Solid state relays is not yet well known by industrial installers.
However, more and more industrial automation professionals are interested in static relays when they become aware of their great advantages in some specific applications regarding electromechanical relays and contactors.
First great advantage.
The solid state relay, is an electronic relay.
That is, it contains no moving parts in its construction, so it is insensitive to structural vibrations that occur in the cabinet or control panel where they are installed.
On the other hand, since the conduction and cutting of the passage of the current through the physical contact of metal parts that are separated or joined together, as in the case of electromechanical relays, switches and contactors, there is no possibility of physical wear by friction or wear by electrical erosion of the faces of the electrical contacts.
In the case of the solid state relay, its action is carried out by the permeability or physical impermeability to the flow of electrons through the circuit to which the load is connected, which controls the internal semiconductor element of the relay, either a Transistor, a Triac, etc. when the control voltage applied to it is activated or deactivated.
This absence of wear of physical parts means that in practice the expectations of durability and service time, as well as the number of electrical operations of the static relays, are unlimited.
Its useful life can be estimated in more than 100 million operations, under the conditions of use specified for our solid state relays compared to only 100,000 – 200,000 estimated operations for an electromechanical relay.
The installer must always know and follow the recommended form of installation in relation to maximum voltage and current and do not forget the use of rapid protection fuses placed in series with the load.
It should be installed on an appropriate heat sink for each application and model of relay, using thermal paste or dissipation pad in the interface of the solid state relays with the radiator or the panel.
Forced ventilation in electrical cabinet or even the solid-state relay’s own heatsink prolongs the service time when used with permanently connected load.
The enormous number of full-load connection and disconnection operations that can be made by the zero crossing solid state relay, make them especially interesting in the control of electrical resistances by means of PID controllers (Proportional, Integral, Derivative), installed in single-phase or three-phase industrial furnaces, heating of houses, heating of fluid tanks, heating of injection machines of thermoplastics, injection molds, extruders thermostable, rubbers and thermoplastics, greenhouses etc.
Second great advantage
The solid state relay does not sound when working.
This feature is very important in some applications for the control of electric heating for domestic or residential use, such as hospitals, schools, offices, etc. , is the total absence of “noise” when carrying out the connection and disconnection operations due to the lack of mobile closing contacts by means of strong springs, as happens with the contactors, being able to also handle load currents far superior to these, up to 300 amps.