Manufacturers of fuses and their customers often encounter a frustrating issue—abnormal fuse fusing during the assembly and production of complete machines. This means that during certain powered tests or inspections in the production process of the customer's product, an occasional proportion of fuses are found to be burnt out. When another fuse is replaced, everything returns to normal. Does this indicate poor quality consistency among the fuses in this batch? Can the use of these fuses guarantee the startup quality of this batch of complete machines? Will the replaced fuses withstand the surge currents from multiple on/off cycles during actual use? How should we consider and handle this situation?
Fuses, as sensitive to current components, are designed to judge overcurrent conditions: melting when excessive fault currents flow is the protective function they should perform; for non-fault overcurrents like transient pulses, fuses should withstand a sufficient number of occurrences to ensure the normal operation of the entire unit. The currents during the above tests or inspections generally do not exceed the startup pulse during normal operation, and the number of power-on cycles does not exceed 10. The fuse should not operate under these conditions. If an abnormal melting occurs, it is definitely indicative of a problem. Simply replacing the fuse or increasing its capacity is not reassuring if the cause of the abnormal melting is not promptly identified.
We first need to inspect the actual operation of the process that encountered issues: for manual operations, we must rule out the possibility of a short circuit during the process; for machine operations, we must check if the actual output current exceeds the fuse's tolerance limit; some issues can be resolved during the process analysis. After confirming that the operation process is issue-free, we can proceed with further in-depth analysis.
We must consider both overcurrent and fuse aspects separately and simultaneously.
1. Whole machine customers need to inspect the size of the whole machine circuit pulse current and check for any anomalies. When analyzing issues, consider two factors: first, whether there were errors in the selection calculation at the time, such as not capturing the pulse waveform due to the randomness of the startup pulse, not considering the distribution range of the fuse melting thermal energy value during calculation, or not accounting for sufficient aging margin for multiple impacts, all of which could lead to deficiencies in the selection process; second, whether there have been changes in the circuit condition during production, such as changes in circuit structure due to changes in machine types, modifications in specifications or brands of certain components in the circuit, or parameter changes in capacitors, inductors, and switches, etc., all of which could cause changes in the circuit pulse waveform. The application engineer from the fuse manufacturing factory needs to cooperate with the customer for circuit technical analysis and measurement of the actual pulse energy, systematically eliminating each change, and both parties together analyze and assess the situation.
2. The fuse manufacturing factory needs to inspect and test the size of the melting thermal energy value of the fuses for any abnormalities. When analyzing issues, consideration should be given from two perspectives: Firstly, the melting thermal energy value of this batch of fuses meets the product specification requirements; however, the distribution of product parameters between batches may cause the melting thermal energy value of this batch to be smaller, creating a significant gap compared to other batches used in trial production or previous production. Secondly, the melting thermal energy value of this batch of fuses has exceeded the product specification requirements, or the large dispersion between product units may lead to some products having a melting thermal energy value below the specification range. In addition to the fuse manufacturing factory analyzing production and inspection records and failed samples, the complete machine customers also need to provide on-site data for joint analysis.
Only through joint efforts by both suppliers and buyers, identifying the true cause of the fuse's abnormal melting, can effective measures be taken to address the issue and prevent similar occurrences. This ensures that the fuse truly functions to melt promptly when needed, without causing trouble or even affecting production and usage due to abnormal melting.
