(1) False judgment

The melt is blown at the crimping or other parts, and there are generally no serious burn marks. The reasons for this may be: the melt section is too small; The melt has scar defects during installation; The fuse porcelain tray is not fixed; The melt crimping is not tight; The melt runs too long and produces a copper-aluminum oxide film, which increases the contact resistance. Normally, normal operation can be resumed with a suitable melt.

(2) Overload fusing

Usually the middle part of the melt is blown out, and there are few traces of arc burnout. At this time, the cause of overload should be found out to prevent overload.

(3) Short circuit fuse

The melt is severely burned, and arc burn marks remain on the porcelain tray of the fuse, which may be due to a short circuit fault between the zero line and the phase line or the phase line of the low-voltage side line. At this time, the low-voltage side lines and equipment powered by the transformer should be inspected, the short-circuit fault point should be found and eliminated, and then put back into operation. However, if there is a short circuit at the end of the line on the long low-voltage side, the melt burn may not be serious due to the large impedance and the small short-circuit current.

To eliminate the above reasons, after the transformer is put back into operation, even if the sound and appearance are normal, its secondary current should be tested, and if it significantly exceeds the rated value, the transformer should be stopped, and other reasons should be continued to be identified and dealt with, and then put into operation.