Radiators for solid-state relays manufactured by FAP

Solid–state relays (TTR) have many advantages, however, like all electronic devices, they have one very noticeable drawback - heat generation during operation. At first glance, this should not create problems during operation. But any device has an operating temperature limit, exceeding which can shorten its service life, or, in extreme cases, completely disable it. In most cases, it is sufficient to equip the device with a thermal switch that turns off the device in case of overheating.

However, for a solid-state relay, simply disconnecting when the temperature is exceeded is not enough. TTR is a semiconductor device, the permissible current of which directly depends on the temperature. The higher the temperature of the TTR, the less load it is able to control.

Dependence of the relay load current on the ambient temperature

It should be borne in mind that the permissible value of the load current indicated on the TTR body, as well as indicated in the documentation for it, is valid at a relay heating temperature of no more than 40°C (this is true for TTR of any manufacturer). When the temperature of the TTR exceeds 40°C, the permissible value of the load current decreases. For example, when the relay is heated to a temperature of 70°C, the permissible load current will decrease by 50%. Practice shows that a load with a consumption current of 5A is already capable of heating the relay above 40°C. Therefore, in order to comply with the operating conditions of the TTR, it is extremely important to take measures to limit their heating. And the most effective way to remove heat from the TTR is the use of cooling radiators.

The cooling radiators produced by the Obninsk plant "Aluminum Profile Factory" (FAP) are made of aluminum alloy AD 31 or AW6060 according to GOST 22233-01, GOST 8617-81. The range of radiators may not seem wide enough:

But at the same time, it is necessary to keep in mind a number of features of the use of cooling radiators.

Firstly, there is no unambiguous correspondence between the load current and the type of radiator required. The recommendations given in the documentation meet standard operating conditions (ambient temperature 25°C, air circulation, etc.). Accordingly, the radiator must be selected with some current margin, or (or simultaneously) increase its efficiency by additionally installing an air fan.

In addition, to ensure effective heat dissipation, it is necessary to install the TTR on the radiator using a heat-conducting paste. When installing cooling radiators inside the equipment or the mounting cabinet, care must be taken to ensure that nothing interferes with the natural air circulation through the cooling radiator. The radiator should always be positioned so that the air circulation flows (natural or forced) pass along the radiator cooling fins. Otherwise, the efficiency of the radiator will decrease significantly.

Based on the above, it can be concluded that RTR radiators with a discreteness of an acceptable current of 20A can be used to solve almost any tasks.