Influence of Parasitic Capacitance on Turn-Off Current and Its Optimization Method for Transient Electromagnetic System

In transient electromagnetic (TEM) inverter circuits, a damping resistor is typically connected in parallel to the transmitting coil to prevent overshoot during the turn-off period of the pulse current. This configuration results in an exponential decay waveform for the pulse current, which prolongs the turn-off time and increases the nonlinear error. This article analyzes the impact of the parasitic capacitance on the value of the damping resistor and the end-period waveform of the pulse current base on the inverter circuits, and proposes an optimized control method to reduce both the turn-off time and the nonlinear error of the pulse current. The method is validated through the construction of an experimental circuit. According to the experimental data, this optimization method reduces the turn-off time by 23.8% and the nonlinear error by 5.5%. In the unexploded ordnance (UXO) detection experiment, the optimization method's detection results exhibit higher resolution.