Method and Apparatus for Detection of a Fuse Failure

Abstract

A method for detection of a failure of a protective fuse used to protect an associated load against overcurrent and/or against overload, wherein the method includes the steps of: measuring an electrical current, flowing through the protective fuse to the load by means of a current sensor element, determining a thermal energy generated in the protective fuse depending on the measured electrical current, and automatically detecting a failure of the protective fuse if the determined thermal energy exceeds a predetermined threshold value and if the electrical current, measured by the current sensor element has stopped flowing through said protective fuse.

1 . A method for detection of a failure of a protective fuse used to protect an associated load against overcurrent and/or against overload, the method comprising the steps of:
 measuring an electrical current flowing through the protective fuse to said load by means of a current sensor element;   determining a thermal energy generated in the protective fuse depending on the measured electrical current; and   automatically detecting a failure of the protective fuse if the determined thermal energy exceeds a predetermined threshold value and if the electrical current measured by the current sensor element has stopped flowing through said protective fuse.   
     
     
         2 . The method according to  claim 1  wherein if the determined thermal energy has exceeded the predetermined threshold value and the electrical current measured by the current sensor element has stopped flowing through said protective fuse, a fuse failure detection signal indicating a likely failure of the protective fuse due to a short circuit current is automatically generated. 
     
     
         3 . The method according to  claim 1  wherein the thermal energy is calculated as an Ampere squared seconds value and compared with the predetermined threshold value. 
     
     
         4 . The method according to  claim 1  wherein a failure of the protective fuse is detected if as a further condition a received switching state signal indicates that the associated load has not been switched off externally by a protective switch. 
     
     
         5 . The method according to  claim 1  wherein if the determined thermal energy does not exceed the predetermined threshold value but the amplitude of the measured electrical current is higher than a predetermined rated current, an energy input into said protective fuse caused by a flowing electrical current is determined. 
     
     
         6 . The method according to  claim 5  wherein if the determined energy input into the protective fuse by the electrical current exceeds a predetermined threshold value, an overload failure warning signal indicating an imminent failure of the protective fuse due to an overload current is automatically generated. 
     
     
         7 . The method according to  claim 6  wherein the energy input into the protective fuse is determined by calculating a heat transfer balance for the protective fuse as a difference between heat generated by the electrical current flowing through the protective fuse and heat dissipated by the protective fuse. 
     
     
         8 . A fuse failure detection apparatus provided for detection of a failure of a protective fuse used to protect an associated load against overcurrent and/or against overload, said fuse failure detection apparatus comprising:
 a current sensor element adapted to measure an electrical current flowing through the protective fuse to said load;   a determination unit adapted to determine a thermal energy generated at the protective fuse depending on the electrical current measured by said current sensor element; and   a failure detection unit adapted to automatically detect a failure of the protective fuse if the determined thermal energy exceeds a predetermined threshold value and if the electrical current measured by said current sensor element has stopped flowing through said protective fuse.   
     
     
         9 . The fuse failure detection apparatus according to  claim 8  wherein the failure detection unit is adapted to automatically generate a fuse failure detection signal indicating a likely failure of the protective fuse due to a short circuit current if the determined thermal energy has exceeded the predetermined threshold value and if the electrical current measured by the current sensor element has stopped flowing through said protective fuse. 
     
     
         10 . The fuse failure detection apparatus according to  claim 8  wherein the determination unit is adapted to calculate an Ampere squared seconds value representing the thermal energy generated at the protective fuse in response to the electrical current measured by the current sensor element. 
     
     
         11 . The fuse failure detection apparatus according to  claim 10  wherein the failure detection unit is adapted to compare the calculated Ampere squared seconds value with a predetermined Ampere squared seconds value to generate the fuse failure detection signal, if the determined thermal energy has exceeded the predetermined threshold value and the electrical current measured by the current sensor element has stopped flowing through said protective fuse and if a received switching state signal indicates that the associated load has not been switched off externally by a protective switch. 
     
     
         12 . The fuse failure detection apparatus according to  claim 8  wherein the determination unit is further adapted to determine an energy input into said protective fuse caused by the flowing electrical current if the determined thermal energy does not exceed the predetermined threshold value but the amplitude of the measured electrical current is higher than a predetermined rated current. 
     
     
         13 . The fuse failure detection apparatus according to  claim 8  wherein the failure detection unit is adapted to generate an overload failure warning signal, if the determined energy input into the protective fuse by the electrical current exceeds a predetermined threshold value, wherein the generated overload failure warning signal indicates an imminent failure of the protective fuse due to an overload current. 
     
     
         14 . The fuse failure detection apparatus according to  claim 8  wherein the determination unit is adapted to determine the energy input into the protective fuse by calculating a heat transfer balance for the protective fuse as a difference between heat generated by the electrical current flowing through the protective fuse and heat dissipated by the protective fuse. 
     
     
         15 . The fuse failure detection apparatus according to  claim 8  wherein the current sensor component is adapted to measure an electrical DC current and/or an electrical AC current. 
     
     
         16 . The fuse failure detection apparatus according to  claim 8  wherein the current sensor element is serially connected to the protective fuse within a current supply path of the load or is attached to the current supply path of the load. 
     
     
         17 . The fuse failure detection apparatus according to  claim 8  wherein the failure detection unit comprises an interface to receive a switching state signal from a protective switch which is connected in series with the protective fuse along the current supply path of the load. 
     
     
         18 . An adapter device comprising a fuse failure detection apparatus provided for detection of a failure of a protective fuse used to protect an associated load against overcurrent and/or against overload, said fuse failure detection apparatus comprising:
 a current sensor element adapted to measure an electrical current flowing through the protective fuse to said load;   a determination unit adapted to determine a thermal energy generated at the protective fuse depending on the electrical current measured by said current sensor element; and   a failure detection unit adapted to automatically detect a failure of the protective fuse if the determined thermal energy exceeds a predetermined threshold value and if the electrical current measured by said current sensor element has stopped flowing through said protective fuse.