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Why install a radiator for solid state relays?
Why do solid-state relays and SCR modules need radiators? Since both of them use SCR as the main overcurrent device and SCR is a power device, there is a certain conduction voltage drop, that is, conduction resistance, in use. Therefore, heat is generated and cannot be distributed in time. SCR will be damaged quickly and cannot be recovered. Therefore, all the loads with a certain current should be equipped with radiator plates, and air cooling and water cooling should be added when necessary. The calorific value of the solid state relay or module is mainly related to the practical current of the driven load, but has little to do with its own current level.
Calculation formula of calorific value (two kinds): single-phase solid state relay, single-phase AC voltage regulator module, R series solid voltage regulator calorific value = practical load current (ampere) x1.5 watts/ampere, for three-phase solid state relay, three-phase AC voltage regulator module, the practical load current should be the sum of three-phase practical load current. Heat generation = practical load current (amperes) x 3.0 watts/amperes.
The function of the radiator is to distribute the heat generated by the solid-state relay or module. The heat dissipation effect is not only related to the size of the radiator, but also to the ambient temperature (season), ventilation conditions (natural cooling or forced cooling and air volume) and device density, etc. The elements are all related. Reference specification for heat dissipation: Make the temperature of the base plate (contact surface with the radiator) of the solid state relay or module not exceed 80°C. Therefore, in practical applications, a temperature switch (with a pair of normally closed contacts) of only 75°C can be arranged at the edge (within 20mm) of the radiator device surface near the solid state relay or module, and the control signal of the solid state relay or module can be connected to the pair of normally closed contacts. In this way, when the temperature of the detection point exceeds 75°C, the normally closed contacts jump open, cut off the control signal, and forcibly close the output of the solid state relay or module to maintain it. In the center of the common practice current exceeding 50A per phase, high device density and high ambient temperature, it is best to use temperature switch for maintenance.
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