In this paper, we measured the armature velocity of an experimental electromagnetic launcher by B-dot method and analyzed the change of the armature's average speed. The electromagnetic gun launching process was also simulated by Ansoft Maxwell simulation software. The launch current is used as the model's excitation which means that the current in the model is the same as the rail current. Ansoft Maxwell's 3D model can accurately simulate the launching process, in theory. We found that there was an unexpected rise during the real launching process. The phenomenon can be discovered in the following several experiments. We analyzed several possible causes such as the inductive gradient change, rail broken and inaccurate measurement of B-dot probe. The inductive gradient is an important parameter in the launching process and can affect the armature speed. After checking the measurement problem, we also found that the wave form of the output signal from the probe where the unexpected change occurred was normal but the amplitude was very small. The measurement method was proved correct. The rise of average inductance gradient leads to the unexpected increase in average speed and the small signal. Furthermore, the physical reason for the change of inductance gradient should be the change of current distribution. © 2021 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

中文翻译：

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试验型轨道发射器电枢平均速度变化分析

在本文中，我们用B-dot法测量了一个实验电磁发射器的衔铁速度，并分析了衔铁平均速度的变化。电磁炮发射过程也由Ansoft Maxwell仿真软件进行模拟。启动电流用作模型的激励，这意味着模型中的电流与轨电流相同。Ansoft Maxwell 的 3D 模型理论上可以准确模拟发射过程。我们发现在真正的上线过程中出现了意外的上涨。这种现象可以在以下几个实验中发现。我们分析了电感梯度变化、断轨、B-dot探头测量不准确等几种可能的原因。感应梯度是发射过程中的一个重要参数，会影响电枢速度。在检查测量问题后，我们还发现发生意外变化的探头输出信号的波形是正常的，但幅度很小。测量方法被证明是正确的。平均电感梯度的上升导致平均速度和小信号的意外增加。此外，电感梯度变化的物理原因应该是电流分布的变化。© 2021 日本电气工程师学会。由 Wiley Periodicals LLC 出版。我们还发现，发生意外变化的探头输出信号的波形是正常的，但幅度很小。测量方法被证明是正确的。平均电感梯度的上升导致平均速度和小信号的意外增加。此外，电感梯度变化的物理原因应该是电流分布的变化。© 2021 日本电气工程师学会。由 Wiley Periodicals LLC 出版。我们还发现，发生意外变化的探头输出信号的波形是正常的，但幅度很小。测量方法被证明是正确的。平均电感梯度的上升导致平均速度和小信号的意外增加。此外，电感梯度变化的物理原因应该是电流分布的变化。© 2021 日本电气工程师学会。由 Wiley Periodicals LLC 出版。