European Union'S Latest Version Of Low Voltage Instruction Test

I. Preface

This article will introduce the latest version of the European Union's low voltage directive and explain how to meet the requirements of the new directive. The emphasis will be placed on the requirements of the CE technical document containing the test report to assist manufacturers in responding to LVD instructions.

This article briefly describes the general requirements of instructions, and then focuses on testing requirements, and provides some examples to illustrate how to meet the relevant problems of LVD testing.

Two. Scope of application of LVD

LVD is applicable to all motor products whose functions range from AC 50~1000V to DC 75~1500V. This definition refers to the scope of application of instructions, rather than the applicable restrictions of instructions (for example, in the use of AC 230V computers, the hazards caused by DC 12V circuits are also regulated by LVD).

LVD is suitable for products provided to consumers and industries. If it is industrial equipment, the instruction also covers the products used by manufacturers themselves (e.g. test equipment).

Three. Requirements for CE technical documents

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

A simple self declaration is not enough to make sure that the product is safe. (safety is defined as causing no casualties or financial damage to personnel or livestock). For this reason, the statement of LVD needs to be supported by technical documentation.

Technical documentation should include:

General description of 1. machine equipment

2. conceptual design and manufacturing drawings

3. understand the description and description of these drawings.

4. list all or part of the applicable standards and describe the strategies adopted to meet the directive safety view.

5. design results, inspection of execution process.

6. test report

The manufacturer shall use all necessary methods to ensure that the manufacturing process is in conformity with the technical documentation. The contents of the archives shall clearly demonstrate that the product is safe in design and can be determined consistently in the manufacturing process.

A better way to establish safety design is to represent the harmonized standards listed first and take test reports as evidence.

The harmonization standard will be published regularly in the EC Official Journal.

Using approved documents, such as the EN specification, can determine that the person who prepares the file considers the best information in his industry, not just his own experience.

In any case, this declaration must consider the necessary safety specifications of LVD, which may exceed the requirements of harmonized standards.

In general, if the product is clearly within the specification of a EN standard, the EN standard is enough.

In order to ensure consistency, the manufacturing quality system has corresponding parameters relative to the evaluation safety.

First, the offline tests (including grounding continuity, electrical insulation strength, insulation resistance) of each sample before shipment are carried out. Secondly, the key components and materials (critical components and materials), such as fuse, isolating pformer and combustible plastic, which are related to product safety, can be collected from the test results, and the key components can be identified by testing according to the EN standard.

Four. Safety testing

Based on a recognized specification, whether the test meets the key requirements of the technical requirements of the instruction, the test can be carried out by the manufacturer or manufacturer who considers the competent person (that is to say, a test run by the third party or a consultant).

It is usually tested according to the manufacturer's conditions and wishes, and sometimes the buyer's request.

In any case, in fact, the most important factor is the reliability of the final result. Those who sign the declaration should know that these test results are the basis for legal defense, but must be correct and reproducible.

If the result is not measured by the uncalibrated instrument or the experienced personnel, it may not be able to meet these requirements.

For many people, their experience in testing products only comes from EMC related instructions, and LVD instructions are somewhat different. Simply speaking, EMC tests are targeted at well-defined methods, limiting the measurement of values, while LVD tests are collections of data to support a more subjective judgment. The LVD test standard is very complex, and the test results required for instructions and conclusions are usually very thick.

Five, the principle of safety

For electrical appliances, most 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, spectators and service personnel, depending on the environment and specifications. In this way, all predictable and reasonable mode of operation and environmental conditions in operation are taken into consideration. It is worth noting that accidental exposure to dangerous situations should be covered, while suicide or casual behavior is not in the range.

The key factors of product safety are:

1., through proper isolation system and insulation barrier, to protect against the danger of electric shock.

2. minimize the risk of fire, use low combustible components and fireproof materials to protect against fire hazards.

3. proper supervision to protect against mechanical hazards.

4. by supervision and enclosure, to prevent the leakage of radioactivity and the same danger (such as X light, microwave).

5. enclosure, chemical or gas seals to protect against chemical hazards.

6. barrier and protective components to protect against exposure to energy hazards (high current).

Six. Normal operation state

When designing products, they often use new combinations of components to generate new functions. These components are linked together in a enclosure to form the final product. In order to ensure the safety of these finished products under normal operation, the rating of components and materials and any existing document safety approval must be taken into consideration.

A certificate previously tested or approved must be arranged in the test report as the content or reference of the technical document.

All documents must be tested in this new enclosure environment. If possible, the ambient temperature should be increased. For example, the test should cover temperature measurement and leakage current test. Additional consideration should be given to the materials used in the components and electrical isolation or fire protection. Environmental tests may also be required (for example, vibration or waterproofing (IP) test).

Details of specific test items can be found in applicable product standards.

Seven. The choice of multiple authorized components.

Many components are claimed to be approved by the EN standard. In any case, it is necessary to obtain the photocopy of the certificate of approval, test report or certification document to the manufacturer. If the certificate of non EU certification system is used, it must be determined to be related to the IEC reference standard so as to ascertain the necessary safety requirements.

For example, the requirements of UL and CSA may be different from those of IEC or EN.

Eight. Abnormal operation state

Most product safety standards allow for a single failure within any component. In such cases, the device should be continuously operated safely or be able to fail safely through the action of protective components (such as fuse, PTC or thermal Interrupter) (safe-failure). The risk posed by improper selection of protection components includes fire and electric shock (due to thermal insulation deterioration caused by heat).

Protection components must be able to act correctly and protect devices in the worst case of error. It is worth noting that some product standards require protection components to be installed in the equipment. If permitted to use external protection, the exact models and characteristics of the components must be specified.

The protection of the fuse in the two circuit of the pformer is a good example of a protective component. If there is no proper checking of the time characteristics of the fuse (for example, a recognized fuse may allow 1.5 or 2 times the rated current to pass, and it takes 30 minutes to act), in case of danger, the pformer will burn normally before the fuse is in motion.

Further examples of thermal protection are as follows: in the equipment with motor operation, carefully choose the thermal effect cut-off device to prevent unnecessary tripping in the peak condition of normal use, and also provide security protection in the wrong condition (such as deadlocked gear / drive or overload).

Nine. Spatial parameters

The structure of the whole equipment must be related to the arrangement of the components in the enclosure. Testing and measuring in space should make sure that the close proximity of the components will not reduce the safety (for example, the components should not be arranged in a way of safety obstruction if they are removed).

For users, accessibility assessment of dangerous parts is another important factor. Product standards set out a variety of test rods and test needles to achieve this purpose. It is necessary to carefully check the size of ventilation and fear, because these holes are inadvertently exposed to dangerous mobile parts or hazardous parts.

Safety switches or safety monitoring are third examples of space safety parameters. Special attention is paid to various interlocking devices and their operating systems. Designers often use the protection of software logic circuits, but many product standards do not consider this way to provide comprehensive safety. Similarly, monitoring systems must be firmly secured and are effective in all kinds of predictable situations. The use of interlocking or monitoring protection can be known by equipment users and service personnel.

Ten. Set up a set of future testing methods.

The first step is to select the relevant test standards and make a preliminary inspection of the products with the above mentioned factors. The main purpose is to establish normal and abnormal mode of operation, the basic conditions of the environment and the scope of components in the structure.

This approach enables you to establish complete test plans and test priorities.

It is a good idea to define the EMC of the structure and components to meet the requirements, and to identify potential conflicts in the course of testing.

Keep in mind the complexity of many product ranges, it is worthwhile to start this inspection process as early as possible. If you choose third party organizations to perform tests, you must retain test records to ensure that the timing is consistent, and finally you can determine the conclusion of the test plan and apply it to your manufacturing quality system.

LVD testing is not a simple process. The product standard has been developed for many years, and there are many kinds of manufacturers. Whether the manufacturer has obtained or has not yet obtained the LVD directive approval, in order to ensure the safety of the product, it should be worth investing time to ensure that the product can meet the requirements of the LVD directive.