In high voltage great power frequency converter, great Electro Magnetic Interference EMI, caused by the power units, and insulation affect both veracity of transmitting signal and operating safety of units. 高电压大功率变频器中,功率器件引起的强电磁干扰环境以及绝缘的问题始终是变频器研究中影响测量信号准确性、器件运行安全性的一个问题。
When the vacuum circuit breaker ( VCB) turns on or off, it will result in the large spectrum and high frequency over-voltage due to the electromagnetic oscillations among equipment of the network, which will threaten the motor insulation, even the whole power system. 真空断路器在投合、断开高压电动机时,由于电网中的电气元件发生电磁振荡而形成幅值大、频率高的操作过电压,对电动机的绝缘造成威胁,影响电动机甚至整个传动系统的正常运行。
Mostly traditional passive noise control measures in automobile are vibration and sound insulation, noise elimination and sound absorption etc. These methods have good effect on the middle and high frequency noise, but little effect on low frequency noise caused by vibration and sound insulation of automotive body. 传统的噪声控制技术主要采用隔振、隔声、消声、吸声等方法来控制噪声,对降低中高频段噪声效果显著,但是对一些车身结构的振动及其辐射的低频噪声仍无法得到有效控制。
The result shows that static water contact angles on the three films are higher than 160 °. ( 3) Polyethylene has corrosion resistance, electrical insulation ( especially high frequency insulation), and is widely used in making corrosion resistant parts and insulation parts and film. 聚乙烯具有耐腐蚀性,电绝缘性(尤其高频绝缘性),广泛应用于制作耐腐蚀零件和绝缘零件及薄膜。
However, Pulse Width Modulation ( PWM) which was input from inverter is characterized by steep rising edge and high frequency, resulting in the too early failure of motor insulation. 然而,逆变器输出的PWM(脉冲宽度调制)连续高压脉冲的上升沿很陡、频率很高,导致在脉冲电压下牵引电机绝缘过早失效。
If the insulation system of inverter-fed motor stator worked long term under the high frequency steep square wave pulse voltage, the insulation would accelerate ageing, and the service life would shorten, which become the hidden trouble for the safety operation of high speed railway. 其定子绝缘系统长期工作在高频陡方波脉冲电压下,将导致绝缘加速老化、寿命缩短,成为高速铁路安全运营的隐患。