AudioGeek said:
Try to get TO-3 device. That can handle more power, and accept higher temperature. Or try IRFP260N, which is rated to 300W at 25C. Mount them without insulator, and insulate the whole heatsink. And You have to use separated heatsink for each device! Fan cooling is good solution for it.
sajti
AudioGeek: OK, my suggestion is to use the IRFP250N, and mount it on a black anodized surface without insulator (but with thermal grease). It will withstand easily the 100 Watts of dissipation, if the heat sink stays below 70 C.
IRFP150N will also do nicely. but IRFP250N is the cheapest device.
IRFP150N will also do nicely. but IRFP250N is the cheapest device.
Lars Clausen
Easily!!!???
Well, if you are going to dissipate that much heat I would suggest polishing the contact surfaces so they are are smooth and shiny as you can make them, use as thin a layer of heatsink grease as you can make (it should be barely visible except at the edges to give a visual hint) and use a variac to feed it and measure the dissipation over time. If you did a good job, the heatsinks will get hotter faster. Having a heatsink measure 70 degrees celsius is not a guarantee that the device won't fail.
Easily!!!???
Well, if you are going to dissipate that much heat I would suggest polishing the contact surfaces so they are are smooth and shiny as you can make them, use as thin a layer of heatsink grease as you can make (it should be barely visible except at the edges to give a visual hint) and use a variac to feed it and measure the dissipation over time. If you did a good job, the heatsinks will get hotter faster. Having a heatsink measure 70 degrees celsius is not a guarantee that the device won't fail.
Upopa: You are absolutely right! However i was only discussing the safe dissipation, not safety regulation requirements.
yldouright: I agree, even if the IRFP250N may be within SOA limits, also at 100 Watts, why not take the biggest available device, at just a dollar extra cost. The IRFP260N will safely dissipate around 200 Watts at 80 C tc (what you get at 70 C heat sink temp, when mounting as proposed).
I have used a IRFP150 device as heater for years for testing heat sink values. Even with changing surfaces and loads up to 100 Watts, it has never failed.
yldouright: I agree, even if the IRFP250N may be within SOA limits, also at 100 Watts, why not take the biggest available device, at just a dollar extra cost. The IRFP260N will safely dissipate around 200 Watts at 80 C tc (what you get at 70 C heat sink temp, when mounting as proposed).
I have used a IRFP150 device as heater for years for testing heat sink values. Even with changing surfaces and loads up to 100 Watts, it has never failed.
Upupa Epops said:70 ° C at by finger touchable parts safety norm for home electronic not permit ( not permit temperature over 60 ° C). You must use larger heatsink
It's true, but if You put the heatsink inside the box, it can be hotter, and You can insulate it electrically from the box, and put the output device without any insulator. At 100W .2K/W insulator means 20 degree more temprature for the junction...
sajti
Lars Clausen said:
Hi Lars,
I had some problem with IRFP devices on high power levels. When I put the amplifier together it works properly for few days, but after I lost it... After some investigation I found, that the I lost the mounting force, due the large temperature changes. So finally I use some more fixing for it. I never had this problem with TO-3 devices, such as IRF150.
Another issue is the fan cooling. I avoided it for long time, because it noisy. Than I tried a 12V fan with 6V DC. It runs slowly, and no noise, but reduce the heatsink temperature with 15 degree
sajti
my cooling system have four fan in amp: http://akotov.narod.ru/2.html. Power dissipation ~230watt.
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