An experimental system of AC arc discharge in water was designed with pole-pole electrodes and a peak voltage of 1500 V and a test circuit was set up using virtual instrument technology. The mechanism of an AC plasma arc generated in water was analyzed. The voltage- current characteristic of the AC plasma are was obtained from the waveform. The temperature characteristic was tested with a spectrum diagnosis system, and the effect of different electrode materials on the striking voltage and peak current was analyzed. The results show that when a power supply of 6 kW is applied on electrodes with a gap of 2 mm in water, the striking voltage is from 900 V to 1300 V, the arc voltage is from 40 V to 100 V, the arc current is from 2 A to 7 A, and the zero rest period is from 1 ms to 2 ms. In addition, the arc voltage and current are different for electrodes in aluminum, copper and stainless steel. The arc voltage is lower and the current is higher for an aluminum electrode than those for copper and stainless steel ones. The highest temperature of the arc is 7643 K.
磁悬浮球作为质量块实现惯性式振动测量,测量磁悬浮球与测振系统壳体的相对位移即可得到被测振动体的振动参数。由于磁悬浮球不与任何物体接触、无机械摩擦、无机械间隙误差,与传统惯性式振动测量方法相比具有灵敏度高、测量上限频率高,直接输出振动位移信号,通过微加工技术可实现体积小等优点,控制电路还可提供各类所需阻尼函数,但低于10 H z测量频率时需加大测试装置尺寸。在构建磁悬浮球模型及控制系统的基础上,通过对系统的结构和运行参数分析,推导了磁悬浮测振系统动力学方程,并将其等效成表征质量-弹簧测振系统的常系数二阶微分方程,使等效阻尼系数和刚度系数与质量-弹簧系统的参数有一定的对应关系。通过标准激振器产生不同的振动信号,测量结果验证了该方法正确。测试系统灵敏度:986 mV/g,测量频率范围:20 H z^5 kH z。该方法无需粘贴传感器、性价比高、操作方便。
