Miniaturizing Controlled-Source EM Transmitters for Urban Underground Surveys: A Bipolar Square-Wave Inverter...

Area of Science:

• Geophysics
• Electrical Engineering
• Electromagnetics

Background:

• Controlled-source Audio-frequency Magnetotelluric (CSAMT) surveys are crucial for subsurface exploration.
• Existing CSAMT transmitters can be bulky and inefficient, limiting their application in urban environments.
• Advancements in power electronics offer opportunities to improve transmitter design.

Purpose of the Study:

• To develop a compact and highly efficient electromagnetic transmitter for CSAMT applications.
• To reduce the size and weight of CSAMT transmitters for enhanced portability.
• To improve the efficiency and signal quality of CSAMT systems.

Main Methods:

• Proposed a novel bipolar square-wave inverter topology directly modulating the transformer's secondary-side AC output.
• Utilized a full-bridge bipolar inverter with SiC-MOSFETs and a high-frequency transformer.
• Conducted simulations, laboratory testing, and Electromagnetic Interference (EMI) evaluation.

Main Results:

• Achieved simulated efficiency greater than 90%.
• Reduced transmitter volume and weight by approximately 40%.
• Confirmed stable square-wave generation and compliance with EN55032 Class A EMI standards.
• Demonstrated effective signal transmission and high-resolution subsurface imaging in field tests.

Conclusions:

• The novel transmitter design significantly improves efficiency and portability for CSAMT surveys.
• The compact and efficient transmitter is well-suited for urban geophysical exploration.
• The technology meets stringent EMI standards, ensuring reliable field operation.