Time-Domain Analysis of Arc Voltage and Electromagnetic Noise Caused by Opening Arc Discharge between Carbon and Copper Contacts

摘要

In small commutation motors, arc discharges are generated between the brushes (carbon) and commutators (copper) in opposing positions, accompanied by electromagnetic noise. An arc discharge is produced both between the brush and commutator (Cu cathode) and between the commutator and brush (C cathode), and these two phenomena with different polarities cannot be separately observed from outside. In this investigation the arc discharges of different current polarities and their associated noise characteristics are analyzed. Experiments are performed with different opposing electrodes, consisting of C and Cu. The opening voltage is 40 V DC. The current in the closed state is 2 A. The load is an inductance of 0.85 mH. The arc voltage and noise when the electrical contacts are opened in both the Cu cathode and C cathode cases are analyzed as time series. It is found that the maximum noise level in each operation is about 20 dB higher for the Cu cathode case than for the C cathode case. The time of maximum noise generation in each operation is close to the time of arc extinction for the Cu cathode case but is in the middle of the arc discharge for the C cathode case. The time derivative of the voltage waveform near arc extinction and the amplitude of the noise waveform before detection are larger in the Cu cathode case than in the C cathode case.