Dotan Cohen wrote: > On 15/11/2007, Mikkel L. Ellertson <mikkel@xxxxxxxxxxxxxxxx> wrote: >> The popping sound may be because of the RF spike when the contacts >> that turn on the heating element open or close. I have notices >> amplified speakers with long leads to the speakers tend to be >> sensitive to this. > > Do you say in English "induced current" when a changing magnetic field > causes current to flow? What is the correct English term? It is this > phenonenon to which I attribute the popping sounds. > Induced current is the proper tern, but I would expect a 60 cycle hum rather then a pop from induced current. I suspect that the pop is the wire between the computer and the speakers acting as an antenna, picking up the signal generated when the thermostat in the heater opens/closes, generating a small spark. (A spark-gap transmitter.) This is then amplified by the amp in the speakers. >> The things I would expect to cause problems are >> the microwave and the refrigerator. They both tend to have fairly >> high startup loads. This is known to cause a voltage drop. The >> extent of the drop depends on the wiring. also, depending on the >> type of fuse used, the spike may blow the fuse. Time delay fuses >> handle it best, fast blow fuses handle it the worst. I suspect that >> you have a time delay type fuse. > > I don't think that it's a time delay fuse because I recently did > something stupid, and it tripped right away. I've never heard of a > time delay fuse, but it sounds rather dangerous. > A time delay fuse is a dual element fuse that will accept a current spike without blowing, but will still blow at the rated current. Actually, a 10 amp fuse is only rated for 8 amps continues load. Mor then 80% of the fuse rating for more then an hour will cause the fuse to blow. The reason for time-delay fuses is to allow motor starting current, while still providing reasonable over-current protection. With a time delay fuse, you use a fuse that is 175% of the motor full load rating. with a non time-delay fuse, you normally need a fuse rated at 300% of the full load rating. So a time-delay fuse is actually safer for things like motor loads. They are also a good idea for any other loads that have a high startup current. It has been a long while sence I have used fuse ratings, but I would expect something like a NON for a non time delay and a FRN for a time delay fuse. But I am not sure if that is an international rating system. (I should know, but I have not needed this knowledge in a long time.) Mikkkel -- Black holes are where God divided by zero.
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