SUN De-li， SONG Shuang， TENG Fei
（College of Instrumentation & Electrical Engineering, Jilin University, Jilin 130061, China）
Abstract： Transient electromagnetic method (TEM) has been widely used in the field of medium and shallow underground detection due to its high detection efficiency and large detection depth. However, due to the long turn-off time of the transmitting current caused by the inductive characteristics of the transmitting coil, the early signals will be overwhelmed by primary field. Since the early signals contain most of shallow geological signals, it is necessary to reduce the long turn-off time to get shallow layer signal. Due to lack of a reliable and effective clamping method for high-power transmission at present, we design a TEM transmitter fast turn-off circuit, combining self-resonant zero-voltage switching technology with the corresponding timing control circuit to solve this problem effectively. A transient electromagnetic transmitter based on self-resonant constant voltage clamping technology was fabricated to charge the clamping capacitor. The rated transmitting current of the transmitter is 20 A, and the turn-off time is continuously adjustable from 550-50 μs. Moreover, the current drop process is approximately linear rather than exponential attenuation. Compared with the existing clamping methods, the proposed clamping method solves the problems that transient voltage suppressor (TVS) clamping cannot be used in high-power occasions and has a high failure rate. It also solves the problem of long pre-charge time in traditional capacitor clamping methods due to insufficient inductance of the small size transmitting coil. The proposed method can provide a reference for fast shutdown of large current.
Key words： transient electromagnetic method (TEM)； constant voltage clamp； zero voltage switch (ZVS)； linear turn-off
CLD number： TP273doi： 10.3969/j.issn.1674-8042.2020.03.014
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基于自谐振恒压钳位的线性快速关断技术
孙德立， 宋爽， 滕飞
（吉林大学 仪器科学与电气工程学院， 吉林 长春 130061）
摘要:瞬变电磁法（Transiant electromagnetic method, TEM）以其探测效率高、探测深度大等优点， 在中浅层地下探测领域得到了广泛的应用。 但由于发射线圈本身的电感特性， 导致发射电流的关断时间较长， 且发射电流激发的一次场将会淹没含有浅层地质信号的早期信号。 针对现有的瞬变电磁发射机存在的关断时间长， 大功率发射缺少可靠有效的钳位手段的现状， 设计了一种新的瞬变电磁发射机快速关断电路。 使用自谐振零电压开关技术向钳位电容充能， 同时设置相应的时序控制电路， 最终研制完成了基于自谐振恒压钳位技术的瞬变电磁发射机一台。 发射机额定发射电流20 A， 关断时间从550-50 μs连续可调， 电流下降过程近似线性， 不再按照一阶电路的指数规律下降。 与现有的钳位方式相比， 这种钳位方式解决了传统瞬态二极管（Transient voltage suppressor, TVS） 钳位不能用于大功率场合、 故障率高、 小尺寸发射线圈电感量不足造成使用储能电容钳位时预充电时间过长的问题。该技术为大电流快速关断提供了一种有效的方法。
关键词:瞬变电磁法； 恒压钳位； 零电压开关； 线性关断
引用格式：SUN De-li， SONG Shuang， TENG Fei. Linear fast shutdown technology based on self-resonant constant voltage clamping. Journal of Measurement Science and Instrumentation, 2020, 11（3）： 297-306. ［doi： 10.3969／j.issn.1674-8042.2020.03.014］
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