What is the difference between « Thyristor rating » and « Switching current » ?

This question comes up frequently and we are pleased to answer it in this dedicated article.

Thyristors are used as the switching components in solid state relays for alternating currents. The ratings of our power components are specified in our technical data-sheets as well as in our selection guide catalogue. These products must be mounted on heatsinks in order to reach nominal performances. “Thyristor rating”, which is an indication of the size of the power component, must not be confused with “Switchable current” which depends on how the relay or contactor has been built and how it is used. To correlate the switchable current with the relay and your application, refer to the tables and thermal curves in our data sheets for products that are not equipped with heatsinks as standard.

Here is an example with a single phase Solid State Relay SO965460 having a 60A thyristor rating.


Thyristor rating SO965460

On our e-catalogue website we are also mentioning the Thyristor Rating value for SSRs which are not coming mounted on heatsink.


SSR capacity @ 40°C ambiant temperature are as following:

Thermal curve for SO965460

Should you have any question, feel free to contact our Technical Experts.