Determination of M-effect diffusion parameters in high breaking capacity fuses

The development of software models to simulate M-effect action in high breaking capacity fuses requires a knowledge of the diffusion process which occur between the M-effect alloy and the fuse element material during fuse operation. The authors describe the experimental determination of the diffusion parameters which dictate the rate of M-effect action, and their variation with temperatures. Diffusion data are obtained from fuse elements which have heat treated under both constant temperature and constant current conditions, and analysed using optical and scanning electron microscope techniques. Measurements from the micrographs enable both the diffusion coefficient and the activation energy of the silver-tin system to be determined. The values of the diffusion parameters so obtained are used in an electrical model for the M-effect, based on the use of analogue circuit simulation software package, to predict fuse temperature rise and the rate M-effect action, and the results obtained compared with experimental values