I am using Solid state relays to On/Off heaters so as to control temperature. In case if heaters get short,immediately the Solid state relays ( SSR ) also gets short and I need to change new one.Even though I have Fuse protection the SSR and Fuse gets blown. Since the Cost of SSR is high,I have so many troubles.
So any one Please suggest some ideas to prevent SSR failure.Is there any protection like Varistors , RC circuit to prevent this
You answered your own question The SSRs are broken when the heater is a short.
Fix the problem with the heaters !
A super fast fuse combined with derating of the SSRs may help too.
Graham
yes, SSR's can short if the load they are driving shorts how ever, in cases like we have at work we have line fuses that are rated much lower than what the SSR is and thus you would think they shouldn't short but they do at times. the problem we had at work was not so much the load but the inductive energy and unbalanced load effects that multiply the voltage above the limits of the SSR.. that is most likely your problem. we solved our problem by running the lines to the heaters spaced apart from other lines and used a TVS on each SSR brick. now if there is a loose connection or short, only the fuse blows if needed.
"Jamie"
** If an SCR or Triac is overvoltaged by a spike or similar (in the off state) then it simply triggers on for the rest of the cycle. This is not destructive to the device.So it is not destructive to SSRs either.
......... Phil
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