As the core triggering and control unit in rectification or conversion systems, the Modular Thyristor Control module (MTC module) plays a critical role in maintaining the safe and stable operation of thyristor-based power conversion equipment. Therefore, timely non-destructive testing of thyristor devices is essential for effective health management and risk prevention. This study conducts both theoretical and experimental analyses of the electromagnetic voiceprint (EMVP) signals generated during thyristor operation, aiming to explore the feasibility and application potential of EMVP -based condition monitoring. Theoretical analysis reveals that during the thyristor turn-on process, rapid variations in the electromagnetic field—induced by current positive feedback—are the primary source of EMVP signals. In contrast, during natural commutation at the current zero-crossing point, the gradually changing electromagnetic field fails to generate significant EMVP responses. EMVP signals were captured using acoustic emission (AE) instrumentation under various firing angles, turn-on current magnitudes, and sensor positions. Time-domain and frequency-domain analyses were performed to investigate the characteristics and evolution of these signals. This provides a robust methodological foundation for future EMVP-based non-invasive diagnosis and health status evaluation of thyristor modules.