一种改善瞬变电磁发射电流波形的系统设计

为了减小瞬变电磁发射机发射电流的关断时间,保证发射电流关断沿的线性度,抑制关断后电流过冲,简化钳位电压电路,设计了一种简便的瞬变电磁发射系统。提出了一种利用TVS管和电容相结合的恒压钳位电路并采用传统的在负载两端并联匹配电阻的吸收方式。通过调节TVS管的稳压值,可以调节关断时间和关断沿斜率;选择直接在负载两端匹配合适电阻,保证了关断前期处于欠阻尼状态,关断后期处于临界阻尼状态,在快速关断的前提下,有效防止关断后电流过冲,达到了改善发射电流波形的目的。实验结果表明,该系统电路结构简单、稳定、易于实现,在短关断延时、关断沿线性化和关断后无过冲方面,得到明显改善。

Design of a system for improving the wave of transmit current in transient electromagnetic method

In order to reduce the transmit current off-time of the transient electromagnetic transmitter and ensure the linearity of off-edge in transmit current, restrain the current overshoot after shutting down, simplify the clamping volt-age circuit, a simple transient electromagnetic transmitting system is designed.This paper puts forward a constant voltage clamping circuit which is combined by TVS tubes and capacitors, and the traditional way of a matching resistor in parallel with the across of the load is used in the circuit.By adjusting the voltage value of the TVS tube, shut-off time and the linearity of off-edge can be adjusted.Through matching the appropriate resistors across the load directly, which ensure that the pre-shutdown is in underdamped and the late of shutdown is in critically damped.It can effec-tively prevent the current from overshooting after shutting down and achieve the purpose of improving the waveform of transmit current under the premise of fast turn-off.The results show that the circuit structure of the system is simple, stable and easy to implement.Three key indicators are significantly improved in the aspects of reducing the off-time of transmit current, ensuring the linearity of off-edge in transmit current, restraining the current from overshooting after shutting down.