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).

電磁干擾現象
根據電磁干擾的耦合類型，這種現象被分成兩個不同的組。如果干擾信號是空氣傳播的，可以說是輻射干擾，而當干擾信號是帶線的時，則說傳導干擾。

耦合輻射的地方
固定和非平穩(wěn)無線電發(fā)射機（電場）
固定大功率無線電發(fā)射機和非平穩(wěn)的對講機或移動通信設備立即系統(tǒng)或設備附近操作導致不受控制的電磁輻射為脆弱的電子設備。
參數：窄帶，連續(xù)電磁干擾（調制）。
參考標準：IEC / EN 61000-4-3

高壓電源傳輸線（磁場）
在這些線附近，可以產生高磁場并耦合到其他電子或電氣系統(tǒng)中。
參數：16 2 / 3hz或50／60Hz頻帶窄，連續(xù)的電磁干擾
參考標準：IEC / EN 61000-4-8

間接閃電效應（脈沖磁場）
高壓高壓配電系統(tǒng)的雷擊引起了高電壓的電磁場，它能在任何低壓配電系統(tǒng)，如電力系統(tǒng)中引起感應電壓。此外，由于布線的廣泛分布，電信網絡也受到間接閃電效應的威脅。
參數：電壓伏數范圍內，目前有數百安培范圍，在微秒范圍內的高能脈沖上升時間。
參考標準：IEC / EN 61000-4-9

耦合在傳導的地方
感應負載開關導致電快速瞬變（猝發(fā)）
由于開關從非導電到*導電狀態(tài)的突然變化而引起的電壓和電流的快速變化，在鄰近地區(qū)產生電磁影響，例如在機械分離觸點上切換感應負載，在它們分開之前發(fā)生電弧。
參數：寬帶脈沖干擾，對幾納秒脈沖的上升時間，小的能量含量和高重復率。
參考標準：IEC / EN 61000-4-4

電源系統(tǒng)中開關感性負載或電容性負載
在低壓電源系統(tǒng)中切換重感性或容性負載，會引起高能量和高電壓的瞬變，這取決于安裝類別。
參數：電壓有的高達幾十千伏的范圍內，電流安培數公斤的一些范圍，在微秒范圍內的高能脈沖上升時間和持續(xù)時間。
參考標準：IEC / EN 61000-4-5

大氣放電，如閃電
高壓配電系統(tǒng)的雷擊導致低壓電網的瞬變。通過耦合，這些瞬變也可以在數據總線系統(tǒng)、I/O線和工業(yè)區(qū)的任何布線中檢測到。
參數：電壓伏數范圍內，電流安培數公斤的一些范圍，在微秒范圍內的高能脈沖上升時間。
參考標準：IEC / EN 61000-4-5

電源故障
電壓驟降和短時中斷是由網絡故障、裝置故障或突然大負荷變化引起的。在某些情況下，可能發(fā)生兩次或多次連續(xù)的驟降或中斷。電壓變化是由于不斷變化的負載連接到電源供應網絡引起的。
參數：這些現象本質上是隨機的，可以用額定電壓和持續(xù)時間的偏差來表征。
參考標準：IEC / EN 61000-4-11

靜電放電
靜電放電發(fā)生在兩個物體之間的靜電電場超過它們之間的空氣的介電強度時。放電是一個復雜的事件，包括在放電點的局部電荷轉移，涉及對象之間的電磁近場耦合，接收物體的感應電流，從帶電物體和放電電弧發(fā)射電磁能量。所有這些現象都會導致故障，在某些情況下也會損壞電子設備。
參數：主要作用是通過電流產生的（小于100A）和電壓（＜30kV）上升時間在納秒甚至皮秒范圍。
標準：參照IEC/EN 61000-4-2

射頻場引起的傳導騷擾
傳導無線電頻率干擾來自預期的射頻發(fā)射機影響電纜，如電力供應線、信號線或電氣或電子系統(tǒng)不同部分之間的地線連接。
參數：干擾信號是一個振幅調制或脈沖調制信號，通常在9kHz和80MHz的頻率之間的頻率范圍，有時擴展230 MHZ。
參考標準：IEC / EN 61000-4-6

諧波電流發(fā)射
隨著越來越多的電子電源應用于廣泛的產品，限制諧波電流發(fā)射的目標變得越來越重要。由于諧波電流對配電網基礎設施造成不必要的負荷，使配電網的諧波電流降到相當低的水平是電力企業(yè)的一個特殊利益。這又可能影響電源的質量和可靠性。
參數：諧波電流測量到基波的第四十諧波。每個諧波的限制取決于產品的類型。
參考標準：IEC / EN 61000-3-2標準，IEC / EN 61000-3-12

電壓變化，電壓波動和閃變
在產品的整個工作周期內，可能突然發(fā)生電壓變化、電壓波動或閃變。這可能會影響電源供電電壓的質量。閃爍可以在視覺上被識別，因為燈的照明強度即使在很短的時間內也會顯著下降。為了使負荷變化對公共供電網絡的影響，必須將這種現象保持在zui低限度。
參考標準：IEC / EN 61000-3-3，IEC / EN 61000-3-11

附加現象-車輛電磁兼容性
除了如上所述的基本現象外，對于特殊的電氣和電子系統(tǒng)，如車輛，也可找到廣泛的附加要求。這些要求基于這樣一個事實：在車輛供應系統(tǒng)中，安裝了大量的子系統(tǒng)和組件，產生干擾，同時又受到干擾。在車載車輛上發(fā)現的一些現象與IEC標準中所規(guī)定的類似。有些是專為這些系統(tǒng)。

許多汽車制造商已經建立了自己的EMC要求進行傳導和輻射免疫力和排放測試。這些要求取代現有的國家標準和標準EMC測試車輛（如ISO7637，SAE j1113，JASO）。