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.
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.
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.
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.
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.
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.