Elec­tro­mag­netic com­pat­i­bil­ity test­ing in EMC lab

EN 61000–4–8:2010 Elec­tro­mag­netic com­pat­i­bil­ity (EMC) — Part 4 – 8: Test­ing and mea­sure­ment tech­niques — Power fre­quency mag­netic field immu­nity test (IEC 61000 – 4-8:2009)

Ana­log: IEC 61000 – 4-8:2009 Elec­tro­mag­netic com­pat­i­bil­ity (EMC) — Part 4 – 8: Test­ing and mea­sure­ment tech­niques — Power fre­quency mag­netic field immu­nity test

Replace: EN 61000 – 4-8:1993 + A1:2001 Elec­tro­mag­netic com­pat­i­bil­ity (EMC) — Part 4 – 8: Test­ing and mea­sure­ment tech­niques — Power fre­quency mag­netic field immu­nity test


New in this edi­tion:
• Scope is intended to cover 60Hz mag­netic fields;
• Char­ac­ter­is­tics, per­for­mance, ver­i­fi­ca­tion of test gear is revised;
• Ref­er­ence ground plane and test setup details are changed.


Scope
Inter­na­tional stan­dard EN 61000 – 4-8:2010 define mag­netic field immu­nity test­ing require­ments at power fre­quency 50Hz and 60Hz in res­i­den­tial and com­mer­cial loca­tions, near indus­trial instal­la­tions and power plants, medium volt­age and high voltage-​substation.

This stan­dard does not intend to test phe­nom­ena related to dis­tur­bance cou­pling to cables due to capac­i­tive or induc­tive cou­pling.

The aim of this stan­dard is estab­lish a com­mon and repro­ducible basis for per­for­mance test­ing of elec­tri­cal and elec­tron­i­cal equip­ment for house­hold, com­mer­cial, light indus­trial, indus­trial equip­ment when exposed to con­tin­u­ous and short term mag­netic fields at power fre­quency.


Gen­eral
Mag­netic fields gen­er­ated at power line fre­quen­cies are all around. The elec­tronic equip­ment we use is sub­jected to these fields in a vari­ety of places: res­i­den­tial and com­mer­cial loca­tions, indus­trial instal­la­tions and power plants, and medium and high volt­age sub-​stations. The source of the mag­netic fields is typ­i­cally the power line cur­rent flow­ing in con­duc­tors, or occa­sion­ally, trans­form­ers in nearby equip­ment. Under nor­mal oper­at­ing con­di­tions, power line fre­quency cur­rent flows con­tin­u­ously in con­duc­tors, pro­duc­ing con­tin­u­ous or steady power line fre­quency mag­netic fields. When some type of fault occurs, the fault con­di­tion can cause com­par­a­tively high cur­rent to flow in the con­duc­tor. This high cur­rent may exist for only a short dura­tion if a pro­tec­tion device like a fuse, cir­cuit breaker, or other pro­tec­tion cir­cuitry inter­rupts the flow. High cur­rent can also tem­porar­ily exist dur­ing ini­tial power turn-​on of some elec­tronic equip­ment. A com­par­a­tively high mag­netic field will result while the cur­rent is flow­ing, but again, for only a short dura­tion. The method for test­ing equip­ment for immu­nity to mag­netic fields is to pro­duce a con­trolled mag­netic field of known field strength by dri­ving a large coil with a test gen­er­a­tor, and plac­ing the equip­ment in the cen­ter of the coil, thereby sub­ject­ing the equip­ment to the mag­netic field.


Test lev­els
Selec­tion of a test level depends on the expected oper­at­ing envi­ron­ment of the equip­ment under test (EUT). An appro­pri­ate test level for an EUT should be cho­sen based upon the mag­netic field strengths the EUT is likely to encounter in its typ­i­cal oper­at­ing envi­ron­ment. Inter­na­tional stan­dard EN 61000 – 4-8:2010 does not define spe­cific test lev­els for spe­cific prod­ucts, they must be picked up in generic stan­dards or prod­uct stan­dards.

Con­tin­u­ous mag­netic field level

Short dura­tion mag­netic field lev­els (1s… 3s)


Inter­na­tional stan­dard EN 61000 – 4-8:2010 describes envi­ron­ments as fol­lows:
Class 1: Envi­ron­ment level where sen­si­tive device with elec­tron beam is in use.
CRT mon­i­tors, an elec­tron micro­scope etc.

Class 2: Well pro­tected envi­ron­ment.
Envi­ron­ment with­out power trans­form­ers and high volt­age buss bars.
House­hold, office, hos­pi­tal pro­tected areas.

Class 3: Pro­tected envi­ron­ment.
Envi­ron­ment where cables can leak mag­netic fields, far prox­im­ity of earth con­duc­tors of pro­tec­tion sys­tems, medium volt­age and high volt­age bus bars in hun­dreds of meters.
Com­mer­cial areas, heavy indus­trial plants, server room, con­trol rooms at sub-​stations.

Class 4: Typ­i­cal indus­trial envi­ron­ment
Envi­ron­ment where short pow­er­lines as bus-​bars are present, high power elec­tri­cal equip­ment may leak mag­netic field, close prox­im­ity of ground con­duc­tors of pro­tec­tion sys­tems, medium volt­age and high volt­age bus-​bars in few tenth of meters.
Heavy indus­trial and power plants, con­trol room of high volt­age sub­sta­tion.

Class 5: Severe indus­trial envi­ron­ment
Envi­ron­ment where con­duc­tor and cables are car­ing tenth of kA, next to ground con­duc­tors of pro­tec­tion sys­tem, in close prox­im­ity of medium and high volt­age bus-​bars, next to high power elec­tri­cal equip­ment.
Switch­yard areas of heavy indus­trial plants, medium and high volt­age power sta­tions.


Test pro­ce­dure
Con­trolled mag­netic field with known field strength is pro­duced by dri­ving a large coil with a test gen­er­a­tor Equip­ment under test is placed in the mid­dle of the coil dur­ing the test, thereby sub­ject­ing the equip­ment to the mag­netic field. Proper oper­a­tion of the equip­ment is eval­u­ated dur­ing the appli­ca­tion of the field.


Attempts should be made to fully exer­cise the EUT dur­ing test­ing, and to fully inter­ro­gate all exer­cise modes selected for sus­cep­ti­bil­ity.
The use of a spe­cial exer­cis­ing pro­gram is rec­om­mended.


Per­for­mance cri­te­rion
The tests results are clas­si­fied in terms of loss of func­tion or degra­da­tion of per­for­mance. Inter­na­tional stan­dard EN 61000 – 4-8:2010 does not define Pass/​Fail cri­te­ria. This is defined by generic or spe­cific prod­uct stan­dards. EN 61000 – 4-8:2010 defines per­for­mance cri­te­ria that can be used to eval­u­ate equip­ment under test per­for­mance.

Per­for­mance cri­te­rion A
Nor­mal per­for­mance within lim­its spec­i­fied by the man­u­fac­turer;

Per­for­mance cri­te­rion B
Tem­po­rary loss of func­tion or degra­da­tion of per­for­mance. Self-​recovery after the test, with­out oper­a­tor inter­ven­tion;

Per­for­mance cri­te­rion C
Tem­po­rary loss of func­tion or degra­da­tion of per­for­mance. Oper­a­tor inter­ven­tion needed for recov­ery after the test;

Per­for­mance cri­te­rion D
Loss of func­tion or degra­da­tion of per­for­mance which is not recov­er­able. Dam­age
of hard­ware or soft­ware, or loss of data.


The manufacturer’s spec­i­fi­ca­tion may define effects on the EUT which may be con­sid­ered insignif­i­cant, and there­fore accept­able.


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