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静电放电,传导干扰,电磁兼容,耦合辐射

日期:2018-01-08浏览:1830次

The phenomenon of electromagnetic interferences
Depending on the kind of coupling of electromagnetic disturbances the phenomenon are divided into two different groups. In case the disturbance signal is air-borne one speaks of radiated interference while in case of disturbance signals are line-carried one speaks of conducted interference.

Where the coupling is radiation
Stationary and non-stationary radio transmitters (Electrical Field)
Both stationary high-power radio transmitters and non-stationary walkie-talkies or ecommunication devices operating in the immediate vicinity of systems or equipment lead to uncontrolled electromagnetic radiation into vulnerable electronic equipment.
Parameters: Narrow-band, continuous electromagnetic interference (modulated).
Standard reference: IEC/EN 61000-4-3 

HV power supply transmission lines (Magnetic Field) 
In the close vicinity to these lines high magnetic fields can be generated and coupled into other electronic or electrical systems.
Parameters: Narrow-band with 16 2/3Hz or 50/60Hz, continuous electromagnetic interference
Standard reference: IEC/EN 61000-4-8 

Indirect lightning effects (pulsed Magnetic Field) 
Lightning strokes into HV voltage power distribution systems are causing high electromagnetic fields which are able to cause induced voltage in any low voltage distribution system, such as power mains systems. Also ecom networks, due to the extended distribution of cabling, are threatened by indirect lightning effects.
Parameters: Range of voltage some tens of kilovolts, range of current some hundreds of amps, high-energy pulses with rise times in the microsecond range.
Standard reference: IEC/EN 61000-4-9


Where the coupling is conduction
Inductive load switching results in Electrical fast transients (burst)
Electromagnetic influences produced in the neighborhood by rapid variation of voltage and current as a result of the abrupt change of a switch from a non-conductive to a fully conductive status or vice versa, e.g. switching inductive loads with mechanically moved contacts between which arcing occurs before they separate.
Parameters: Broad-band pulse interference, rise time of pulses of a few nanoseconds, small energy content and high repetition rate.
Standard reference: IEC/EN 61000-4-4 

Switching inductive or capacitive loads in power mains supply system 
Switching heavy inductive or capacitive loads in low voltage power mains supply systems are causing transients of high energy and high voltage, depending on the installation category.
Parameters: Range of voltage some up to tens of kilovolts, range of current some tens of kilo amps, high-energy pulses with rise time and duration in the microsecond range.
Standard reference: IEC/EN 61000-4-5 

Atmospheric discharges such as lightning 
Lightning strokes into high voltage power distribution systems are causing transients in low voltage power mains networks. Via coupling these transients can also be detected in data bus systems, I/O lines and any cabling in the industrial area.
Parameters: Range of voltage some tens of kilovolts, range of current some tens of kilo amps, high-energy pulses with rise times in the microsecond range.
Standard reference: IEC/EN 61000-4-5 

Power Mains supply failures 
Voltage dips and short interruptions are caused by faults in the network, in installations or by a sudden large change of load. In certain cases, two or more consecutive dips or interruptions may occur. Voltage variations are caused by continuously varying loads connected to the mains supply network.
Parameters: These phenomena are random in nature and can be characterized in terms of the deviation from the rated voltage and duration.
Standard reference: IEC/EN 61000-4-11 

Electrostatic discharge 
ESD occurs when the static electric field between two objects exceeds the dielectric strength of the air between them. The discharge is a complex event involving a local transfer of charge at the point of discharge, electromagnetic near field coupling between the objects involved, induced current flow in the object receiving the discharge and radiated electromagnetic energy from the charged object as well as from the arc of the discharge. All of these phenomenon are capable of causing malfunctions and, in some cases, damage in electronic equipment.
Parameters: The major effects are generated by the discharge current (< 100A) and voltage (< 30kV) with rise times in the nanosecond and even in the picosecond range.
Standard reference: IEC/EN 61000-4-2 

Conducted disturbances, induced by radio-frequency fields 
Conducted radio-frequency disturbance occurs from intended rf transmitters affecting cables such as mains supply lines, signal lines or earth connections between different parts of an electrical or electronic systems.
Parameters: The interference signal is a an amplitude modulated or pulse modulated signal, typically in the frequency range between 9kHz and 80MHz, sometimes extended to 230MHz.
Standard reference: IEC/EN 61000-4-6 

Harmonic current emission 
With an increasing number of electronic power supplies used in a wide range of products the aim to limit the harmonic current emission has become more and more important. It is a specific interest of the power distribution companies to keep the harmonic current emission to a considerable low level as harmonic current causes unnecessary loading of the power distribution infrastructure. This again may affect both quality and reliability of the power supply.
Parameters: Harmonic currents are measured up to the 40th harmonic of the fundamental. Limits for each harmonic are specified depending on the type of product.
Standard reference: IEC/EN 61000-3-2, IEC/EN 61000-3-12 

Voltage changes, voltage fluctuation and flicker 
During an entire duty-cycle of a product sudden voltage changes, voltage fluctuations or flicker might occur. This may effect the quality of the mains supply voltage. Flicker can be visually recognized as the illumination strength of a lamp may drop significantly even for a very short time. To keep such phenomenon to the minimum limits have been introduced for the impact of load variations to the public mains supply network.
Standard reference: IEC/EN 61000-3-3, IEC/EN 61000-3-11


Additional Phenomena - EMC in Vehicles
Apart from the basic phenomena as described here above a wide range of additional requirements can be found for special electrical and electronic systems such as vehicles. These requirements are based on the fact that within a vehicles supply system a large number of sub-systems and components are installed generating interference and at the same time being exposed to interference. Some of the phenomena that can be found on-board vehicles look similar to the ones that are specified in the basic standards of IEC. Some are specific for thes systems.

Many vehicle manufacturers have set up their own EMC requirements for both conducted and radiated immunity and emission testing。 These requirements supersede the national and international standards existing for EMC testing on vehicles (e。g。 ISO7637, SAE J1113, JASO)。

电磁干扰现象
根据电磁干扰的耦合类型,这种现象被分成两个不同的组。如果干扰信号是空气传播的,可以说是辐射干扰,而当干扰信号是带线的时,则说传导干扰。

耦合辐射的地方
固定和非平稳无线电发射机(电场)
固定大功率无线电发射机和非平稳的对讲机或移动通信设备立即系统或设备附近操作导致不受控制的电磁辐射为脆弱的电子设备。
参数:窄带,连续电磁干扰(调制)。
参考标准:IEC / EN 61000-4-3

高压电源传输线(磁场)
在这些线附近,可以产生高磁场并耦合到其他电子或电气系统中。
参数:16 2 / 3hz或50/60Hz频带窄,连续的电磁干扰
参考标准:IEC / EN 61000-4-8

间接闪电效应(脉冲磁场)
高压高压配电系统的雷击引起了高电压的电磁场,它能在任何低压配电系统,如电力系统中引起感应电压。此外,由于布线的广泛分布,电信网络也受到间接闪电效应的威胁。
参数:电压伏数范围内,目前有数百安培范围,在微秒范围内的高能脉冲上升时间。
参考标准:IEC / EN 61000-4-9


耦合在传导的地方
感应负载开关导致电快速瞬变(猝发)
由于开关从非导电到完全导电状态的突然变化而引起的电压和电流的快速变化,在邻近地区产生电磁影响,例如在机械分离触点上切换感应负载,在它们分开之前发生电弧。
参数:宽带脉冲干扰,对几纳秒脉冲的上升时间,小的能量含量和高重复率。
参考标准:IEC / EN 61000-4-4

电源系统中开关感性负载或电容性负载
在低压电源系统中切换重感性或容性负载,会引起高能量和高电压的瞬变,这取决于安装类别。
参数:电压有的高达几十千伏的范围内,电流安培数公斤的一些范围,在微秒范围内的高能脉冲上升时间和持续时间。
参考标准:IEC / EN 61000-4-5

大气放电,如闪电
高压配电系统的雷击导致低压电网的瞬变。通过耦合,这些瞬变也可以在数据总线系统、I/O线和工业区的任何布线中检测到。
参数:电压伏数范围内,电流安培数公斤的一些范围,在微秒范围内的高能脉冲上升时间。
参考标准:IEC / EN 61000-4-5

电源故障
电压骤降和短时中断是由网络故障、装置故障或突然大负荷变化引起的。在某些情况下,可能发生两次或多次连续的骤降或中断。电压变化是由于不断变化的负载连接到电源供应网络引起的。
参数:这些现象本质上是随机的,可以用额定电压和持续时间的偏差来表征。
参考标准:IEC / EN 61000-4-11

静电放电
静电放电发生在两个物体之间的静电电场超过它们之间的空气的介电强度时。放电是一个复杂的事件,包括在放电点的局部电荷转移,涉及对象之间的电磁近场耦合,接收物体的感应电流,从带电物体和放电电弧发射电磁能量。所有这些现象都会导致故障,在某些情况下也会损坏电子设备。
参数:主要作用是通过电流产生的(小于100A)和电压(<30kV)上升时间在纳秒甚至皮秒范围。
标准:参照IEC/EN 61000-4-2

射频场引起的传导骚扰
传导无线电频率干扰来自预期的射频发射机影响电缆,如电力供应线、信号线或电气或电子系统不同部分之间的地线连接。
参数:干扰信号是一个振幅调制或脉冲调制信号,通常在9kHz和80MHz的频率之间的频率范围,有时扩展230 MHZ。
参考标准:IEC / EN 61000-4-6

谐波电流发射
随着越来越多的电子电源应用于广泛的产品,限制谐波电流发射的目标变得越来越重要。由于谐波电流对配电网基础设施造成不必要的负荷,使配电网的谐波电流降到相当低的水平是电力企业的一个特殊利益。这又可能影响电源的质量和可靠性。
参数:谐波电流测量到基波的第四十谐波。每个谐波的限制取决于产品的类型。
参考标准:IEC / EN 61000-3-2标准,IEC / EN 61000-3-12

电压变化,电压波动和闪变
在产品的整个工作周期内,可能突然发生电压变化、电压波动或闪变。这可能会影响电源供电电压的质量。闪烁可以在视觉上被识别,因为灯的照明强度即使在很短的时间内也会显著下降。为了使负荷变化对公共供电网络的影响,必须将这种现象保持在zui低限度。
参考标准:IEC / EN 61000-3-3,IEC / EN 61000-3-11


附加现象-车辆电磁兼容性
除了如上所述的基本现象外,对于特殊的电气和电子系统,如车辆,也可找到广泛的附加要求。这些要求基于这样一个事实:在车辆供应系统中,安装了大量的子系统和组件,产生干扰,同时又受到干扰。在车载车辆上发现的一些现象与IEC标准中所规定的类似。有些是专为这些系统。

许多汽车制造商已经建立了自己的EMC要求进行传导和辐射免疫力和排放测试。这些要求取代现有的国家标准和国际标准EMC测试车辆(如ISO7637,SAE j1113,JASO)。

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