CE Marking and RFI Filters

The CE Mark

As of January 1, 1996, electrical and electronic equipment shipped to Europe is required to be labeled with the CE marking. In order to apply the CE marking, equipment must meet the General Product Safety Directive and Electromagnetic Compatibility Directive.

The intent of the General Product Safety Directive 92/59/EEC is that product placed on the European market be safe. Compliance may be shown by obtaining approval to the product's appropriate safety standard, such as EN 60950 for information technology equipment.

According to the "Guidelines on the Application of Council Directive 73/23/EEC", components should not be CE marked. This is because a component's safety depends on its use in the final product. Although a component may be approved to the applicable safety agency standard, it must also be verified to comply with the requirements of the system standard submitted within to be proclaimed safe in its use.

Product that either causes or is susceptible to interruption by electromagnetic interference is required by the Electromagnetic Compatibility Directive 89/336/EEC to meet the emission and immunity specifications outlined in the Official Journal of the European Communities.

RFI power line filters are components and therefore not covered by the CE requirements, but they are used in electronic systems to meet EMC specifications. It is not mandatory for the RFI filter to be approved by a European safety agency, but an approval by a safety agency such as VDE in Germany would eliminate delays in testing the RFI filter for safety requirements at the system level.

Two of the most common emission specifications are EN 55011 for industrial, science, and medical equipment, and EN 55022 for information technology equipment. The conducted emission limits for these specifications are the same and broken down into class "A" and class "B" limits. Electronic equipment that may be connected to a power main shared with a residential area must comply with the more stringent class "B" limits. The measurement technique is done using quasi-peak and average detection, with different limits for each, measured in dB above one microvolt.

* (limit decreasing with log of frequency)

There are several immunity tests that electronic equipment must comply to, one of which is the electrically fast transient, IEC 1000-4-4. The equipment must continue to operate during this test. The transient wave form is a 5ns rise time with a 50ns duration. A burst is induced onto the power line at 1kV with a repetition rate of 5kHz lasting 15ms and repeated every 300ms. The test simulates switching of inductive loads and contacts.

To pass the EFT test, it is important that the RFI filter's enclosure have a good RF ground with the system's chassis ground. This provides a low impedance path from the safety ground to the system ground. The shielding effect of the RFI filter's metal enclosure eliminates radiation into the system's cabinet induced by the conducted EFT burst. Stray capacitance may occur from any of the three input power wires to chassis ground where voltage can build up from the EFT burst and cause system interrupts. The RFI filter's inductor offers an impedance to the burst.

In cases where the stray capacitance's have caused multiple RF ground planes or where plastic system enclosures are used, an inductive choke may be needed to provide isolation of the safety ground from the chassis ground.

A system is subjected to many other tests in order to gain CE compliance. Those mentioned here apply to the use of RFI power line filters.