untitled NORME INTERNATIONALE CEI IEC INTERNATIONAL STANDARD 60068 2 1 Sixième édition Sixth edition 2007 03 Essais d’environnement – Partie 2 1 Essais – Essai A Froid Environmental testing – Part 2 1[.]
Généralités
A specimen is deemed to dissipate energy when the temperature at its hottest point, measured under calm air conditions (i.e., with low air circulation speed), exceeds the surrounding atmospheric temperature by more than 5 K after thermal stability has been reached (refer to section 4.8 of IEC 60068-1) If the specific requirements dictate a storage or transport test or do not specify dissipation conditions during testing, the cold test Ab will be applied.
Vérification de la haute ou faible vitesse de l’air dans la chambre d’essai
Under normal atmospheric conditions for measurements and testing (refer to IEC 60068-1), with an air velocity of less than 0.2 m/s achieved without induced airflow, the specimen must be powered or subjected electrically to dissipation conditions as specified for the low temperature at which the test is conducted.
Once the thermal stability of the specimen is achieved, the temperature at several representative points around or above the specimen must be measured using appropriate control equipment The resulting temperature increase at each point should be recorded.
IEC 60068-3-5, Environmental testing – Part 3-5: Supporting documentation and guidance – Confirmation of the performance of temperature chambers
IEC 60068-3-7, Environmental testing – Part 3-7: Supporting documentation and guidance – Measurements in temperature chambers for tests A and B (with load)
IEC 60068-5-2, Environmental testing – Part 5-2: Guide to drafting of test methods – Terms and definitions
IEC 60721 (all parts), Classification of environmental conditions
For the purposes of this document, the definitions given in IEC 60068-5-2, as well as the following definitions, apply
Maintaining low air velocity in the working space is crucial for effective conditioning airflow The airflow should be sufficient to uphold optimal conditions while ensuring that the temperature at any point on the test specimen does not decrease by more than 5 K due to air circulation Ideally, this air velocity should not exceed 0.5 m/s.
High air velocity in the working space is crucial for maintaining optimal conditions, as it effectively reduces the temperature at any point on the test specimen by more than 5 K due to the influence of air circulation.
4 Application of tests for non heat-dissipating specimens versus tests for heat-dissipating specimens
A specimen is classified as heat-dissipating if its hottest surface point, measured in free air conditions, exceeds the ambient temperature by more than 5 K after achieving temperature stability, as outlined in IEC 60068-1 (section 4.8) In cases where the specification requires a storage or transportation test, or does not define an applied load, the Cold Test Ab will be implemented.
4.2 Ascertaining high or low air velocity in the test chamber
Under standard atmospheric conditions for testing (refer to IEC 60068-1), with an air velocity of less than 0.2 m/s and without induced air movement, the specimen must be powered on or electrically loaded according to the specified low temperature for the test.
When temperature stability of the specimen has been reached, the temperature of a number
The test chamber is activated, and once the temperature stabilizes, the temperatures of representative points must be re-measured If the temperatures differ by more than 5 K (or a specified value) from those measured without air flow, this discrepancy must be recorded in the test report, indicating that the test chamber has high-speed air circulation The specimen is then halted, and the dissipation conditions are removed.
Pour les spécimens ne dissipant pas d’énergie
In the slow temperature variation test, the specimen is placed in a chamber initially set to the laboratory temperature The temperature in the chamber is then gradually lowered to prevent destructive effects on the specimen caused by rapid temperature changes A high air velocity is recommended, as it will decrease the time required for temperature stabilization.
Essai de spécimens dissipant de l’énergie
The Ad and Ae tests outline the procedures for testing energy-dissipating specimens under low air velocity conditions This approach facilitates the development of localized hot spots within the specimen, similar to those that may occur in installed applications.
Surveillance de la température
The air temperature in the test chamber must be measured using temperature sensors positioned at a distance from the specimen to minimize the effects of heat dissipation It is advisable to take appropriate precautions to prevent heat radiation from influencing these measurements For further details, refer to IEC 60068-3-5.
Emballage
For storage and transport testing, equipment can be evaluated with its packaging intact However, since these tests are conducted under continuous conditions, the equipment will eventually stabilize at the temperature of the test chamber The packaging should be removed unless specific requirements dictate that it must remain or if heating elements are incorporated within it.
Représentations par diagrammes
Pour faciliter le choix de la méthode d’essai, une représentation des diverses procédures par un diagramme est donnée à la Figure 1
Once the chamber is activated and temperature stability is reached, the temperatures at key points are measured again If these temperatures differ from the initial measurements taken without airflow by more than 5 K (or a specified value), this discrepancy will be documented in the test report, indicating that the test chamber exhibits high velocity circulation Subsequently, the specimen is turned off, and any loading conditions are removed.
In Test Ab, the specimen is placed in a test chamber initially set to laboratory temperature The chamber's temperature is then gradually lowered to prevent any harmful effects on the specimen To expedite temperature stabilization, a high air velocity is recommended.
4.4 Testing of heat-dissipating specimens
Tests Ad and Ae outline methods for evaluating heat-dissipating specimens under conditions of low air velocity circulation This approach facilitates the formation of localized hot spots within the specimen, mirroring the conditions found in actual installed applications.
Air temperature in the chamber must be measured using sensors positioned far enough from the specimen to minimize the impact of heat dissipation It is essential to implement appropriate measures to prevent heat radiation from influencing these temperature readings For additional details, refer to IEC 60068-3-5.
For storage and transportation tests, equipment is often evaluated with its packaging intact However, since these tests are conducted under steady-state conditions, the equipment will eventually reach equilibrium with the chamber temperature Packaging should be removed unless specified otherwise or if the package includes heating elements.
To facilitate the choice of test method, a diagrammatic representation of the various procedures is given in Figure 1
Fournie durant la période de conditionnement?
Figure 1 – Diagramme complet des essais A: Froid
Généralités
The Ab, Ad, and Ae tests are similar, with differences noted in sections 5.2.2, 5.3.2, and 5.4.2 All other parts of the test remain consistent from Article 6 onwards The temperature variation in the test chamber must not exceed 1 K per minute, averaged over a period not exceeding 5 minutes The specific requirements should outline the operation of the specimen being tested.
Des précautions doivent être prises pour que tout matériel de refroidissement du spécimen soit en accord avec les prescriptions de la spécification particulière.
Essai Ab: Froid pour spécimens ne dissipant pas d’énergie avec variation
Objet
Cette procédure s’applique aux spécimens qui sont soumis à des conditions de basse température pendant une durée suffisante pour que le spécimen atteigne la stabilité thermique
Figure 1 – Block diagram tests A: Cold
Tests Ab, Ad, and Ae share similarities, with differences highlighted in sections 5.2.2, 5.3.2, and 5.4.2 All other aspects of the tests remain consistent, beginning from Clause 6 It is essential that the temperature change within the chamber does not exceed 1 K per minute, averaged over a maximum period.
5 min The relevant specification shall define the functioning of the specimen under test
Care shall be taken to see that any cooling devices of the specimen are in accordance with the requirement in the relevant specification
5.2 Test Ab: Cold for non heat-dissipating specimens with gradual change of temperature 5.2.1 Object
This procedure is intended for non heat-dissipating specimens which are subjected to a lower temperature for a time long enough for the specimen to achieve temperature stability.
Description générale
Le spécimen est introduit dans la chambre qui est à la température ambiante du laboratoire
The chamber temperature is adjusted to the severity level specified in the particular specification Once thermal stability of the specimen is achieved, it is maintained under these conditions for the specified duration For specimens that require operation, even if they do not meet energy dissipation requirements, they must be powered on, and functional testing is conducted as needed An additional stabilization period may be necessary, during which the specimen should be exposed to low-temperature conditions for the duration outlined in the particular specification.
Les spécimens en essai sont normalement placés dans des conditions de non- fonctionnement
Une circulation d’air à haute vitesse est normalement utilisée pour cet essai.
Essai Ad: Froid pour spécimens dissipant de l’énergie avec variation lente
Objet
Cette procédure s’applique aux spécimens dissipant de l’énergie qui sont soumis à des conditions de basse température pendant une durée suffisante pour que le spécimen atteigne la stabilité thermique.
Description générale
Le spécimen est introduit dans la chambre qui est à la température ambiante du laboratoire
If necessary, a test is conducted to assess whether the test chamber meets the low air speed requirements The temperature in the chamber is then adjusted to the level specified according to the severity indicated in the specific guidelines.
Once the thermal stability of the specimen is achieved, it is activated and, after stabilization, subjected to the specified conditions for the designated duration The specimen must remain within the operational conditions according to its operating cycle and dissipation conditions (if applicable) as outlined in the specific requirements.
Une circulation d’air à faible vitesse est normalement utilisée pour cet essai.
Essai Ae: Froid pour spécimens dissipant de l’énergie avec variation lente
Objet
This procedure applies to energy-dissipating specimens subjected to low-temperature conditions for a sufficient duration to achieve thermal stability, and which are operated during the testing period.
Description générale
Le spécimen est introduit dans la chambre qui est à la température ambiante du laboratoire
If necessary, a test is conducted to determine if the test chamber meets the requirements for low air speed The specimen is then energized, and a functional test is performed as needed The temperature in the chamber is subsequently adjusted.
The specimen is placed in a chamber at laboratory temperature, which is then adjusted to the specified severity level Once the specimen reaches temperature stability, it is subjected to these conditions for the required duration For operational specimens, power is applied for functional testing, and additional stabilization may be needed before exposing the specimen to low temperature conditions for the specified time.
Specimens under test are normally in non-operating conditions
High air velocity circulation is normally used for this test
5.3 Test Ad: Cold for heat-dissipating specimens with gradual change of temperature that are powered after initial temperature stabilization 5.3.1 Object
This procedure is for heat-dissipating specimens which are subjected to a low temperature for a time long enough for the specimen to achieve temperature stability
The specimen is placed in a laboratory-temperature chamber, where a test may be conducted to ensure low air velocity requirements are met Subsequently, the temperature is adjusted to align with the specified severity level outlined in the relevant standards.
Once the test specimen achieves temperature stability, it is powered on and allowed to stabilize again before being subjected to the specified conditions for the designated duration The specimen must operate according to the duty cycle and maintain the loading condition, if applicable, as outlined in the relevant specifications.
Low air velocity circulation is normally used for this test
5.4 Test Ae: Cold for heat-dissipating specimens with gradual change of temperature that are required to be powered throughout the test 5.4.1 Object
This procedure is designed for heat-dissipating specimens that must be maintained at a low temperature for an extended duration to achieve thermal stability, while also requiring power throughout the testing period.
The specimen is placed in a laboratory-temperature chamber, where a test may be conducted to ensure it meets the criteria for a low air velocity chamber Following this, power is supplied to the specimen, and a functional test is carried out.
Lorsque la stabilité thermique du spécimen est atteinte, celui-ci est soumis à ces conditions pendant la durée spécifiée
Une circulation d’air à faible vitesse est normalement utilisée pour cet essai.
Recharge du spécimen
Le spécimen doit alors être mis sous tension ou soumis électriquement à des conditions de dissipation et contrôlé pour s’assurer qu’il est capable de fonctionner selon la spécification particulière
Le spécimen doit rester dans les conditions de fonctionnement selon son cycle de fonctionnement et les conditions de dissipation (si applicables) comme prescrit dans la spécification particulière
Confirmation de performance
La CEI 60068-3-5 fournit des conseils pour la confirmation de performance de température des chambres d’essais La CEI 60068-3-1 fournit des conseils généraux pour la performance des essais A et B
La chambre d’essai doit être suffisamment grande comparée à la taille et à la quantité de dissipation d’énergie de l’échantillon d’essai.
Espace de travail
Les dimensions de l’échantillon d’essai doivent être telles qu’il puisse être placé entièrement dans l’espace de travail de la chambre d’essai
The air temperature directed at the test specimen must be maintained within ± 2 K of the specified severity temperature during continuous operating conditions Additionally, the air temperature in the workspace should be measured according to section 4.5.
If the dimensions of the test chamber do not allow for the maintenance of these tolerances, the tolerance may be expanded to ±3 K down to -25 °C and to ±5 K down to -65 °C When this adjustment is made, the tolerance applied must be specified in the test report.
Radiation thermique
The specimen's ability to transfer heat through thermal radiation must be minimized This can be achieved by inspecting all heating or cooling elements of the specimen, ensuring that parts of the test chamber surfaces do not significantly differ in temperature from the air during the test.
Spécimen avec refroidissement artificiel
The specific specification must outline the characteristics of the specimen's cooling system When air is used as the coolant, it is crucial to ensure that the air is free from oil contamination and sufficiently dry to prevent mold issues.
After temperature stability of the test specimen has been reached, the specimen is exposed to these conditions for the specified duration
Low air velocity circulation is normally used for this test
The specimen shall then be switched on or electrically loaded and checked to ascertain whether it is capable of functioning in accordance with the relevant specification
The specimen shall remain in the operating condition in accordance with the duty cycle and at the loading condition (if applicable) as prescribed by the relevant specification
IEC 60068-3-5 provides guidance for the confirmation of performance of temperature test chambers IEC 60068-3-1 provides general guidance for the performance of Tests A and B
The chamber shall be large enough compared with the size and amount of heat-dissipation of the test sample
The dimensions of the test sample shall be such that it is entirely within the working space of the test chamber
The incident air temperature delivered to the test specimen must remain within ± 2 K of the specified test severity temperature during steady-state conditions Additionally, the air temperature in the working space should be measured according to section 4.5.
In cases where the chamber size makes it impractical to uphold strict tolerances, the allowable tolerance may be adjusted to ±3 K for temperatures down to –25 °C and ±5 K for temperatures down to –65 °C It is essential to specify the applied tolerance in the test report.
To minimize the specimen's heat transfer through thermal radiation, it is essential to shield any heating or cooling elements from the specimen Additionally, maintaining uniform temperature across the chamber surfaces, in line with the conditioning air, is crucial.
The specification must outline the properties of the coolant used for the specimen When using air as the coolant, it is essential to ensure that the air is free from oil contamination and sufficiently dry to prevent moisture-related issues.
Montage
It is advisable to specify the thermal condition and other relevant characteristics of the assembly and connections of the test specimen in the particular specification When the test specimen is intended for use with specific mounting equipment, that equipment should be utilized for the testing.
Sévérités
Température
Durée
When conducting endurance or reliability tests, it is essential to consider the IEC publications that provide specific recommendations regarding the duration of these tests.
Pré-conditionnement
La spécification particulière peut prescrire un pré-conditionnement.
Mesures initiales
L’état initial du spécimen doit être connu Celui-ci peut être déterminé par une inspection visuelle, et/ou par des essais fonctionnels tels que décrits dans la spécification particulière.
Conditionnement
Le spécimen doit être exposé à des conditions de basse température durant le temps précisé dans la spécification particulière
Pour des cas exceptionnels, lorsque le spécimen n’atteint pas une stabilité thermique, la durée de l’essai commence au moment ó le spécimen est en charge De tels cas sont
The relevant specifications must detail the thermal conduction and characteristics of the mounting and connections for the test specimen Testing should be conducted using the specific mounting devices intended for the test specimen's use.
The severities, determined by temperature and exposure duration, must adhere to the relevant specifications They can be selected from the values outlined in sections 6.6.1 and 6.6.2, derived from the known environment if it yields significantly different values, or obtained from other credible data sources, such as IEC 60721.
When conducting tests related to endurance or reliability, it is essential to consider the specific recommendations outlined in IEC publications regarding the duration of these tests.
The relevant specification may call for preconditioning
The initial state of the specimen shall be known This may be achieved by visual inspection, and/or functional tests as required by the relevant specification
The specimen shall be exposed to the low temperature conditions for the duration, as detailed in the relevant specification
In exceptional cases where the specimen fails to reach temperature stability, the test duration begins when the specimen is energized These situations often arise from specimens with extended duty cycles.
General
A specimen is classified as heat-dissipating if its hottest surface point, measured in free air conditions, exceeds the ambient temperature by more than 5 K after achieving temperature stability, as outlined in IEC 60068-1 (section 4.8) In cases where the specification requires a storage or transportation test, or does not define an applied load, the Cold Test Ab will be implemented.
Ascertaining high or low air velocity in the test chamber
Under standard atmospheric conditions for testing (refer to IEC 60068-1), with an air velocity of less than 0.2 m/s and without induced air movement, the specimen must be powered on or electrically loaded according to the specified low temperature for the test.
When temperature stability of the specimen has been reached, the temperature of a number
The test chamber is activated, and once the temperature stabilizes, the temperatures of representative points must be measured again If the temperatures differ by more than 5 K (or a specified value) from those measured without air flow, this discrepancy must be recorded in the test report, indicating that the test chamber has high-speed air circulation The specimen is then halted, and the dissipation conditions are removed.
4.3 Pour les spécimens ne dissipant pas d’énergie
In the slow temperature variation test, the specimen is placed in a chamber initially set to the laboratory temperature The temperature in the chamber is then gradually lowered to prevent destructive effects on the specimen caused by rapid temperature changes A high air velocity is recommended, as it will decrease the time required for temperature stabilization.
4.4 Essai de spécimens dissipant de l’énergie
The Ad and Ae tests outline the procedures for testing energy-dissipating specimens under low air velocity conditions This approach facilitates the development of localized hot spots within the specimen, similar to those that may occur in installed applications.
The air temperature in the test chamber must be measured using temperature sensors positioned at a distance from the specimen to minimize the effects of heat dissipation It is advisable to take appropriate precautions to prevent heat radiation from influencing these measurements For further details, refer to IEC 60068-3-5.
For storage and transport testing, equipment can be evaluated with its packaging intact However, since these tests are conducted under continuous conditions, the equipment will eventually stabilize at the test chamber's temperature The packaging should be removed unless specific requirements dictate that it must remain or if heating elements are incorporated within it.
Pour faciliter le choix de la méthode d’essai, une représentation des diverses procédures par un diagramme est donnée à la Figure 1
Once the chamber is activated and temperature stability is reached, the temperatures at key points are measured again If these temperatures differ from the initial measurements taken without airflow by more than 5 K (or a specified value), this discrepancy will be recorded in the test report, indicating that the test chamber exhibits high-velocity circulation Subsequently, the specimen is turned off, and all loading conditions are removed.
Non heat-dissipating specimens
In Test Ab, the specimen is placed in a test chamber initially set to laboratory temperature The chamber's temperature is then gradually lowered to prevent any harmful effects on the specimen from the temperature change To expedite temperature stabilization, a high air velocity is recommended.
Testing of heat-dissipating specimens
Tests Ad and Ae outline methods for evaluating heat-dissipating specimens under conditions of low air velocity circulation This approach facilitates the formation of localized hot spots within the specimen, mirroring the conditions found in actual installed applications.
Temperature monitoring
Air temperature in the chamber must be measured using sensors positioned far enough from the specimen to minimize the impact of heat dissipation It is essential to implement appropriate measures to prevent heat radiation from influencing these temperature readings For additional details, refer to IEC 60068-3-5.
Packaging
For storage and transportation tests, equipment is often evaluated with its packaging intact However, since these tests are conducted under steady-state conditions, the equipment will eventually reach equilibrium with the chamber temperature Packaging should be removed unless specified otherwise or if the package includes heating elements.
Diagrammatic representations
To facilitate the choice of test method, a diagrammatic representation of the various procedures is given in Figure 1
Fournie durant la période de conditionnement?
Figure 1 – Diagramme complet des essais A: Froid
The Ab, Ad, and Ae tests are similar, with differences noted in sections 5.2.2, 5.3.2, and 5.4.2 All other parts of the test remain consistent from Article 6 onwards The temperature variation in the test chamber must not exceed 1 K per minute, averaged over a period not exceeding 5 minutes The specific requirements should outline the operation of the specimen being tested.
Des précautions doivent être prises pour que tout matériel de refroidissement du spécimen soit en accord avec les prescriptions de la spécification particulière
5.2 Essai Ab: Froid pour spécimens ne dissipant pas d’énergie avec variation lente de la température 5.2.1 Objet
Cette procédure s’applique aux spécimens qui sont soumis à des conditions de basse température pendant une durée suffisante pour que le spécimen atteigne la stabilité thermique
Figure 1 – Block diagram tests A: Cold
General
Tests Ab, Ad, and Ae share similarities, with differences highlighted in sections 5.2.2, 5.3.2, and 5.4.2 All other aspects of the tests remain consistent, beginning from Clause 6 It is essential that the temperature change within the chamber does not exceed 1 K per minute, averaged over a maximum period.
5 min The relevant specification shall define the functioning of the specimen under test
Care shall be taken to see that any cooling devices of the specimen are in accordance with the requirement in the relevant specification.
Test Ab: Cold for non heat-dissipating specimens with gradual change of temperature
Object
This procedure is intended for non heat-dissipating specimens which are subjected to a lower temperature for a time long enough for the specimen to achieve temperature stability
Le spécimen est introduit dans la chambre qui est à la température ambiante du laboratoire
The chamber temperature is adjusted to the severity level specified in the particular specification Once thermal stability of the specimen is achieved, it is maintained under these conditions for the specified duration For specimens that require operation, even if they do not meet energy dissipation requirements, they must be powered on, and functional testing is conducted as needed An additional stabilization period may be necessary, during which the specimen should be exposed to low-temperature conditions for the duration outlined in the particular specification.
Les spécimens en essai sont normalement placés dans des conditions de non- fonctionnement
Une circulation d’air à haute vitesse est normalement utilisée pour cet essai
5.3 Essai Ad: Froid pour spécimens dissipant de l’énergie avec variation lente de la température lorsqu’ils sont mis en fonctionnement après une stabilisation de la température
Cette procédure s’applique aux spécimens dissipant de l’énergie qui sont soumis à des conditions de basse température pendant une durée suffisante pour que le spécimen atteigne la stabilité thermique
Le spécimen est introduit dans la chambre qui est à la température ambiante du laboratoire
If necessary, a test is conducted to assess whether the test chamber meets the low air speed requirements The temperature in the chamber is then adjusted to the value corresponding to the severity level specified in the particular specification.
Once the thermal stability of the specimen is achieved, it is activated and, after stabilization, subjected to the specified conditions for the designated duration The specimen must remain within the operational conditions according to its operating cycle and dissipation conditions (if applicable) as outlined in the specific requirements.
Une circulation d’air à faible vitesse est normalement utilisée pour cet essai
5.4 Essai Ae: Froid pour spécimens dissipant de l’énergie avec variation lente de la température qui impliquent d’être mis en fonctionnement durant l’essai 5.4.1 Objet
This procedure applies to energy-dissipating specimens subjected to low-temperature conditions for a sufficient duration to achieve thermal stability, and which are operated during the testing period.
Le spécimen est introduit dans la chambre qui est à la température ambiante du laboratoire
If necessary, a test is conducted to determine if the test chamber meets the low air speed requirements The specimen is then energized, and a functional test is performed as needed The temperature in the chamber is subsequently adjusted to the desired level.
General description
The specimen is placed in a laboratory chamber, where the temperature is adjusted to the specified severity level Once the specimen reaches temperature stability, it is subjected to these conditions for the required duration For operational specimens, power is applied for functional testing, which may require additional stabilization Finally, the specimen is exposed to low temperature conditions for the duration outlined in the relevant specifications.
Specimens under test are normally in non-operating conditions
High air velocity circulation is normally used for this test.
Test Ad: Cold for heat-dissipating specimens with gradual change of
Object
This procedure is for heat-dissipating specimens which are subjected to a low temperature for a time long enough for the specimen to achieve temperature stability.
General description
The specimen is placed in a laboratory-temperature chamber, where a test may be conducted to ensure low air velocity requirements are met Subsequently, the temperature is adjusted to align with the specified severity level outlined in the relevant standards.
Once the test specimen achieves temperature stability, it is powered on and allowed to stabilize again before being subjected to the specified conditions for the designated duration The specimen must operate according to the duty cycle and maintain the loading condition, if applicable, as outlined in the relevant specifications.
Low air velocity circulation is normally used for this test.
Test Ae: Cold for heat-dissipating specimens with gradual change of
Object
This procedure is designed for heat-dissipating specimens that must be maintained at a low temperature for an extended duration to achieve thermal stability, while also being powered during the entire testing period.
General description
The specimen is placed in a laboratory-temperature chamber, where a test may be conducted to ensure it meets the criteria for a low air velocity chamber Following this, power is supplied to the specimen, and a functional test is carried out.
Lorsque la stabilité thermique du spécimen est atteinte, celui-ci est soumis à ces conditions pendant la durée spécifiée
Une circulation d’air à faible vitesse est normalement utilisée pour cet essai
Le spécimen doit alors être mis sous tension ou soumis électriquement à des conditions de dissipation et contrôlé pour s’assurer qu’il est capable de fonctionner selon la spécification particulière
Le spécimen doit rester dans les conditions de fonctionnement selon son cycle de fonctionnement et les conditions de dissipation (si applicables) comme prescrit dans la spécification particulière
La CEI 60068-3-5 fournit des conseils pour la confirmation de performance de température des chambres d’essais La CEI 60068-3-1 fournit des conseils généraux pour la performance des essais A et B
La chambre d’essai doit être suffisamment grande comparée à la taille et à la quantité de dissipation d’énergie de l’échantillon d’essai
Les dimensions de l’échantillon d’essai doivent être telles qu’il puisse être placé entièrement dans l’espace de travail de la chambre d’essai
The air temperature directed at the test specimen must be maintained within ± 2 K of the temperature that defines the severity of the test during continuous operating conditions Additionally, the air temperature in the workspace should be measured according to section 4.5.
If the dimensions of the test chamber do not allow for the maintenance of these tolerances, the tolerance may be expanded to ±3 K down to -25 °C and to ±5 K down to -65 °C When this adjustment is made, the tolerance applied must be specified in the test report.
The specimen's ability to transfer heat through thermal radiation must be minimized This can be achieved by inspecting all heating or cooling elements of the specimen, ensuring that the surfaces of the test chamber do not significantly differ in temperature from the air during the test.
The specific specification must outline the characteristics of the specimen's cooling medium When air is used as the cooling medium, it is crucial to ensure that the air is free from oil contamination and sufficiently dry to prevent mold issues.
After temperature stability of the test specimen has been reached, the specimen is exposed to these conditions for the specified duration
Low air velocity circulation is normally used for this test.
Energizing the specimen
The specimen shall then be switched on or electrically loaded and checked to ascertain whether it is capable of functioning in accordance with the relevant specification
The specimen shall remain in the operating condition in accordance with the duty cycle and at the loading condition (if applicable) as prescribed by the relevant specification
Confirmation of performance
IEC 60068-3-5 provides guidance for the confirmation of performance of temperature test chambers IEC 60068-3-1 provides general guidance for the performance of Tests A and B
The chamber shall be large enough compared with the size and amount of heat-dissipation of the test sample.
Working space
The dimensions of the test sample shall be such that it is entirely within the working space of the test chamber
The incident air temperature delivered to the test specimen must remain within ± 2 K of the specified test severity temperature during steady-state conditions Additionally, the air temperature in the working space should be measured according to section 4.5.
In cases where the chamber size makes it impractical to maintain strict tolerances, the allowable tolerance may be adjusted to ±3 K for temperatures down to –25 °C and ±5 K for temperatures down to –65 °C It is essential to specify the adjusted tolerance in the test report.
Thermal radiation
To minimize the specimen's heat transfer through thermal radiation, it is essential to shield any heating or cooling elements from the specimen Additionally, maintaining uniform temperature across the chamber surfaces, in line with the conditioning air, is crucial.
Specimen with artificial cooling
The specification must outline the properties of the coolant used for the specimen When utilizing air as the coolant, it is essential to ensure that the air remains free from oil contamination and is sufficiently dry to prevent moisture-related issues.
It is advisable to specify the thermal condition and other relevant characteristics of the assembly and connections of the test specimen in the particular specification When the test specimen is intended for use with specific mounting equipment, that equipment should be utilized for the testing.
The severities, defined by temperature and duration of exposure, must be specified in the particular specification They should be selected from those indicated in sections 6.6.1 and 6.6.2, derived from the known environment if it provides significantly different values, or obtained from other recognized sources based on relevant data, such as IEC 60721.
When conducting endurance or reliability tests, it is essential to consider the IEC publications that provide specific recommendations regarding the duration of these tests.
La spécification particulière peut prescrire un pré-conditionnement
L’état initial du spécimen doit être connu Celui-ci peut être déterminé par une inspection visuelle, et/ou par des essais fonctionnels tels que décrits dans la spécification particulière
Le spécimen doit être exposé à des conditions de basse température durant le temps précisé dans la spécification particulière
Pour des cas exceptionnels, lorsque le spécimen n’atteint pas une stabilité thermique, la durée de l’essai commence au moment ó le spécimen est en charge De tels cas sont
Mounting
The specifications must detail the thermal conduction and other essential characteristics of the mounting and connections for the test specimen If the test specimen is designed for use with particular mounting devices, those devices should be utilized during testing.
Severities
Temperature
Duration
When conducting tests related to endurance or reliability, it is essential to refer to IEC publications that provide specific recommendations regarding the duration of these tests.
Preconditioning
The relevant specification may call for preconditioning.
Initial measurements
The initial state of the specimen shall be known This may be achieved by visual inspection, and/or functional tests as required by the relevant specification
The specimen shall be exposed to the low temperature conditions for the duration, as detailed in the relevant specification
In exceptional cases where the specimen fails to achieve temperature stability, the test duration begins when the specimen is energized These situations often arise from specimens with long duty cycles.
The specific specification may outline conditions for dissipation and/or measurements during or at the end of the test while the specimen remains in the chamber If such measurements are necessary, the specification must clearly define them and specify when they should be conducted The specimen must not be removed from the chamber until all measurements are completed.
If one wishes to assess the performance of the specimen before the end of the prescribed duration, it is essential to test an additional batch of specimens for each specified duration It is important that the recovery and final measurements are conducted separately for each batch.
If the specimen remains operational or is subjected to dissipation conditions during the test, it must be powered down or removed from dissipation conditions before the temperature reaches the exceptional test temperature Ae, at which the specimen must remain functional throughout the recovery period.
At the end of the specified duration, the specimen must remain in the testing chamber, where the temperature should gradually reach a value within the normal atmospheric conditions for the test The temperature variation in the testing chamber should not exceed 1 K per minute, averaged over a period not exceeding 5 minutes.
The specimen must undergo the recovery procedure in the testing chamber or another suitable location Appropriate steps should be taken to remove water droplets as specified, ensuring that the specimen remains undamaged.
Le spécimen doit ensuite être soumis aux conditions atmosphériques normales de reprise pendant une durée suffisante pour que la stabilité thermique soit atteinte, avec un minimum de 1 h
If the specific requirements dictate, the specimen must be energized or subjected to dissipation conditions and continuously measured throughout the recovery period.
Si les conditions atmosphériques normales de reprise indiquées ci-dessus ne sont pas appropriées pour le spécimen en essai, la spécification particulière peut prescrire d’autres conditions de reprise
Le spécimen doit être examiné visuellement et soumis aux vérifications électriques et mécaniques prescrites par la spécification particulière
7 Renseignements que doit fournir la spécification particulière
Lorsque l’Essai A : Froid est inclus dans la spécification particulière, les précisions suivantes doivent être spécifiées, dans la mesure ó elles sont applicables : a) type d’essai; b) pré-conditionnement; c) mesures initiales;
The relevant specification may require loading and measurements to be conducted during or at the conclusion of conditioning while the specimen remains in the chamber If these measurements are necessary, the specification must clearly outline the specific measurements and the timing for their execution, ensuring that the specimen is not removed from the chamber during this process.
To assess the performance of a specimen before the completion of the designated duration, an additional lot must be obtained for each specified duration It is essential to conduct recovery and final measurements separately for each lot.
During testing, the specimen must be turned off or unloaded before increasing the temperature, except for Test Ae, where the specimen remains operational throughout the recovery period.
At the conclusion of the designated time period, the specimen will stay in the chamber while the temperature is incrementally increased to a level that falls within standard atmospheric testing conditions It is essential that the temperature change rate within the chamber does not surpass the specified limit.
1 K per minute, averaged over a period of not more than 5 min
The specimen will undergo a recovery procedure in the chamber or another suitable method Necessary measures will be implemented to eliminate water droplets without causing any damage to the specimen.
The specimen shall then remain under standard atmospheric conditions for recovery for a period adequate for the attainment of temperature stability, with a minimum of 1 h
If required by the relevant specification, the specimen shall be switched on or loaded and measured continuously during the recovery period
If the standard conditions given above are not appropriate for the specimen to be tested, the relevant specification may call for other recovery conditions
The specimen shall be visually inspected and such performance checks made as are required by the relevant specification
7 Information to be given in the relevant specification
When Test A: Cold is specified, the following details must be provided as applicable: the type of test, preconditioning, initial measurements, severity, temperature and duration of exposure, temperature variation, dissipation measures or conditions during the test, recovery if abnormal, final measurements, any deviations from the method agreed upon by the client and supplier, and the temperature difference if low air speed was not established.
8 Renseignements que doit fournir le rapport d’essai
The test report must include essential information such as the client's name and address, the testing laboratory's name, address, and accreditation details (if applicable), as well as the test dates It should specify the type of test (Ab, Ad, Ae) and the purpose of the test (development, qualification, etc.) Additionally, the report must reference the testing standard and its edition (e.g., IEC 60068-2-1, edition *), along with the specific testing procedure used by the laboratory.
The article outlines essential components of a testing specimen, including the test specimen description with relevant diagrams and photos, and the quantity produced It details the identification of the testing chamber, specifying the manufacturer, model number, and identification number The performance of testing devices is highlighted, focusing on temperature control and air flow Additionally, it addresses the speed and direction of air impacting the specimen, the measurement uncertainty system, and calibration dates Initial, intermediate, and final measurements are documented, along with required and tested severities as per specific guidelines The performance results of the test specimens are presented, alongside observations made during testing and subsequent actions taken Finally, a summary of the test and its dissemination is provided.