1. Laboratory of Geophysical EM Probing Technologies, MLR, Langfang 065000, China 2. Institute of Geophysical and Geochemical Exploration, CAGS, Langfang 065000, China
In the CSAMT survey, the inductive on transmitting circuit wire increases with the increasing frequency of the transmitting signal. When the power supply voltage and grounding resistance is constant, the transmitting current will drop with the increasing frequency of the transmitting signal, so the received signal in the receiver becomes weak, and the exploration effect is seriously affected. In this paper, by analyzing the impedance characteristics of the transmitting circuit and RCL series resonant circuit and simulating the amplitude and frequency characteristic curve of transmitting circuit which adds the different value compensating capacitors, the authors proved that it is possible to increase the transmitting current of the high frequency signal by adding the different compensation capacitor in the transmitting circuit. On such a basis, the authors designed electrical source CSAMT transmitter based on compensation capacitors technology. Through the high and low frequency signal transmitting, the transmission circuit impedance is determined, then in the transmission process it can be sent with the signal frequency changes and the compensation capacitor is constantly adjusted to achieve effective increase of high frequency band send current. In the working process, first the test method is used to determine the impedance of the transmitting circuit, and then the transmitter will automatically adjust the capacitor compensation network switch with the changing of the frequency of the transmitting signal, the different compensation capacitors are switched into the transmitting circuit to achieve the transmitting current increases. The scheme was tested and verified in practice. The recorded data show that the current in the high frequency area is improved obviously after the compensating capacitor is connected in transmitting circuit. It is expected that this method will enhance the transmitting current of the high frequency area and improve the observation data quality of CSAMT.
Yu F, Zhang Y M . Modeling and control method for high-power electromagnetic transmitter power supplies[J]. Journal of Power Electronics, 2013,13(4):679-691.
doi: 10.6113/JPE.2013.13.4.679