Grenerally thyristor swiches are maintenances-free. But nevertheless some points have to be repected :
a)Thyristor switches, equipped with fan,have to be checked for the correct fan function every 2 years, if a fan is defective ,it has to be replac
ed by the original part. Using another fan with less air flow can cause over overheating and this can destroy the thyristors.
b)Generally;the heat sink have to be cleaned regulary, because the cooling capacity can be reduced by pollution.
c)Pollution between the connections of the thyritors have also to be removed, because of this leakage distances are reduced. This can cause a voltage flashover.