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Query regarding (tidu231) 30-W Ultra-Wide Range Power Supply for Protection Relay

Manish Sharma2
Intellectual 380 points

Dear Sir,

 

I was checking the power supply for protection relay tidu231 “30-W Ultra-Wide Range Power Supply for Protection Relay”.

Surge rating as mentioned in the document:

  1. 2 kV Differential Mode
  2. 4 kV Common Mode

 

while going through the document, before MOV a fuse is used.  With the fuse we are able to meet the surge requirement? Also is fuse is recommended for such application?

  • 0
    TI__Mastermind 40300 points

    Hello Mannish,

    Thank you for your interest in the TIDU231 Reference Design. 

    This fuse, like fuses in most other power supplies, is used for last-resort protection against a pcb fire due to some catastrophic fault on the board.  It should open only in the case of sustained excess input current, to prevent uncontrolled heat which could start a fire.

    In electronic equipment like this, the fuse is generally not user-replaceable because whatever led to the excess current to blow the fuse has also resulted in non-user-repairable component or circuit damage.  A such, the fuse rating is chosen to provide the appropriate level of protection for the normal power level while withstanding brief overcurrents due to surges and other line transients.  The fuse itself is not involved with surge protection, but must accommodate the current peaks associated with such surges.  

    For the TIDU231, the fuse is a 5-A time-delay (slow-blow) fuse soldered to the board with radial leads.  The time delay characteristics allow it to stay intact during line surges and turn-on inrush, but open on sustained current > 5Arms.  Time-delay fuses are not intended and not expected to protect any semiconductor or other component from overloads.  They are expected to protect the board and assembly from igniting a fire.  Fuse vendors have complete information on how to select the proper fuse for an application.

    Regards,
    Ulrich