Test Equipment

Power Frequency Magnetic Field

Electronic products are often subjected to magnetic fields at AC mains frequencies. These fields are frequently produced in the vicinity of power transformers and can cause problems with video displays, Hall effect sensors, and other electronic products having a sensitivity to magnetic fields.

Electronic Products are tested for immunity to power frequency magnetic fields to insure their continued reliable operation when placed in service. The European Union's EMC Directive currently mandates power frequency magnetic field testing for certain categories of equipment as a condition for obtaining the CE Mark before shipping products to member states of the European Union.

Applicable Standards

Generic Immunity, Product and Product Family Standards require that Power Frequency Magnetic Field tests be performed in accordance with Basic EMC Standards: IEC 61000-4-8 and EN 61000-4-8. Application Note, EMC Standards Overview, provides an overview of European Standards for electromagnetic compatibility, describes how the Standards relate to one another, and list sources for procuring copyrighted documents.

Basic EMC Standard

The Basic EMC Standard for Power Frequency Magnetic Field defines methods of generating consistently reproducible magnetic fields for test purposes. Although higher magnetic field levels are described, compliance to the Generic Immunity Standard for residential and commercial products is 1A/m or 3A/m. Currently applicable only to apparatus containing devices susceptible to magnetic fields, testing of other products may be required to make that determination. While the Basic EMC Standard specifies how to perform Power Frequency Magnetic Field testing, the Generic, Product and Product Family Standards specify the test levels and pass/fail performance criteria.

Test Levels

Power Frequency Magnetic Field testing is required for products that could be affected by magnetic fields, including CRTs and Hall Effect Sensors and is bly recommended for all products.

Standard	Applicability	Test Voltage
EN 50082-1	Generic Immunity - Residential, Commercial and Light Industrial	N/A
EN 50082-1 Draft	Generic Immunity - Residential, Commercial and Light Industrial	3A/m
EN 50082-2	Generic Immunity - Industrial Environment	30A/m
EN 50082-2Draft	Generic Immunity - Industrial Environment	30A/m
EN 55104	Immunity for Household Appliances, Tools and Similar Apparatus	N/A

Test Set-Up

Test Setup

Floor Test Setup

Coupling Methods

An Induction Coil having standard dimensions of 1 meter per side for a rectangular coil, or 1 meter diameter for a circular coil, is to be used for testing small equipment. For large equipment, larger dimensions may be used; however, the coil shall be able to envelop the EUT and the coil dimensions must give a minimum distance of coil conductors to EUT walls equal to 1/3 of the dimension of the EUT being tested.

Waveforms

Waveform

Waveform Verification

IEC 61000-4-8 requires that the simulator output and magnetic field be verified periodically. Any oscilloscope is capable of verifying the power frequency AC current to the coil. Monitoring the actual field requires an AC field probe and monitor.

Waveform Verification

Test Execution

According to IEC 61000-4-8, tests must be performed in compliance with the manufacturer's test plan, which shall specify:
• How the test is carried out
• Verification of the laboratory reference conditions
• Preliminary verification of the correct operation of the EUT
• An evaluation of the test results

EUT Performance Criteria

For Power Frequency Magnetic Field tests, the Generic Immunity Standards require that the product continue to operate as intended during the test, however, CRT interference is allowed above 1A/m in the residential, commercial and light industrial draft standard, and above 3A/m in the industrial standard. No degradation or loss of function is allowed below a performance level specified by the manufacturer. The performance level may be replaced by a permissible loss of performance. Refer to the tables located in the Generic, Product and Product Family Standards for specific Performance Criteria. The product cannot become unsafe under any conditions.

Power Frequency Magnetic Field Simulators

Power Frequency Magnetic Field Simulators and standard coils meet all the minimum requirements for performing tests to >3A/m in compliance with the applicable Generic and Product Family Standards.