Electromagnetic compatibility testing in EMC lab
EN 61000 – 4–4:2012 Electromagnetic compatibility (EMC) — Part 4 – 4: Testing and measurement techniques — Electrical fast transient/burst immunity test (IEC 61000 – 4-4:2012)
Analog: IEC 61000 – 4-4:2012 Electromagnetic compatibility (EMC) — Part 4 – 4: Testing and measurement techniques — Electrical fast transient/burst immunity test.
Replace: EN 61000 – 4-4:2004 + A1:2010 Electromagnetic compatibility (EMC) — Part 4 – 4: Testing and measurement techniques — Electrical fast transient/burst immunity test.
New in this edition: This edition improves and clarifies EFT simulator specifications, test criteria and test setups.
Scope
International standard EN 61000 – 4-4:2012 defines immunity requirements for electrical and electronic equipment to repetitive electrical fast transients on power supply, signal, control and earth ports. This standard defines test levels, test procedures and various test setups. This standard does not define Pass/Fail criteria, therefore it must be used together with generic and specific product standards where product requirements are stated.
International standard EN 61000 – 4-4:2012 defines:
- Test voltage waveforms;
- Test levels;
- Calibration procedures;
- Verification procedures;
- Specifications for laboratory and in situ tests.
General
Inductive loads such as relays, switch contactors, or heavy-duty motors when de-energized produce bursts of narrow high– frequency transients on the power distribution system. These fast transients can also be produced when the utility provider switches in or out the power factor correction equipment. A common cause of power line transients is sparking that occurs whenever an AC power cord is plugged in, equipment is switched off, or when circuit breakers are opened or closed. The EN 61000 – 4-4:2012 specification defines the test voltage waveform that is intended to simulate the transients created by switching of inductive loads on AC power lines.
Test level
International standard EN 61000 – 4-4:2012 defines following preferred test levels for various ports:
Testing level must be selected according to generic and specific product standards. Current standard also characterises various environments and recommended test levels. For power ports immunity level is twice higher than for signal and communication ports.
Level 1: Well-protected environment
Environment is characterized as:
• suppression of EFT in the switched power supply and control circuits;
• separation between power supply lines (a.c. and d.c.) and control and measurement circuits coming from other environments belonging to higher severity levels;
• shielded power supply cables with the screens earthed at both ends on the reference ground of the installation, and power supply protection by filtering.
A server room, sensitive laboratory room may represent this environment.
Level 2: Protected environment
Environment is characterized as:
• partial suppression of EFT in the power supply and control circuits which are switched only by relays (no contactors);
• poor separation of the industrial circuits belonging to the industrial environment from other circuits associated with environments of higher severity levels;
• physical separation of unshielded power supply and control cables from signal and communication cables.
The control room in EMC laboratory may represent this environment.
Level 3: Typical industrial environment
Environment is characterized as:
• no suppression of EFT in the power supply and control circuits which are switched only by relays (no contactors);
• poor separation of the industrial circuits from other circuits associated with environments of higher severity levels;
• poor separation power supply, control and telecommunication lines;
• earth represented by conductive pipes, earth conductors in the cable trays (connected to the protective earth system) and by a ground mesh.
Industrial location with assembly lines may represent this environment.
Level 4: Severe industrial environment
Environment is characterized as:
• no suppression of EFT in the power supply and control and power circuits which are switched by relays and contactors;
• no separation of the industrial circuits belonging to the severe industrial environment from other circuits associated with environments of higher severity levels;
• no separation between power supply, control, signal and communication cables;
Power plants may represent this environment.
Application of EFT pulses
Primarily, the testing involves injection of EFT pulses into the equipment’s AC power supply lines. The EFT waveform can also be injected into the signal and control lines, and earth connections to simulate the coupling of transient noise onto these lines. The pulse waveform has a high amplitude, short rise time, high repetition rate and a low energy content. It consists of a burst of 75 pulses repeated every 300 milliseconds for a duration of 1 minute. Both positive and negative polarity EFT pulses are injected during testing.
EUT is located on non-metallic table 10cm above horizontal ground plane on insulation support. Horizontal ground plane is bonded to grounding system as well as test generator and coupling decoupling network. The equipment under test shall be arranged and connected to satisfy its functional requirements, according to the equipment installation specifications.
Direct coupling of EFT voltage on power ports, using coupling/decoupling network, is preferred. For equipment under test having a power port with no earth terminal, the test voltage is only applied to L and N lines. If a suitable coupling decoupling network is not available, one of alternative methods can be used:
• in case of common and un-symmetric modes, direct injection using the (33 ± 6,6)nF capacitors is the preferred coupling mode;
• if direct injection is not practical, the capacitive clamp shall be used.
For signal, control and telecommunication ports capacitive coupling clamp is used. For earth terminals coupling decoupling device is preffered.
Performance criterion
The tests results are classified in terms of loss of function or degradation of performance. International standard EN 61000 – 4-4:2012 does not define Pass/Fail criteria. This is defined by generic or specific product standards. EN 61000 – 4-4:2012 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.