Solution of the electromagnetic noise produced from small electric appliance by real-time parallel measurements

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The purpose of the project is contro1 of electromagnetic noise generated from small electric appliances. A real-time parallel measurement system was developed for synthetic analysis of the phenomena of discahrge and noise generation of electric contacts. A progressive idea in this experiment is analysis of relationship of noise generation to the trace of arc discharge on the electrode surface. The conducting noise on the power line was measured for breaking contacts of two types. One is a Cu-C moving electric contact which simulates a pair of a commutator (Cu) and a brush (C) in a commutator motor in a small electric appliance, and the other is a Ag-Pd contact as a general heterogeneous electric contact.Waveforms of noise, voltage and current across the electric contact, and surface photograph of the electrode are measured in a simultaneous parallel way to analyze APD (amplitude probability distribution) of noise and the correlation in discharge phenomena. The phenomena of noise generation is classified into two patterns which are sporadic and continuous burst noise types depending on material condition. When a sporadic burst noise occurs, the trace of discharge on the electrode surface is formed in the noise duration, and we proposed that noise generation would be controllable by controlling formation of the discharge trace. When continuous noise occurs, the duration of large noise has correlation with the area or the discharge trace on the cathode surface for C-Cu, or the area of different color on the anode for Ag-Pd, respectively, and we proposed that arc duration should be controlled.An experiment showed that the noise duration could be reduced, by reducing the contact surface of electrodes for the sporadic burst noise, or by making the electrode thick in the case of the continuous burst noise. The result shows that the proposal that design of electrode shape is important in control of noise generation.