Dear Sir/ Madam
Good Evening!
We have our ace product, the Annunciator which can be operated from 85 to 270V AC.
We have designed SMPS Power supply which operates from 85 to 270V AC.
We want to design over voltage protection circuit at Mains supply side so that when voltage is within 85 to 270V AC then product shall function as per specification but if supply voltage exceeds 300V AC then the product (Annunciator) shall be protected from it.
We tried Resettable fuze and MOV combination but MOV is blasting.
Please help and guide us to resolve.
Regards,
EAPL R&D Team.

 

See the idea:

 

Dear Sir/ Madam
Good Evening!
We have our ace product, the Annunciator which can be operated from 85 to 270V AC.
We have designed SMPS Power supply which operates from 85 to 270V AC.
We want to design over voltage protection circuit at Mains supply side so that when voltage is within 85 to 270V AC then product shall function as per specification but if supply voltage exceeds 300V AC then the product (Annunciator) shall be protected from it.
We tried Resettable fuze and MOV combination but MOV is blasting.
Please help and guide us to resolve.
Regards,
EAPL R&D Team.

You can get MOVs so big you have to fix them to a wall - probably not cheap though.

 

If its a common problem and low voltage dips for excessive periods are not a common problem you may want simply use a small auto-transformer to buck the ~270 VAC line down a ways.

If that's not a workable solution then it may be better to over build the HV side to work safely at far higher input voltages but keep the stock input ratings the same. I've seen that design cheat many times in higher quality power supplies and like devices. 85 - 265VAC ratings but can safely and reliably work at <60 - >320 VAC inputs if they have to.

It's that or add a replaceable fuse and a MOV behind it that's large enough to blow it countless times without giving up itself that way if the customer keeps blowing the fuses due to overvoltage that's their problem to deal with and fix and not yours. Put responsibility for power quality control where it belongs.