Low voltage directive test

I. Introduction

This article will introduce the newer version of EUNEX's Low Voltage Directive and explain how to meet the requirements of the new directive. The focus will be on the requirements of CE technical documents containing test reports to assist manufacturers in responding to the LVD Directive. This article briefly states the general requirements of the instruction, and then focuses on the test requirements, and provides some examples to illustrate how to meet the related issues of LVD testing.

2. the scope of application of LVD

LVD is applicable to all motor products whose functions and voltage ranges are AC 50~1000V and DC 75~1500V. This definition refers to the scope of application of the directive, not the limit of application of the directive (for example, in a computer that uses 230V AC, DC The danger caused by the 12V circuit is also regulated by LVD).

LVD applies to products provided to consumers and industrial use. If it is industrial equipment, the directive also covers the products used by the manufacturer (for example: test equipment).

3. the requirements of CE technical documents

The CE system of LVD is similar to the EMC directive. All products within the scope of application must have the CE mark, and must have a declaration of conformity signed by the manufacturer's representative or importer.

A simple self-declaration is not enough to confirm that the product is safe ("safety" is defined as not causing deaths, injuries, and financial damage to personnel or livestock). For this reason, LVD's declaration needs to be supported by technical documentation.

The technical certification documents must include:

1. General description of machine equipment;

2. Conceptual design and manufacturing drawings;

3. Understand the descriptions and explanations necessary for these drawings;

4. List all or part of the applicable standards, and describe the countermeasures taken to meet the directive's security viewpoint;

5. The calculation result of the design and the inspection of the execution process;

6. Test report;

The manufacturer must use all necessary methods to ensure that the manufacturing process complies with the technical documents. The content of the file should clearly prove that the product is safe from the design point of view, and it can be confirmed that it is consistent throughout the manufacturing process.

A better way to establish a safety design is to first express compliance with the listed harmonization standards, and use test reports as evidence. The harmonized standards are regularly published in the Official Journal of EC (Official Journal). The use of recognized documents (such as EN specifications) can confirm that the person preparing the file considers the better information in their industry, not just their own experience. In any case, this announcement must consider the necessary safety regulations of LVD, which may exceed the requirements of harmonized standards. Generally speaking, if the product is clearly within the scope of an EN standard, then this EN standard is sufficient.

In order to ensure the continuity of compliance, the manufacturing quality system must have corresponding parameters relative to the measurable safety. At the beginning, the offline test (including grounding continuity, electrical insulation strength, and insulation resistance) of each sample before shipment. Secondly, it is necessary to be able to collect the key related to product safety from the test results. Components and materials (critical components and materials) (such as fuses, isolation transformers, flammable plastics), testing according to EN standards can identify critical components.

4. the safety test

According to a recognized specification to test whether it meets the key factors of the technical requirements of the directive, the test can be carried out by the manufacturer or a person deemed capable by the manufacturer (that is, a third-party organization performs the test or acts as a consultant).

The choice of testing in the factory or outside the factory is usually based on the manufacturer's conditions and wishes, and sometimes the buyer's requirements. In any case, the more important factor is actually the reliability of the final results. The person signing the statement should know that these test results are the basis for legal defense, but they must be correct and reproducible. If the results are measured by uncalibrated instruments or inexperienced personnel, these requirements may not be met.

For many people, their product testing experience only comes from EMC-related directives. The LVD directive test is a bit different. Simply put, EMC testing is a measurement of a defined method and limit value, while LVD Some of the tests are data collection to support a generally more subjective judgment. LVD test standards are very complicated, and the required explanations and test results required to draw conclusions are usually very thick documents.

5. the principle of safety

For electrical products, most of the LVD EN standards follow the same basic safety principles. The test is to ensure safe operation under normal execution and error conditions. These may include the influence of operators, bystanders and service personnel. It depends on the environment and specifications. In this way, all operations are predictable and reasonable. Modes and environmental conditions during operation are all considered. It is worth noting that accidental exposure to dangerous situations should be covered, while suicidal or casual behaviors are not included.

The key factors of product safety are:

1. Proper isolation system and insulation barriers are used to protect against the danger of electric shock;

2. Minimize the risk of fire, and use low-flammable components and fireproof materials to protect against the risk of fire;

2. Appropriate supervision to protect against mechanical hazards;

4. Through supervision and enclosure, to protect and prevent the equipment from leaking radioactivity and the same danger (such as X-ray, microwave);

5. Use enclosure, chemical or gas sealing to protect against chemical hazards;

6. Use barriers and protective components to protect against energy hazards (high current);

6. normal operating state

When designing a product, a combination of some components is often used to produce new functions. These components are connected and placed in an enclosure to form a relatively

For the final product, to ensure the safety of these finished products under normal operation, the ratings of components and materials and any existing document safety approvals must be considered. The previous test or approval certificate must be compiled in the test report as the content or reference of the technical file.

All documents must be tested in this new enclosed environment. If possible, increase the surrounding temperature. For example, the test should cover temperature measurement and leakage current measurement. Additional considerations must be given to the materials used in the components and For electrical isolation or fire protection, environmental testing (eg, vibration or waterproof (IP) testing) may also be required. Details of specific test items can be found in the applicable product standards.

7. the choice of multiple approved components

Many components claim to be accredited by EN standards. In any case, try to obtain copies of accreditation certificates, test reports or supporting documents from the manufacturer as much as possible. If an accreditation certificate from a non-EU factory inspection system is used, it must be associated with the IEC reference standard, FSC professional certification To ensure that the necessary safety requirements are met. For example, the requirements of UL and CSA may be different from those of IEC or EN.

8. Abnormal operating conditions

Most product safety standards can tolerate a single failure in any component. In this case, the device should be able to be continuously operated safely, or through the action of protective components (such as fuses, PTCs or thermal cutouts). It can be safely failed (safe-failure). The dangers caused by improper selection of protective components include fire and electric shock (safe insulation degradation due to heat).

The protective component must be able to operate correctly and protect the equipment in poor error situations. It is worth noting that some product standards require the protective component to be installed in the equipment. If it is allowed to be used for external protection, the exact model of the component And characteristics must be specified.

A fuse that protects the secondary circuit of a transformer is a good example of a protective component. If the time characteristics of the fuse are not properly checked (for example, a certified fuse may allow 1.5 or 2 times the rated current to pass, and it takes 30 minutes to pass). Action). In dangerous situations, it is normal for the transformer to burn before the fuse is activated.

A further example of thermal protection is as follows: In equipment with motor operation, carefully select thermal cutouts to prevent unnecessary tripping under peak conditions of normal use, but also in error conditions (such as : Deadlocked gear/drive or overload) provide safety protection.

9. spatial parameters

The structure of the entire device must be related to the arrangement of the components in the enclosure. Testing and spatial measurements must ensure that the close proximity of the components will not reduce safety (for example, the components should not be removed, which will cause safety obstacles. Arranged in a manner).

For users, the accessibility assessment of dangerous parts is another important factor. The product standard specifies various test rods and test needles to achieve this purpose. It is necessary to carefully check the size of the ventilation because these holes There is a risk of inadvertently contacting dangerous moving parts or electrical parts.

Safety switch or safety monitoring is the third example of space safety parameters. Special attention should be paid to various interlocking devices and their operating systems. Designers often use software logic circuit protection, but many product standards do not recognize that this method can be used. To provide comprehensive security, similarly, the monitoring system must be firmly fixed and effective in various predictable use situations. The use of interlocking or monitoring protection can be known by equipment users and service personnel.

10. Establish a set of future test methods

The di step is to select the relevant test standards, and use the aforementioned factors to make a preliminary inspection of the product. The main purpose is to establish the normal and abnormal operation modes, the basic conditions of the environment and the range of components within the structure.

This method allows you to establish a complete test plan and test priorities. In this way, it is a good point to define the EMC compliance requirements of the structure and components, and to identify potential conflicts when any problems occur during the test.

Keeping in mind the complexity of many product ranges, it is worthwhile to start this inspection program as early as possible. If you choose a third party to perform the test, you must keep test records to ensure that the schedule is in line, and then you must be able to determine the conclusion of the test plan. , Can be applied to your manufacturing quality system.

LVD compliance testing is not a simple process. Product standards have been developed for many years, and there are many types. Whether manufacturers can fully manage their sisters, at present, regardless of whether the manufacturer has obtained or has not yet obtained the LVD Directive approval, it is To ensure the safety of the product, it should be worth the investment of time to ensure that the product meets the requirements of the LVD directive.