EMC

What is EMC?

EMC is short for electromagnetic compatibility. To avoid interferences during operation of machines or plants, checking and disclosure of EMC is mandatory. Some technical devices may create an electromagnetic field which may cause a negative interference for another device. Electromagnetic compatibility includes the interference a device may cause for other devices, as well as the tolerance in regards to interferences caused by other devices close by.

EMC capability of a device includes statements regarding interference immunity as well as emitted interference. Standards for both areas have been defined. A few examples are: EN 61000-6-2:2019 which describes interference immunity of devices and plants in the industrial sector and EN 50370-1:2006-02 which sets a standard of edited interference of machine tools. The requirements set in the standard regarding interference immunity are valid for a distinct frequency range.

EMC Capability in Laws and Standards

The necessary checks for evaluation of the electromagnetic capability are defined in standards and guidelines. On a European level the EMC-Guideline of the EU (Guideline 2014/30/EU regarding electromagnetic capability) is to be applied. In Germany this standard is applied in the EMVG (Short for „Gesetz über die elektromagnetische Verträglichkeit von Geräten“, en: "Law regarding electromagnetic capability of devices").

Within the EMVG, the term "device" includes components that emit electro-magnetic interference or are affected by it. Additionally, products that may be used independent as well as mobile facilities that consist of a number of different devices are included. The term "device" (de: "Betriebsmittel") is used regarding fixed EMVG devices or stationary facilities.

Electromagnetic Capability and CE-Marking

If a product is marked with the CE-Marking, the manufacturer indicates that this product is in compliance with corresponding EU guidelines. This includes the EMC-Guideline. Even if all individual devices are CE-Compliant, it is not a given that all devices together as a unit are EMC capable. Additional checks to ensure the electromagnetic capability of the facility may be necessary. EN 61000-6 is the generic standard for CE assessment of conformity.

EMC disturbance variables and checks

The series of standards EN 61000-4-x include the conditions for checking disturbance variables. The disturbance variables include: discharge of static electricity (EN 61000-4-2), high frequency electromagnetic fields (EN 61000-4-3) and Burst (fast transient interferences). Additionally surge voltage and impulse shaping magnetic fields are also defined as disturbance variables. Checks for resistance to voltage fluctuations and asymmetric supply voltage are defined in additional generic standards of these series.

Disturbance variable can be either grid bound or field bound. The connection between the device causing the disturbance (source) and the device affected by it is called the interconnection. There are capacitive as well as inductive interconnections that might cause EMC disturbances.

The check result is split up into criteria which describe the reaction to different disturbance variables during and after the check process. To fulfil certain criteria it may be sufficient if a device does not function during the EMC check and functions without issues afterwards.

EMC Measures

To assure EMC capability of machines and plants, effective measures should be applied. These measures should not compromise the functionality of the system or exceed the given budget. The responsible engineer has a choice of a number of different measures. EMC guidelines describe these measures. The manual for application of guideline 2004/108/EG contains a detailed explanation for the application of the EMC guideline and the terms defined in it.

Practical measures include the coating of devices, cases and lines. Plug-in connectors have to be constructed EMC capable. Surge protection and grounding are additional measures to be considered when evaluating EMC measures. Inside and outside the control cabinet, EMC measures to avoid interference should be applied as well.