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High-power Wirewound Resistors Using Cooling Method to Dissipate Heat

Writer:Microhm Page View:Date:2019-04-22
A resistor is an electronic component that generates heat. When using a resistor, it needs to be designed for heat dissipation. If the resistor is not designed well, it can easily cause the resistor to be broken down or the entire resistor to be damaged. Especially for high-power wirewound resistors, such resistors generate a lot of heat during operation due to their high power. At present, air-cooling uses aluminum radiators, heat pipe radiators, circulating water and more to dissipate heat from high-power winding resistors.

High-power winding resistors use circulating water cooling to greatly improve heat dissipation efficiency, allowing the chip to operate at lower temperatures and increasing the life of high-power wirewound resistors. However, the use of circulating water cooling requires water circulation and processing equipment. In order to prevent rust and freezing caused by pure water, a mixture of water and alcohol is generally used. The mixing ratio affects the thermal resistance of the coolant. When the mixing ratio is 50%, the thermal resistance generally increases by 50%. Under normal circumstances, the water flow rate should be no less than 8 liters/min. In a hot and humid environment, the relative humidity in the air is relatively high. When the water temperature is low and the temperature of the surface of the water-cooled radiator is lower than the dew point, the surface will condense and affect the insulation. Measures should be taken according to the standard requirements to properly raise the water temperature and reduce the relative humidity of the ambient air.
When the high-power winding resistance is forced air cooling, the manufacturing process of the heat sink is different, and the thermal conductivity of the heat sink is much larger than that of the aluminum alloy heat sink. The thickness of the base plate of the radiator should meet the heat conduction. Especially for equipment that uses surge current, such as soft starter, the thickness of the bottom plate should be more than 20mm. The number of fins and the corrugation should take into account the fluid resistance under the premise of ensuring the maximum heat dissipation area, and the ratio between the height and the thickness of the fins should be reasonable.

High-power wirewound resistors should be installed in place when installing the heat sink. The layout of the device on the heat sink should be such that the thermal resistance at the center of the heat sink is minimal. When installing the heat sink surface of the module, paying attention to flatness and surface roughness. If the surface is recessed, it will directly lead to an increase in contact thermal resistance.In order to make the contact thermal resistance small, a very thin layer of thermal grease should be evenly applied between the heat sink and the mounting surface of the high-power winding resistor.
Generally, the above three points can be used to dissipate heat from high-power wirewound resistors. However, the environment of high-power wirewound resistors will change. The heat dissipation method of each type of it will also be different. It is necessary to select the high-power winding resistance heat dissipation method in the environment, so that it can accurately judge which high-power winding resistance heat dissipation method is adopted.


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