IEC 61000-4-5:2005 relates to the immunity requirements, test methods, and range of recommended test levels for equipment to unidirectional surges caused by overvoltages from switching and lightning transients. Several test levels are defined which relate to different environment and installation conditions. These requirements are developed for and are applicable to electrical and electronic equipment. The object of this standard is to establish a common reference for evaluating the immunity of electrical and electronic equipment when subjected to surges. The test method documented in this part of IEC 61000 describes a consistent method to assess the immunity of an equipment or system against a defined phenomenon. This standard defines:
-a range of test levels
The task of the described laboratory test is to find the reaction of the EUT under specified operational conditions, to surge voltages caused by switching and lightning effects at certain threat levels. It is not intended to test the capability of the EUT’s insulation to withstand high-voltage stress. Direct injections of lightning currents, i.e, direct lightning strikes, are not considered in this standard. It has the status of a basic EMC publication in accordance with IEC Guide 107.
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Surges occur on the AC power mains as a result of switching operations in the power grid and from nearby lightning strikes, either directly to the power distribution system or to nearby ground. Radiated coupling of surges into I/O lines generally occurs only when the lines are very long.
Electronic products are tested for Surge immunity to insure their continued reliable operation if subjected to realistic levels of surge voltages. The European Union’s EMC Directive currently mandates Surge testing for some products; however, it is expected that virtually all electrical and electronic products will have to be tested for Surge immunity in the near future as a condition for obtaining the CE Mark before shipping products to a member state of the European Union.
Generic Immunity, Product and Product Family Standards require Surge tests be performed in accordance with Basic EMC Standards: IEC 801-5, IEC 61000-4-5 or EN 61000-4-5. Thermo 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.
Basic EMC Standard
The Basic EMC Standard for Surge defines the methods of generating consistently reproducible surge voltages for test purposes. They specify generator and coupler/decoupler design and performance in sufficient detail to produce correlatable results between test sites. While the Basic EMC Standard specifies how to perform Surge testing, the Generic, Product and Product Family Standards specify the test levels and pass/fail performance criteria.
|Standard||Applicability||Common Mode||Differential Mode|
|EN 50082-1||Generic Immunity – Residential, Commercial and Light Industrial||N/A||N/A|
|Generic Immunity – Residential, Commercial and Light Industrial||2kV||1kV|
|EN 50082-2||Generic Immunity – Industrial Environment||N/A||N/A|
|EN 50082-2Draft||Generic Immunity – Industrial Environment||4kV||2kV|
|EN 55104||Immunity for Household Appliances, Tools and Similar Apparatus||2kV||1kV|
When performing Surge tests, safety is a primary concern. Surge voltages and currents must be contained to insure they will not appear where they can cause damage to other instruments in the test area. The test pulses used for Surge testing are of sufficient energy to cause components to fragment under fault conditions and become hazardous to personnel in unprotected environments.
Capacitive Coupling via 9µF (Line to earth) or 18µF (line to line) capacitors is required for coupling surges to AC or DC power mains. These coupling capacitors are typically included as part of a Coupler/Decoupler (C/D) in commercially available Surge simulators. The C/D provides both coupling to the EUT power mains and a decoupler to prevent the surge from appearing on the ac mains connected to other equipment in the lab.
Capacitive Coupling via .5µF capacitors, as well as via alternative devices such as surge arrestors, are used to couple surges onto data, I/O and telecommunication lines. Surge arrestors are the preferred coupler device due to the undesirable loading effects of capacitors particularly at frequencies greater than a few kilohertz. A decoupler is included to prevent the surge from appearing at, and potentially damaging, the auxiliary equipment.
|Open Circuit Voltage 1.2 x 50 Front Time: TF = 1.67 x TRF = 1.2µsec ± 30% Duration: TD = Virtual Start to 50% = 50µsec ±20%|
|Short Circuit Current 8 x 20 Front Time: TF = 1.25 x TRF = 8µsec ± 230% Duration: TD = Virtual Start to 50% = 20µsec ±20%|
IEC 61000-4-5 requires that the simulator output be verified periodically. High voltage differential surge probes are required for verifying the open-circuit voltage, and a suitable current transformer (Pearson Model 110 or equivalent) is required for verification of the short-circuit current. A digital or storage oscilloscope with 100MHz bandwidth is sufficient for measuring the surge voltage and current waveforms and peaks.
According to IEC 61000-4-5, testing must be carried out according to the manufacturer’s test plan, which shall specify:
• Generator & other equipment
• Generator Source Impedance
• Repetition rate (one per minute maximum)
• Sequence of application of the surge
• Installation conditions
• Operating conditions of EUT
• Number of tests (at least five positive and five negative at each point)
• Test levels
• Inputs/outputs tested
• Phase angle of coupling to ac mains
• Internal or external trigger