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Mr 1936 · 29th Jan 2023, 9:04 am

Hi

There are two main approaches to power resistors. One is a metalclad type designed to be bolted to a heatsink so as to increase its surface area. The bigger the heatsink, the smaller the temperature will be above its surroundings. If you leave out the heatsink and just mount in free air, a 50 Watt type must be derated to 10 Watts and will run reasonably warm at that dissipation.

The other type is made of materials that can stand a high temperature e.g. ceramics. Smaller surface area but much higher surface temperature so must not be too close to anything that would be damaged by heat.

29th Jan 2023, 9:04 am	#64
Mr 1936 Heptode Join Date: Mar 2017 Location: Romsey, Hampshire, UK. Posts: 524	Re: What did I get myself into? Murphy A40C. Hi There are two main approaches to power resistors. One is a metalclad type designed to be bolted to a heatsink so as to increase its surface area. The bigger the heatsink, the smaller the temperature will be above its surroundings. If you leave out the heatsink and just mount in free air, a 50 Watt type must be derated to 10 Watts and will run reasonably warm at that dissipation. The other type is made of materials that can stand a high temperature e.g. ceramics. Smaller surface area but much higher surface temperature so must not be too close to anything that would be damaged by heat.