Multiwaveform Current Transmitter for Induced Polarization Effects Surveying Based on the SQUID-TEM System

Abstract

The induced polarization effects magnetic field measurement method based on the superconductive quantum interfere device (SQUID) and transient electromagnetic (TEM) system can improve the exploration accuracy of metal minerals. As the core component of the SQUID-TEM system based on magnetic source, the current transmitter should reach consensus in three key aspects: high power, controllable turn-off time and combined current waveforms. In order to solve the problem of single transmitting current waveform and uncontrollable turn-off time in traditional current transmitter, a topology structure of current transmitter with multiple waveform combinations in time domain is proposed in this paper. By using the passive multi-group clamp technology and RLC series resonance technology, the falling edge turn-off time of trapezoidal and triangular transmitting current can be controlled, and the pulse width of semi-sinusoidal transmitting current can be adjusted. The laboratory and field experiments are implemented to test the performance of the current transmitter. Compared with the commercial PROTEM67 transmitter, the test results show that it can successfully transmit three current waveforms and their combination waveforms, the current amplitude is more than 100A, and the transmitting current turn-off time is controllable. The field measurement response results show that the combined multi-waveform transmit system can effectively measure the induction field and the polarization field generated by the Cole-Cole polarization ring, which provides technical support for the high-precision detection of induction-polarization effects based on the SQUID-TEM system.