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KeyTek
Application Note Pulse Magnetic Field Background Pulse Magnetic Fields are produced as a result of a large current impulse through a conductor. An example is lightning current flowing through a grounding conductor at a power sub-station. Pulse magnetic fields can also occur in heavy industrial areas where very large current impulses are used in a manufacturing process. Electronic products are tested for immunity pulse magnetic fields to insure their continued reliable operation when placed in service in a very harsh environment. Although most electrical and electronic products will not have to be tested for pulse magnetic field immunity, the European Union's EMC Directive may mandate this testing as a condition for obtaining the CE Mark under special circumstances and for specific products before shipping to a member state of the European Union. Applicable Standards Although not currently required by Generic Immunity, Product specific, or Product Family Standards, future standards may require Pulse Magnetic Field tests be performed in accordance with Basic EMC Standards: IEC 61000-4-9 and EN 61000-4-9. KeyTek's Application Note, "EMC Standards Overview," provides an overview of European Standards for electromagnetic compatibility, describes how the Standards relate to one another, and lists sources for procuring copyrighted documents.1 IEC 61000-4-9 and EN 61000-4-9 are virtually identical standards. Basic EMC Standard The Basic EMC Standard for Pulse Magnetic Field defines methods of generating consistently reproducible current impulses for test purposes. Field amplitudes required by these standards range from 100 - 1000 Amps per meter. Although applicable only to apparatus containing devices susceptible to magnetic fields, testing may be required to make that determination. Test Levels
Test Set-Up ![](pdf/app_notes/photo/pufm_1.gif") ![](pdf/app_notes/photo/pufm_2.gif") Coupling Methods An Induction Coil having a standard dimension 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. This coil has a test volume of 0.6m x 0.6m x 0.5m (h). For floor standing equipment, larger dimensions can 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. Waveform Verification Basic test standards require that the simulator output be verified periodically. In the case of the Pulse Magnetic Field, verification is accomplished by verifying the amplitude of the 8/20µs current pulse driving the coil. An appropriate current transformer (Pearson Model 110 or equivalent) and an oscilloscope with a bandwidth of >100MHz capable of displaying a single pulse are required. ![](pdf/app_notes/photo/pufm_3.gif")
Test Execution According to IEC 61000-4-9, tests must be performed in compliance with the manufacturer's test plan, which shall specify: . How the test is performed . Verification of the laboratory reference conditions . Preliminary verification of the correct operation of the EUT . An evaluation of the test results Test Applicability According to Annex A of IEC 61000-4-9, test levels shall be selected in accordance with the most realistic installation and environmental conditions. Tests are recommended for equipment operating in areas characterized by proximity of conductors of lightning protection systems and or structures, or the proximity of conductors, bus-bars or medium to high voltage lines carrying tens of kA. Pulse Magnetic Field Simulators Pulse Magnetic Field Simulators and standard coils provided by KeyTekmeet the pulse waveform and amplitude requirements for testing to >1000A/m in accordance with IEC 61000-4-9. Consult KeyTek for larger coils used for testing floor standing equipment. Contact KeyTek for details. |
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