 160°C at the casing. If things had really been getting that hot, there would have been far more damage to the plastic which was glued to them, as well as to the insulation washers than what I saw.
*The rated voltage drop at 30A load at high temperatures is 0.8V, so 0.8V x 20.15A Load (which each rectifier would have been under), which equates to 16.12W dissipated per rectifier. The rated thermal resistance is 0.9°C/W, which gives us a 14.508°C Delta, and 175 - 14.508 = 160.492