Snubber Circuit for Marine Controlled-Source Electromagnetic Transmitter

A high-power marine controlled-source electromagnetic transmitter (HP-MCSET) transmits a high-frequency conversion current on the sea floor. Some problems exist when the direct-current to alternating-current (DC-AC) launch bridge (LB) is used in the marine controlled-source electromagnetic transmitter (MCSET). There is a high voltage peak in the LB when the insulated gate bipolar transistor (IGBT) is turned on and off. In some cases, the voltage stress of the IGBT can be exceeded, which may cause IGBT damage. Because the rise of the current steepness is relatively low and the output voltage has a voltage peak in the LB, a snubber circuit is added to the IGBT to suppress the voltage peak to improve the output current and voltage waveform. The suppression of the voltage peaks is analyzed and compared for several groups of snubber circuits. To meet the performance requirements of the MCSET, the optimal snubber circuit is selected to effectively suppress the voltage peaks at an output current of 1 kA. This method is verified by using a 70 kW MCSET and the experimental waveforms are provided. The simulation of the inductance obstruction load in seawater is necessary to determine the conditions for actual marine environment experiments.