Transmitter is the key equipment for electromagnetic exploration of ground artificial source.Under the same transmitting current condition,the larger the pole distance and the higher the signal-to-noise ratio,the better the detection effect.The long wire required for large pole distance has strong inductance(about 3 mH inductance of the 1 km wire).The current turn-off time of the 3 mH inductor is about 103.95 μs under the condition of 1000 V transmitting voltage and 50 A transmitting current.For electromagnetic exploration in the time domain,the signal-to-noise ratio of the observed signal,which is inversely proportional to the logarithm of the turn-off time,improved by 10 dB with the turn-off time decreases 10 times.In this paper,by adding a fast turn-off unit to the transmitting loop and introducing an auxiliary turn-off voltage to form a current high-voltage release loop,the turn-off time under the condition of 1 km long wire is expected to be less than 10 μs,and the signal-to-noise ratio of observed data is increased by more than 10 dB,which has important theoretical significance and engineering value.
Electromagnetic exploration transmitterLarge pole distanceLong wireParasitic inductanceFast current turn-off
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