Constant-current control method of multi-function electromagnetic transmitter.
Based on the requirements of controlled source audio-frequency magnetotelluric, DC resistivity, and induced polarization, a constant-current control method is proposed. Using the required current waveforms in prospecting as a standard, the causes of current waveform distortion and current waveform distortion's effects on prospecting are analyzed. A cascaded topology is adopted to achieve 40 kW constant-current transmitter. The responsive speed and precision are analyzed. According to the power circuit of the transmitting system, the circuit structure of the pulse width modulation (PWM) constant-current controller is designed. After establishing the power circuit model of the transmitting system and the PWM constant-current controller model, analyzing the influence of ripple current, and designing an open-loop transfer function according to the amplitude-frequency characteristic curves, the parameters of the PWM constant-current controller are determined. The open-loop transfer function indicates that the loop gain is no less than 28 dB below 160 Hz, which assures the responsive speed of the transmitting system; the phase margin is 45°, which assures the stabilization of the transmitting system. Experimental results verify that the proposed constant-current control method can keep the control error below 4% and can effectively suppress load change caused by the capacitance of earth load.
College of Instrumentation and Electrical Engineering, Jilin University, Changchun 130021, China.
Kaichang
K
Xue
College of Instrumentation and Electrical Engineering, Jilin University, Changchun 130021, China.
Fengdao
F
Zhou
College of Instrumentation and Electrical Engineering, Jilin University, Changchun 130021, China.
Shuang
S
Wang
College of Instrumentation and Electrical Engineering, Jilin University, Changchun 130021, China.
Jun
J
Lin