IEC 61000-4-8 pdf download Electromagnetic compatibility (EMC) – Part 4-8: Testing and measurement techniques – Power frequency magnetic field immunity test
3.8 decoupling network, back filter electrical circuit intended to avoid reciprocal influence with other equipment not submitted to the magnetic field immunity test 3
The magnetic fields to which equipment is subjected may influence the reliable operation of equipment and systems. The following tests are intended to demonstrate the immunity of equipment when subjected to power frequency magnetic fields related to the specific location and installation condition of the equipment (e.g. proximity of equipment to the disturbance source).
The power frequency magnetic field is generated by power frequency current in conductors or, more seldom, from other devices (e.g. Ieakage of transformers) in the proximity of equipment. As for the influence of nearby conductors, one should differentiate between:
– the current under normal operating conditions, which produces a steady magnetic field, with a comparatively small magnitude;
– the current under fault conditions which can produce comparatively high magnetic fields but of short duration, until the protection devices operate (a few milliseconds with fuses, a few seconds for protection relays).
The test with a steady magnetic field may apply to all types of equipment intended for public or industrial low voltage distribution networks or for electrical plants. The test with a short duration magnetic field related to fault conditions, requires test levels that differ from those for steady-state conditions; the highest values apply mainly to equipment to be installed in exposed places of electrical plants.
The test field waveform is that of power frequency. In many cases (household areas, sub-stations and power plant under normal conditions), the magnetic field produced by harmonics is negligible.
5 Test levels
The preferential range of test levels, respectively for continuous and short duration application of the magnetic field, applicable to distribution networks at 50 Hz and 60 Hz, is given in Table 1 and Table 2. The magnetic field strength is expressed in A/m; 1 A/m corresponds to a free space induction magnetic flux density of 1 ,26 μT.
nformation on the selection of the test levels is given in Annex C.
Information on actual levels is given in Annex D.
6 Test equipment
The test magnetic field is obtained by a current flowing in an induction inductive coil; the application of the test field to the EUT is by the immersion method.
An example of application of the immersion method is given in Figure 1 .