Stepper motor driver is the main equipment of the cabinet of Absorption Sphere Shutdown System (ASSS) of High Temperature Gas-Cooled Reactor Pebble-Bed Modules (HTR-PM), which can control the stepper motor to act according to the preset value. If ASSS works abnormally due to the influence of interference, it will cause the stepper motor to run unexpectedly, which may cause the risk of the absorption sphere falling or refusing to fall by mistake and affect normal operation or nuclear safety of HTR-PM.

This study aims to formulate a scientific and reasonable anti-interference, so as to effectively reduce the pollution and impact of power grid and grounding system caused by pulse width modulation (PWM) mechanism, and avoid abnormal operation of stepper motor driver.

Through theoretical calculations and practical tests, the transmission path, mechanism and influence degree of interference caused by PWM were investigated, and customized optoelectronic isolation equipment was designed. Dedicated reactor and filter were installed on the transmission paths of the corresponding interference sources, hence effectively blocking the propagation interference and suppressing its impact, which was in the line with the unique working environment of the cabinet of the absorption sphere shutdown drive mechanism.

The anti-interference design scheme of drive cabinet in absorption sphere shutdown system effectively suppresses the impact of interference on the system, ensures the accurate and stable operation of the stepper motor driver, and realizes the angle deviation of the stepper motor within 1° for every 20 cycles operation, which effectively prevents the risk of malfunction of the stepper motor and improves the reliability of the system operation.

This design scheme has a good guiding significance for the anti-interference design of various control systems of the same type, and has certain promotion significance.