This edition includes the following significant technical changes with respect to the previous edition: Type editorial changes technical changes Definitions deleted and moved to IEC 6
Level of protection (equipment protection level (EPL))
Electrical equipment featuring encapsulation "m" must meet one of the following protection levels: a) level "ma" (EPL "Ma, Ga, Da"), b) level "mb" (EPL "Mb, Gb, Db"), or c) level "mc" (EPL "Gc, Dc").
The requirements of this standard apply to all levels of protection for encapsulation “m” unless otherwise stated.
Additional requirements for levels of protection “ma” and “mb”
Components without additional protection shall be used only if they cannot damage the encapsulation mechanically or thermally in the case of any fault conditions specified in this standard
Alternatively, where a fault of an internal component may lead to failure of encapsulation “m” due to increasing temperature, the requirements of 7.9 shall apply.
Additional requirements for level of protection “ma”
The working voltage at any point in the circuit shall not exceed 1 kV
3.3 free surface compound surface exposed to the explosive atmospheres and/or dust layers
3.4 switching contact mechanical contact, which makes and breaks an electrical circuit
3.5 adhesion moisture, gas and dust tight permanent bonding of a compound to a surface
3.6 countable fault fault which occurs in parts of electrical equipment conforming to the constructional requirements
3.7 infallible separation separation between electrically conductive parts that is considered as not subject to short circuits
3.8 solid insulation insulation material which is extruded or moulded, but not poured
Note 1 to entry: Insulators fabricated from two or more pieces of electrical insulating material, which are solidly bonded together may be considered as solid
4.1 Level of protection (equipment protection level (EPL))
Electrical equipment featuring encapsulation "m" must meet one of the following protection levels: a) level "ma" (EPL "Ma, Ga, Da"), b) level "mb" (EPL "Mb, Gb, Db"), or c) level "mc" (EPL "Gc, Dc").
The requirements of this standard apply to all levels of protection for encapsulation “m” unless otherwise stated
4.2 Additional requirements for levels of protection “ma” and “mb”
Components without additional protection shall be used only if they cannot damage the encapsulation mechanically or thermally in the case of any fault conditions specified in this standard
Alternatively, where a fault of an internal component may lead to failure of encapsulation “m” due to increasing temperature, the requirements of 7.9 shall apply
4.3 Additional requirements for level of protection “ma”
The working voltage at any point in the circuit shall not exceed 1 kV.
Rated voltage and prospective short circuit current
The rated voltage and prospective short circuit current must be defined to ensure that the limiting temperature is not surpassed for the applicable protection levels "ma," "mb," or "mc."
General
The documentation shall specify the compound(s) used and the processing method(s), including measures to prevent the formation of voids
As a minimum, those properties of the compound(s) on which encapsulation “m” depends shall be provided
NOTE Proper selection of the compound allows for the expansion of components during operation and in the event of allowable faults.
Specification
The compound specification must include the manufacturer's name and address, a complete reference of the compound with details on fillers and additives, and any surface treatments like varnishing It should outline pre-treatment requirements for proper adhesion, such as cleaning or etching, and specify the dielectric strength per IEC 60243-1 at the maximum service temperature Additionally, the temperature range, including maximum and minimum continuous operating temperatures, must be stated For "m" equipment, the temperature index (TI) value or relative thermal index (RTI-mechanical) should be provided, along with the color of the compound affecting the specification and thermal conductivity if an alternative test method is used.
NOTE It is not a requirement of this standard that conformity to the manufacturer’s specification of the compound needs to be verified.
Properties of the compound
Water absorption
The compound must be tested as per section 8.1.1; if testing is not conducted, the equipment's certificate number must feature an “X” suffix in line with IEC 60079-0 marking requirements Additionally, the certificate should specify the necessary precautions for its specific conditions of use.
Dielectric strength
If the dielectric strength of the compound at the maximum service temperature, as specified in IEC 60243-1 section 8.2.2 a), is not provided by the material manufacturer, a test must be conducted following the guidelines outlined in section 8.1.2.
NOTE It is not a requirement of this standard that conformity to the manufacturer`s specification of the compound needs to be verified
General
The service temperature of the compound must not exceed the maximum value of the compound's COT, as specified by IEC 60079-0 Additionally, the maximum surface temperature should be assessed under both normal operation and fault conditions, following the guidelines in section 7.2.1 of IEC 60079-0 It is essential to ensure that the encapsulation "m" equipment is adequately protected to prevent any adverse effects during these fault conditions.
Determination of the limiting temperatures
Maximum surface temperature
The maximum surface temperature shall be determined using the test method given in 8.2.2 in accordance with the supply conditions specified in 4.4
The specified temperature is crucial for identifying the temperature class for explosive gas atmospheres and determining the maximum surface temperature in degrees Celsius for explosive dust atmospheres of the equipment, or both.
Temperature of the compound
The hottest component shall be determined The maximum temperature in the compound, adjacent to the hottest component, shall be determined using the test method given in 8.2.2 for normal operation
To determine the temperature of the hottest component during normal operation, one can use calculations, refer to the manufacturer's specifications, or test the component under its intended application conditions before encapsulation, provided that the thermal conductivity of the compound exceeds that of air.
NOTE Thermal conductivity of air is most often defined as 0.25 W/m*K (standard conditions).
Temperature limitation
When assessing equipment for potential faults as outlined in section 7.2.1, it is crucial to consider scenarios that may lead to elevated temperatures This includes situations arising from unfavorable input voltage or load conditions, which must be factored into the evaluation of limiting temperatures.
A protective device is necessary to limit temperatures for safety, and it can be either an external electrical or thermal device or one that is directly integrated into the equipment, as specified in section 7.9.
General
Where the compound forms part of the external enclosure it shall comply with the requirements of IEC 60079-0 for non metallic enclosures and non metallic parts of enclosures
Enclosures that fully or partially surround a compound must adhere to the enclosure requirements outlined in IEC 60079-0, as they are integral to the protection of the surface.
Additional protective measures may be required to be provided by the user in the installation in order to comply with the requirements of this standard For example, additional mechanical
NOTE It is not a requirement of this standard that conformity to the manufacturer`s specification of the compound needs to be verified
The service temperature of the compound must not exceed the maximum value of the compound's COT, as specified by IEC 60079-0 Additionally, the maximum surface temperature should be assessed under both normal operation and fault conditions, following the guidelines in section 7.2.1 of IEC 60079-0 It is essential that the "m" equipment is adequately protected to ensure that encapsulation "m" remains unaffected during these fault conditions.
6.2 Determination of the limiting temperatures
The maximum surface temperature shall be determined using the test method given in 8.2.2 in accordance with the supply conditions specified in 4.4
The specified temperature is crucial for identifying the temperature class for explosive gas atmospheres and determining the maximum surface temperature in degrees Celsius for explosive dust atmospheres of the equipment.
The hottest component shall be determined The maximum temperature in the compound, adjacent to the hottest component, shall be determined using the test method given in 8.2.2 for normal operation
To determine the temperature of the hottest component during normal operation, one can use calculations, refer to the manufacturer's specifications, or test the component under its intended application conditions before encapsulation, provided that the thermal conductivity of the compound exceeds that of air.
NOTE Thermal conductivity of air is most often defined as 0.25 W/m*K (standard conditions)
When assessing equipment for potential faults as outlined in section 7.2.1, it is crucial to consider scenarios that may lead to elevated temperatures This includes unfavorable input voltage or load conditions, which must be factored into the evaluation of limiting temperatures.
A protective device must be utilized to limit temperatures for safety, which can either be an external electrical or thermal device or one that is directly integrated into the equipment, as specified in section 7.9.
Where the compound forms part of the external enclosure it shall comply with the requirements of IEC 60079-0 for non metallic enclosures and non metallic parts of enclosures
Enclosures that fully or partially surround a compound must adhere to the enclosure requirements outlined in IEC 60079-0, as they are integral to the protection of the surface.
To meet the standard's requirements, users may need to implement extra protective measures during installation This could include additional mechanical protection to shield the equipment from direct impacts In these instances, the equipment's certificate number must feature an “X” suffix, as specified by the marking requirements of IEC 60079-0 Furthermore, the certificate should outline the specific conditions of use and necessary precautions.
Appropriate action shall be taken to accommodate the expansion of components during normal operation and in the event of faults according to 7.2
In sections 7.2 to 7.9, the requirements vary based on the compound's adhesion to the enclosure Adhesion is crucial to prevent the entry of explosive atmospheres and moisture at boundary surfaces, such as between the enclosure and the compound, as well as for components like printed wiring boards and connection terminals It is essential that adhesion is maintained after all required tests to ensure the type of protection remains intact The selection of compounds for specific applications depends on their intended functions, and testing a compound for one application does not qualify it for all uses.
NOTE Tests for adhesion are under consideration.
Determination of faults
Fault examination
According to IEC 60079-0 standards, encapsulation "m" must be preserved under the most unfavorable output load conditions, allowing for up to two internal countable faults for protection level "ma" and one internal countable fault for protection level "mb," as specified in sections 7.2.2, 7.2.3, and 7.2.4.
No faults are taken into account for level of protection “mc”
Faults can manifest in various ways, including short circuits in components, failures of individual components, and faults occurring between tracks on a printed wiring board, although track openings do not qualify as faults.
The failure of some components may result in an unstable condition, for example, alternating between high and low resistance In those cases, the most onerous condition shall be considered
If a fault leads to one or more subsequent faults, for example, due to the overload of a component, the primary and subsequent fault(s) shall be considered to be a single fault.
Components considered as not subject to fail
For protection levels "ma" and "mb," components are deemed reliable if they meet encapsulation standards, are appropriate for the service temperature, and operate at no more than two-thirds of their rated voltage, current, and power, considering the device's rating, mounting conditions, and specified temperature range.
– resistors, – single-layer, spirally wound coils, – plastic foil capacitors,
– paper capacitors, – ceramic capacitors, – semiconductors, – semiconductor devices used as a protective device according to 7.9,
– resistors used as a protective device according to 7.9, if they comply with the current limiting resistors of IEC 60079-11 for level of protection “ia” or “ib”
Windings classified as “ma” and “mb” under IEC 60079-7, including those with wire diameters smaller than 0.25 mm, are deemed to be failure-resistant when encapsulated in accordance with the standard's specifications.
Isolating components
The following components for the segregation of different circuits shall be considered to provide isolation and are not considered to fail across the segregation:
• Galvanically separating components (e.g optocouplers and relays),
The rated insulation voltage must meet the requirement of either 2U + 1,000 V r.m.s + 50% or 1,500 V r.m.s., whichever is greater, where U represents the sum of the rated r.m.s voltages of both circuits Additionally, for rated insulation voltages exceeding 60 V, optocouplers and relays that provide double or reinforced insulation between the circuits must comply with IEC 61140 standards.
– complying with IEC 60079-11 for level of protection “ia” or “ib”
– providing a double or reinforced insulation between the circuit per IEC 61558-1, or – complying with IEC 60079-11 for level of protection “ia” or “ib”
NOTE 1 It is not a requirement of this standard that conformity to the above standards per the manufacturer´s specification regarding segregation needs to be verified
NOTE 2 Galvanically separating components providing double or reinforced insulation according to a product standard are considered to meet the requirements of IEC 61140 e.g IEC 60747-5-5 for optocouplers.
Infallible separation distances
It is not necessary to consider the possibility of a fault occurring as described in 7.2.1 in respect of voltage breakdown, if the distances between bare current-carrying parts:
– of the same circuit, or
– of a circuit and earthed metal parts, or
For two distinct circuits, the total working voltage is determined by summing the individual voltages, as outlined in Table 1 If one voltage is less than 20% of the other, it will be disregarded Additionally, these circuits must adhere to the stipulations of sections 7.2.4.2 and, if relevant, 7.2.4.3.
Distances within a compound are deemed reliable against short circuits for protection levels "ma" and "mb" if they meet the specifications outlined in Table 1, provided that these distances are either fixed or mechanically secured prior to encapsulation.
When a properly adhered non-metallic enclosure meets the specified minimum thickness, allowing for a zero thickness of compound as indicated in Key letter c of Table 4 and Figure 1, the separation distances for the related current-carrying components remain reliable in preventing short circuits.
The distances specified for the minimum protection level "mc" and the infallible distances for protection levels "ma" and "mb" are not deemed infallible.
– resistors used as a protective device according to 7.9, if they comply with the current limiting resistors of IEC 60079-11 for level of protection “ia” or “ib”
Windings classified as “ma” and “mb” under IEC 60079-7, including those with wire diameters smaller than 0.25 mm, are deemed to be failure-free if they are encapsulated in accordance with the standard's specifications.
The following components for the segregation of different circuits shall be considered to provide isolation and are not considered to fail across the segregation:
• Galvanically separating components (e.g optocouplers and relays),
– if the rated insulation voltage conforms to 2U + 1 000 V r.m.s + 5 0 % or 1 500 V r.m.s whichever is greater (U is the sum of the rated r.m.s voltages of both circuits), or
For insulation voltages exceeding 60 V across circuit segregation, it is essential to use optocouplers and relays that offer double or reinforced insulation between the circuits, in accordance with IEC 61140 standards.
– complying with IEC 60079-11 for level of protection “ia” or “ib”
– providing a double or reinforced insulation between the circuit per IEC 61558-1, or
– complying with IEC 60079-11 for level of protection “ia” or “ib”
NOTE 1 It is not a requirement of this standard that conformity to the above standards per the manufacturer´s specification regarding segregation needs to be verified
NOTE 2 Galvanically separating components providing double or reinforced insulation according to a product standard are considered to meet the requirements of IEC 61140 e.g IEC 60747-5-5 for optocouplers
It is not necessary to consider the possibility of a fault occurring as described in 7.2.1 in respect of voltage breakdown, if the distances between bare current-carrying parts:
– of the same circuit, or
– of a circuit and earthed metal parts, or
– of two separate circuits (sum of the working voltages shall be taken as the voltage for
Table 1; where one of the working voltages is less than 20 % of the other, it shall be ignored), comply with the requirements of 7.2.4.2 and if applicable 7.2.4.3
Distances within a compound are deemed reliable against short circuits for protection levels "ma" and "mb" if they adhere to the values specified in Table 1, provided that these distances are fixed or mechanically secured prior to encapsulation.
When a properly adhered non-metallic enclosure meets the specified minimum thickness, allowing for a zero thickness of compound as indicated in Key letter c of Table 4 and Figure 1, the separation distances for the related current-carrying components remain reliable against short circuits.
The distances specified for the minimum protection level "mc" and the infallible distances for protection levels "ma" and "mb" are not deemed infallible and must be evaluated as a "countable fault." Distances that fall below the minimum for protection level "mc" are classified as short-circuits if they compromise the protection type "m."
For level of protection “mc” the values of Table 1 are the constructional requirements and may be achieved by mechanically fixing before encapsulation
Table 1 – Distances through the compound
The voltages presented are based on IEC 60664-1, specifically rationalized supply voltages from Table 3b When calculating the necessary distance, the working voltage can exceed the table value by a factor of 1.1.
The factor of 1.1 acknowledges that in various locations within a circuit, the operating voltage matches the rated voltage Additionally, it accommodates several commonly used rated voltages through this 1.1 factor.
The distance through solid insulation, on which the type of protection “m” depends, shall be at least 0,1 mm and shall comply with the dielectric strength test of 8.2.4.
Free space in the encapsulation
Group III “m” equipment
The total amount of free spaces is unlimited; however, each individual free space is restricted to a maximum volume of 100 cm³ Additionally, the thickness of the compound encasing these free spaces must adhere to the specifications outlined in Table 2.
Table 2 – Minimum thickness of compound adjacent to free space for Group III “m” equipment
Level of protection Minimum thickness of compound adjacent to free space to:
Free space or free surface 3 mm 3 mm
Non-metallic or metal enclosure with adhesion 3 mm (enclosure + compound) a 3 mm (enclosure + compound) a Non-metallic or metal enclosure without adhesion 3 mm 3 mm
Free space or free surface 1 mm 3 mm
Non-metallic or metal enclosure with adhesion 1 mm (enclosure + compound) 3 mm (enclosure + compound) a
Non-metallic or metal enclosure without adhesion 1 mm 3 mm
Free space or free surface 1 mm 1 mm
“mc” Non-metallic or metal enclosure with adhesion 1 mm (enclosure + compound) 1 mm (enclosure + compound) Non-metallic or metal enclosure without adhesion 1 mm 1 mm a Wall thickness of the enclosure ≥ 1 mm
The thickness of the materials quoted in this table does not imply compliance with other mechanical tests required by IEC 60079-0
NOTE A metal enclosure with adhesion is permitted to have no compound thickness to a free space provided there are no live parts in the free space.
Group I and Group II “m” equipment
The sum of the free spaces shall not exceed:
• 100 cm 3 for level of protection “mb” and “mc”;
• 10 cm 3 for level of protection “ma”
The minimum thickness of the compound surrounding such free spaces shall comply with Table 3
Table 2 – Minimum thickness of compound adjacent to free space for Group III “m” equipment
Level of protection Minimum thickness of compound adjacent to free space to:
Free space or free surface 3 mm 3 mm
Non-metallic or metal enclosure with adhesion 3 mm (enclosure + compound) a 3 mm (enclosure + compound) a Non-metallic or metal enclosure without adhesion 3 mm 3 mm
Free space or free surface 1 mm 3 mm
Non-metallic or metal enclosure with adhesion 1 mm (enclosure + compound) 3 mm (enclosure + compound) a
Non-metallic or metal enclosure without adhesion 1 mm 3 mm
Free space or free surface 1 mm 1 mm
“mc” Non-metallic or metal enclosure with adhesion 1 mm (enclosure + compound) 1 mm (enclosure + compound) Non-metallic or metal enclosure without adhesion 1 mm 1 mm a Wall thickness of the enclosure ≥ 1 mm
The thickness of the materials quoted in this table does not imply compliance with other mechanical tests required by IEC 60079-0
NOTE A metal enclosure with adhesion is permitted to have no compound thickness to a free space provided there are no live parts in the free space
7.3.2 Group I and Group II “m” equipment
The sum of the free spaces shall not exceed:
• 100 cm 3 for level of protection “mb” and “mc”;
• 10 cm 3 for level of protection “ma”
The minimum thickness of the compound surrounding such free spaces shall comply with
Table 3 – Minimum thickness of compound adjacent to free space for Group I and Group II “m” equipment
Minimum thickness of compound adjacent to free space to:
Free space or free surface 3 mm 3 mm
(pressure test in accordance with 8.2.6)
Non-metallic or metal enclosure with adhesion 3 mm (enclosure + compound) a 3 mm (enclosure + compound) a (pressure test in accordance with 8.2.6)
Non-metallic or metal enclosure without adhesion
(pressure test in accordance with 8.2.6)
Free space or free surface 1 mm 3 mm 3 mm
(pressure test in accordance with 8.2.6)
Non-metallic or metal enclosure with adhesion 1 mm (enclosure + compound) 3 mm (enclosure + compound) a
3 mm (enclosure + compound) a (pressure test in accordance with 8.2.6)
Non-metallic or metal enclosure without adhesion
(pressure test in accordance with 8.2.6)
Free space or free surface 1 mm 1 mm 3 mm
“mc ” Non-metallic or metal enclosure with adhesion 1 mm (enclosure + compound) 1 mm (enclosure + compound) 3 mm (enclosure + compound) See note
Non-metallic or metal enclosure without adhesion
1 mm 1 mm 3 mm a Wall thickness of the enclosure ≥ 1 mm
The thickness of the materials quoted in this table does not imply compliance with other mechanical tests required by IEC 60079-0
NOTE A metal enclosure with adhesion is permitted to have no compound thickness to a free space provided there are no live parts in the free space.
Thickness of the compound
Windings for electrical machines
For electrical machines featuring windings in slots, solid slot insulation must adhere to specific requirements: a minimum thickness of 0.1 mm is necessary for protection level "ma," extending at least 5 mm beyond the slot's end For protection levels "ma" and "mb," both the slot end and end-winding require a minimum thickness of compound as specified in section 7.4.1 Additionally, a dielectric strength test must be conducted in accordance with section 8.2.4, using a test voltage of U = 2U.
1 000 V r.m.s + 5 0 % with a minimum of 1 500 V a.c at 48 Hz to 62 Hz
Varnish and similar coatings are not considered to be solid insulation.
Rigid, multi-layer printed wiring boards with through connections
Multi-layer printed wiring boards that adhere to IEC 62326-4-1, performance level C, or IPC-A-600 and IPC-6012 or ANSI/UL 796, and operate at working voltages of 500 V or less, are classified as encapsulated if they comply with section 7.4.3.2.
NOTE It is not a requirement of this standard that conformity to the manufacturer`s performance specification of the printed wiring board needs to be verified
The insulation thickness of both, the copper-clad laminates and the adhesive films shall comply with the requirements of 7.2.4.3
NOTE The insulation thickness is the combination of the laminate and the adhesive film when they are not separated by copper
The minimum spacing between printed circuit conductors and the edges or holes of a multi-layer printed wiring board must adhere to the distances specified in Table 5 If the edges or holes are shielded with metal or insulating material that extends at least 1 mm from the surface, the required distance between the conductors and this protective material can be reduced to the values indicated as distance c in Table 5 Additionally, any metal coating applied must have a minimum thickness of 35 µm, as detailed in Figure 2 and Table 5.
Table 5 – Minimum distances for multi-layer printed wiring boards
The distance levels of protection for electrical components are categorized into three types: "ma," "mb," and "mc." The specified distances are as follows: for "ma," the distance is 3 mm; for "mb," it varies from 0.5 mm to 3 mm; and for "mc," it ranges from 0.25 mm to 1 mm Additionally, specific thicknesses of 0.1 mm are referenced in section 7.2.4.3 The distances are defined as follows: "a" represents the distance between the current-carrying part and the outer surface through the cover layer; "b" is the distance along the cover layer; "c" indicates the length of metal or insulation extending from the edge or hole; "d" refers to the thickness of the adhesive film or core where segregation is necessary; and "e" denotes the distance between two circuits within a multilayer structure where segregation is required.
Key core and cover layer adhesive film copper
2 Through contact to connect the printed conductors to the layers
Figure 2 – Minimum distances for multi-layer printed wiring boards
Switching contacts
General
Switching contacts shall be provided with an additional enclosure
The minimum spacing between printed circuit conductors and the edges or holes of a multi-layer printed wiring board must adhere to the distances specified in Table 5 If the edges or holes are shielded with metal or insulating material that extends at least 1 mm from the surface, the required distance between the conductors and this protective material can be reduced to the values indicated as distance c in Table 5 Additionally, any metal coating applied must have a minimum thickness of 35 µm, as detailed in Figure 2 and Table 5.
Table 5 – Minimum distances for multi-layer printed wiring boards
The distance levels of protection for electrical components are categorized into three types: "ma," "mb," and "mc." The specified distances are as follows: for "ma," the distance is 3 mm; for "mb," it varies from 0.5 mm to 3 mm; and for "mc," it ranges from 0.25 mm to 1 mm Additionally, specific guidelines are referenced in section 7.2.4.3 for thicknesses of 0.1 mm The distances are defined as follows: "a" represents the distance between the current-carrying part and the outer surface through the cover layer; "b" is the distance along the cover layer; "c" indicates the length of metal or insulation extending from the edge or hole; "d" refers to the thickness of the adhesive film or core where segregation is necessary; and "e" denotes the distance between circuits within a multilayer structure requiring segregation.
Key core and cover layer adhesive film copper
2 Through contact to connect the printed conductors to the layers
Figure 2 – Minimum distances for multi-layer printed wiring boards
Switching contacts shall be provided with an additional enclosure
NOTE Entering of compound in the enclosure of the switching contacts during the encapsulation process can interfere with the function of the device
Level of protection “ma”
This additional enclosure shall be in accordance with the requirements for hermetically-sealed devices as defined in IEC 60079-15 before encapsulation
NOTE Damage to the hermetically-sealed enclosure due to stresses during potting can invalidate the type of protection of the device
Switching contacts must have a rating of 60 V and 6 A or lower If the switched current exceeds two-thirds of the manufacturer's specified rated current, an additional enclosure made of inorganic material is required.
Level of protection “mb”
If the switched current surpasses 2/3 of the manufacturer's rated current or exceeds 6 A, an additional enclosure made of inorganic material is required.
Level of protection “mc”
This additional enclosure shall be made of inorganic material if the switched current exceeds
External connections
General
When compounds are used to secure a permanently connected cable, the cable shall be suitably protected against damage from flexing and the pull test shall be carried out according to 8.2.5
This test shall not be performed on Ex Components or where the enclosure of the “m” protected device does not serve as an external enclosure.
Additional requirements for “ma” equipment
Ex ma equipment must be supplied by a circuit that meets the "ia" protection level as specified in IEC 60079-11, or it should comply with one of the following connection requirements.
• for EPL Ga requirements of IEC 60079-26;
• for EPL Da, level of protection “ta” of IEC 60079-31.
Protection of bare live parts
To ensure compliance with the required Equipment Protection Level (EPL), bare live parts that penetrate the surface of the compound must be safeguarded by an additional protection method as specified in IEC 60079-0.
NOTE In this case, the equipment is marked with multiple types of protection in accordance with IEC 60079-0.
Cells and batteries
General
When assessing battery control systems for gas release risks, it is essential to consider the complete spectrum of operating temperatures, internal resistance, and voltage capacity It is important to acknowledge that batteries may become unbalanced; however, cells with minimal resistance or voltage capability can be disregarded.
Subclause 7.8 applies to all levels of protection, unless specifically excluded
Cells and batteries classified under the protection level "ma" must adhere to the requirements outlined in IEC 60079-11, with the exception of the allowance for parallel cells, which is not permitted in equipment that relies solely on encapsulation for protection.
Prevention of gassing
Electrochemical systems that emit gas during normal operation are prohibited For protection levels "ma" and "mb," if gas release cannot be avoided in the event of a fault, it must be minimized by a control device as specified in section 7.8.8 This control device must be effective during both charging and discharging of secondary cells, including when charging occurs outside hazardous areas.
Vented cells and sealed valve regulated cells are prohibited for use, while sealed gas-tight cells that do not emit gas under any operating or fault conditions within the ambient temperature range of the electrical equipment are permitted without a control device, as specified in section 7.8.8.
Gas-tight cells that do not fulfil the requirements of 7.8.2 c) shall have a control device in accordance with 7.8.8.
Protection against inadmissible temperatures and damage to the cells
The maximum service temperature for cells or batteries under worst-case load conditions must not exceed the manufacturer's specified temperature or 80 °C if no specification is provided Additionally, the maximum charging and discharging current should not surpass the safe value indicated by the manufacturer This can be achieved by implementing control devices to prevent overheating or gassing, or by using a series resistor to limit current to the cell rating along with a blocking diode to prevent reverse charging.
In either case, the requirements in 7.8.4 through 7.8.7 apply as applicable.
Reverse current
For protection levels "ma" and "mb," it is essential to safeguard the encapsulated cell or battery and its circuits from unintended charging by other voltage sources within the same enclosure This can be achieved by either isolating the cell or battery from all other voltage sources using specified distances from Table 1, or by separating the cell or battery with one blocking diode for level "mb" or two blocking diodes for level "ma," as illustrated in Figure 3 This arrangement minimizes the risk of a single fault short-circuiting both diodes.
Subclause 7.8 applies to all levels of protection, unless specifically excluded
For the "ma" level of protection, cells and batteries must meet the requirements outlined in IEC 60079-11, with the exception that parallel cells are not allowed in equipment that relies solely on encapsulation for protection.
Electrochemical systems that emit gas during normal operation are prohibited For protection levels "ma" and "mb," if gas release cannot be avoided in the event of a fault, it must be minimized by a control device as specified in section 7.8.8 This control device must be effective during both charging and discharging of secondary cells, including when charging occurs outside hazardous areas.
Vented cells and sealed valve regulated cells are prohibited for use; however, sealed gas-tight cells that do not emit gas under any operating or fault conditions within the ambient temperature range of the electrical equipment may be utilized without a control device, as specified in section 7.8.8.
Gas-tight cells that do not fulfil the requirements of 7.8.2 c) shall have a control device in accordance with 7.8.8
7.8.3 Protection against inadmissible temperatures and damage to the cells or batteries
The maximum service temperature for cells or batteries under worst-case load must not exceed the manufacturer's specified temperature or 80 °C if unspecified Additionally, the maximum charging and discharging current should not surpass the safe value indicated by the manufacturer This can be achieved by implementing control devices to prevent overheating or gassing, or by using a series resistor to limit current to the cell rating along with a blocking diode to prevent reverse charging.
In either case, the requirements in 7.8.4 through 7.8.7 apply as applicable
For protection levels "ma" and "mb," it is essential to safeguard the encapsulated cell or battery and its circuits from unintended charging by other voltage sources within the same enclosure This can be achieved by either isolating the cell or battery from all other voltage sources using specified distances from Table 1, or by separating the cell or battery alone with the appropriate distances while incorporating one blocking diode for level "mb" or two blocking diodes for level "ma." The arrangement of these diodes, as illustrated in Figure 3, should minimize the risk of a single fault leading to both diodes being short-circuited.
NOTE Figure shows arrangement for Level of Protection “ma”
Figure 3 – Fitting of blocking diodes
Current limitation
The maximum surface temperature must be established based on the highest discharge current allowed by the equipment manufacturer's maximum load or the protective device, which can be 1.7 times the fuse rating If no load or protective device is specified, the temperature should be determined at short circuit conditions.
To prevent exceeding the maximum discharge current specified by the cell or battery manufacturer, a resistor, current limiting device, or fuse in accordance with IEC 60127, IEC 60691, or ANSI/UL 248 series should be utilized Additionally, if replaceable fuses are employed, the equipment must be clearly marked to indicate their rating and function.
NOTE It is not a requirement of this standard that conformity to the manufacturer`s specification of the resistor, current limiting device or fuse needs to be verified.
Protection against the polarity inversion and deep discharge of the cells
For protection levels "ma" and "mb," it is essential to monitor the cell voltage when more than three cells are connected in series If the voltage drops below the manufacturer's specified limit during discharging, the control device must disconnect the cells or battery In the case of protection level "mc," precautions should be implemented to prevent reverse polarity charging when more than three cells are in series.
NOTE 1 If several cells are connected in series, cells can change polarity during discharge due to the various capacities of the cells in a battery These "reversed pole“ cells can enter an inadmissible gassing range.
A deep discharge protection circuit is essential to prevent reverse polarity charging of cells during discharge The minimum cut-off voltage must align with the specifications provided by the cell or battery manufacturer Once the load is disconnected, the current should not exceed the discharge capacity at the 1,000-hour rate.
NOTE 2 Such protection is often used to prevent cells going into a state of “deep discharge” If an attempt is made to monitor too many cells connected in series, the protection will sometimes not function reliably due to tolerances in individual cell voltages and the protection circuit Generally, monitoring of more than six cells (in series) by one protection unit is not effective.
Charging of cells or batteries
The charging circuits must be fully specified as part of the equipment The charging system should ensure that, in the event of a fault, the charging voltage and current remain within the manufacturer's specified limits Additionally, if there is a risk of exceeding the manufacturer's limits for cell voltage or charging current during charging, a separate protective device must be installed to prevent gas release and to avoid surpassing the maximum rated cell temperature.
The charging system must ensure that the voltage and current during normal operation do not exceed the manufacturer's specified limits for the designated temperature range When charging cells and batteries integral to electrical equipment in hazardous areas, the charger must be fully defined as part of the equipment design Conversely, if these cells or batteries are charged outside of hazardous areas, the charging process must still adhere to the manufacturer's specified limits.
Requirements for control safety devices for cells or batteries
Control devices must be integral components of a safety-related control system It is the manufacturer's responsibility to supply the necessary information to ensure the system's integrity.
NOTE Safety related parts meeting the requirements of PL c of ISO 13849-1 “Safety of machinery – Safety related parts of control systems – Part 1: General principles for design” will satisfy this subclause.
Protective devices
General
When using a protective device to control maximum surface temperature for equipment under single fault (level “mb”) or double fault (level “ma”) conditions, the device must be either externally mounted or integrated within the equipment For level “ma” protection, the thermal protective devices must be non-resettable, while those for level “mb” may be resettable.
The protective device must effectively interrupt the maximum fault current of the circuit it is installed in, and its rated voltage should at least match the working voltage of that circuit.
The "m" equipment includes a cell or battery along with a control device designed to prevent excessive overheating This control device serves as a protective mechanism, ensuring that all other components within the same unit do not exceed the maximum surface temperature.
NOTE 1 The use of protective devices is to protect against faults and unforeseen overloads, which overheat and/or permanently damage or compromise the operational life of the equipment Where resettable devices are used, the instructions include information to guide the user in the desirability of re-setting the devices These instructions are considering external operational conditions under which they might be reset and also any subsequent monitoring that might be desirable
NOTE 2 Both, self-resetting and manually resettable devices are considered to be resettable devices for the purpose of this standard
For the "ma" level of protection, a single non-resettable protective device is sufficient if it meets the standards set by the IEC 60127 series, IEC 60691, or ANSI/UL 248 series, as outlined in sections 7.9.2 and 7.9.3.
NOTE 3 It is not a requirement of this standard that conformity to the manufacturer`s specification of the non resettable protective device needs to be verified
NOTE 4 ANSI/UL 248-1 contains the applicable general safety requirements for low-voltage fuses, including the requirements to establish breaking capacity or interrupting rating The other parts of the ANSI/UL 248 series provide additional specific safety requirements based on the intended application of the fuse, such as ANSI/UL 248-14 for supplemental low-voltage fuses
The charging system must ensure that the voltage and current during normal operation do not exceed the manufacturer's specified limits for the designated temperature range When charging cells and batteries integral to the electrical equipment in hazardous areas, the charger must be fully detailed in the equipment design Conversely, if these cells or batteries are charged outside of hazardous areas, the charging process must still adhere to the manufacturer's specified limits.
7.8.8 Requirements for control safety devices for cells or batteries
Control devices must serve as safety-related components within a control system It is the manufacturer's responsibility to supply the necessary information to ensure the system's integrity.
NOTE Safety related parts meeting the requirements of PL c of ISO 13849-1 “Safety of machinery – Safety related parts of control systems – Part 1: General principles for design” will satisfy this subclause
When using a protective device to control maximum surface temperature for equipment under single fault (level "mb") or double fault (level "ma") conditions, the device must be either externally mounted or integrated within the equipment For level "ma" protection, the thermal protective devices must be non-resettable, while those for level "mb" may be designed to be resettable.
The protective device must effectively interrupt the maximum fault current of the circuit it is installed in, and its rated voltage should at least match the working voltage of that circuit.
The "m" equipment includes a cell or battery along with a control device designed to prevent excessive overheating This control device serves as a protective mechanism, ensuring that all other components within the same unit do not exceed the maximum surface temperature.
NOTE 1 The use of protective devices is to protect against faults and unforeseen overloads, which overheat and/or permanently damage or compromise the operational life of the equipment Where resettable devices are used, the instructions include information to guide the user in the desirability of re-setting the devices These instructions are considering external operational conditions under which they might be reset and also any subsequent monitoring that might be desirable
NOTE 2 Both, self-resetting and manually resettable devices are considered to be resettable devices for the purpose of this standard
For level of protection “ma”, if the non resettable protective device complies with the
IEC 60127 series or IEC 60691 or ANSI/UL 248 series, only one device is necessary This applies to 7.9.2 and 7.9.3
NOTE 3 It is not a requirement of this standard that conformity to the manufacturer`s specification of the non resettable protective device needs to be verified
NOTE 4 ANSI/UL 248-1 contains the applicable general safety requirements for low-voltage fuses, including the requirements to establish breaking capacity or interrupting rating The other parts of the ANSI/UL 248 series provide additional specific safety requirements based on the intended application of the fuse, such as ANSI/UL
248-14 for supplemental low-voltage fuses.
Electrical protective devices
Protective devices must be rated for a voltage that meets or exceeds the circuit's voltage and should possess a breaking capacity that is equal to or greater than the circuit's fault current.
A fuse is typically rated to handle 1.7 times its rated current continuously, ensuring that the maximum surface temperature is not exceeded according to the manufacturer's specifications For electrical protective devices, two devices in series are required for protection level "ma," while one device suffices for level "mb." If the two devices for level "ma" are not in series, the activation of either device must de-energize the circuitry that relies on this protection Additionally, both devices for level "ma" should be of the same type, although they can be from different manufacturers or part numbers, to ensure duplicated protection.
An electrical protective device is not required for level of protection “mc”
NOTE In the case of electrical supply networks where the rated voltage does not exceed 250 V, the prospective short-circuit fault current is usually 1 500 A
7.9.2.2 Protective devices that are connected to the “m” equipment
External protective devices for "m" equipment are considered essential for its safety, as outlined in section 7.9.2 This condition must be documented on the certificate, and the equipment should be marked according to the specific conditions of use as per IEC 60079-0 standards.
The use of an external protective device and its connection to “m” equipment requires the device to be compatible with “ma”, “mb”, or “mc” as appropriate
Using a protective device as intended is crucial to maintain the required level of protection When an external protective device regulates voltage, current, and power for equipment with a protection level of "ma," it ensures safety even with one identifiable fault The allowable voltage, current, and power levels are based on the thermal characteristics of the "m" equipment.
Thermal protective devices
Thermal protective devices shall be used to protect the compound from damage caused by local heating, for example, by faulty components, or from exceeding the maximum surface temperature
Non-resettable devices are designed to permanently open a circuit when exposed to temperatures exceeding their specified operating limits for a certain duration It is essential to ensure proper thermal coupling between the monitored component and the thermal protective device Additionally, the device's switching capability must be clearly defined and should meet or exceed the maximum load of the circuit.
For level of protection "mb," two resettable thermal protective devices must be used in series, while only one device is needed for level "mc." If the two devices for level "mb" are not in series, the activation of either device will de-energize the dependent circuitry Additionally, both devices for level "mb" should be of the same type, although they can be from different manufacturers or part numbers, to ensure duplicated protection.
Resettable thermal protective devices with switching contacts shall not be operated at more than 2/3 of their rated current specified by the manufacturer of the device
Resettable thermal protective devices with switching contacts shall either comply with IEC 60730-2-9, or shall be tested according to 8.2.7.1
Resettable thermal protective devices without switching contacts shall either comply with IEC 60738-1, or shall be tested according to 8.2.7.2
NOTE 1 Often for functional reasons, additional resettable devices other than the thermal protective devices addressed by this clause are used These devices typically operate at temperatures lower than the operating temperature of the thermal protective device
NOTE 2 It is not a requirement of this standard that conformity to the manufacturer`s specification of the resettable thermal protective device needs to be verified.
Built-in protective devices
Protective devices integral with the “m” equipment shall be of the enclosed type such that no compound can enter during the encapsulation process
The suitability of the protective device for encapsulation shall be confirmed either by: a) a documentation from the manufacturer of the device; or b) testing of samples according 8.2.8
NOTE Devices in glass, plastic, ceramic or otherwise sealed are regarded as enclosed types
Tests on the compound
Water absorption test
When required by 5.3.1 the test shall be carried out on samples of the compound(s) used in
Three dry samples of the compound(s) will be tested, each circular with a diameter of 50 mm ± 1 mm and a thickness of 3 mm ± 0.2 mm After weighing, the samples will be immersed in water at 23 °C ± 0.2 K for a minimum of 24 hours Following immersion, the samples will be removed, wiped dry, and weighed again within one minute The increase in mass must not exceed 1%.
It is not required to use distilled water for this test.
Dielectric strength test
The sample shall be circular with a diameter of 50 mm ± 1 mm and a thickness of
3 mm ± 0,2 mm The sample shall be symmetrically placed between electrodes 30 mm ± 1 mm in diameter, within a temperature controlled oven, set to achieve the maximum service temperature of the compound
A voltage of 4 kV r.m.s + 5 0 % and with frequency between 48 Hz and 62 Hz shall be applied for not less than 5 min No flashover or breakdown shall occur during the test.
Tests on the apparatus
Test sequence
The test sequence and number of samples are given in Annex B
Resettable thermal protective devices with switching contacts shall either comply with
IEC 60730-2-9, or shall be tested according to 8.2.7.1
Resettable thermal protective devices without switching contacts shall either comply with
IEC 60738-1, or shall be tested according to 8.2.7.2
NOTE 1 Often for functional reasons, additional resettable devices other than the thermal protective devices addressed by this clause are used These devices typically operate at temperatures lower than the operating temperature of the thermal protective device
NOTE 2 It is not a requirement of this standard that conformity to the manufacturer`s specification of the resettable thermal protective device needs to be verified
Protective devices integral with the “m” equipment shall be of the enclosed type such that no compound can enter during the encapsulation process
The suitability of the protective device for encapsulation shall be confirmed either by: a) a documentation from the manufacturer of the device; or b) testing of samples according 8.2.8
NOTE Devices in glass, plastic, ceramic or otherwise sealed are regarded as enclosed types
When required by 5.3.1 the test shall be carried out on samples of the compound(s) used in
Three dry samples of the compound will be tested using "m" equipment Each sample will be circular, measuring 50 mm ± 1 mm in diameter and 3 mm ± 0.2 mm in thickness The samples will be weighed and then immersed in water at a temperature of 23 °C ± 2 K for a minimum of 24 hours.
They shall then be taken out of the water, wiped dry and weighed again within 1 minute The increase in mass shall not exceed 1 %
It is not required to use distilled water for this test.
The sample shall be circular with a diameter of 50 mm ± 1 mm and a thickness of
3 mm ± 0,2 mm The sample shall be symmetrically placed between electrodes 30 mm ± 1 mm in diameter, within a temperature controlled oven, set to achieve the maximum service temperature of the compound
A voltage of 4 kV r.m.s + 5 0 % and with frequency between 48 Hz and 62 Hz shall be applied for not less than 5 min No flashover or breakdown shall occur during the test
The test sequence and number of samples are given in Annex B.
Maximum temperature
A sample of "m" equipment must undergo a type test to verify that the temperature limits outlined in section 6.1 are maintained during normal operation Additionally, for protection levels "ma" and "mb," it is essential to ensure that the maximum surface temperature does not exceed specified limits under fault conditions as defined in section 7.2.1.
For “m” equipment without an external load, the test shall be carried out in accordance with the temperature measurements of IEC 60079-0 taking into account the supply conditions given in 4.4
For “m” equipment with an external load, the test shall be carried out for level of protection
To ensure optimal performance, adjust the current for "ma" and "mb" to the maximum level that does not trigger the protective device Additionally, maintain the protection level "mc" according to the specified load parameters during normal operation and under anticipated regular occurrences.
For equipment classified with a level of protection "ma" and designed for EPL "Da," the maximum surface temperature must be established according to the manufacturer's guidelines, ensuring the equipment is surrounded by a dust layer of at least 200 mm on all sides The final temperature is deemed to be achieved when the temperature increase does not surpass 1 K over a 24-hour period.
Testing, simulation, and analysis are essential for ensuring that equipment meets temperature limitations during malfunction conditions, particularly for systems with non-linear external loads, input power control, or complex failure modes.
Thermal endurance test
The test will be conducted following IEC 60079-0 standards The reference service temperature for the test will be determined by either: a) adding 20 K to the maximum surface temperature of the test sample during normal operation, or b) using the maximum temperature at the component surface within the compound during normal operation, as outlined in section 6.2.2.
The test shall be carried out in accordance with IEC 60079-0
The temperature to be used as the reference service temperature for the test shall be the maximum surface temperature under normal operation, see 6.2.1
The test shall be carried out in accordance with IEC 60079-0
After each test, a visual inspection of the sample is required to ensure there is no visible damage that could compromise its protective qualities This includes checking for cracks, exposure of encapsulated components, adhesion failure, unacceptable shrinkage, discoloration, swelling, decomposition, or softening However, some surface discoloration, such as oxidation in epoxy resin, is acceptable.
In addition, any electrical protective device on which safety depends, other than thermal fuses, shall be verified as remaining functional.
Dielectric strength test
The test will be conducted on various circuit arrangements, including: a) between galvanically isolated circuits; b) between each circuit and all earthed components; and c) between each circuit and the surface of the compound or non-metallic enclosure, which may be covered with conductive foil if required.
In arrangement a), the voltage U required is the total of the rated voltages from both circuits under test Conversely, for arrangements b) and c), the voltage U needed corresponds to the rated voltage of the individual circuit being tested.
For arrangement b), circuits that contain transient suppression components connected between the circuit and the earthed parts, a special test sample without these components shall be permitted for the type test
Dielectric strength shall be verified by test:
• either as given in a relevant industrial standard for the individual items of electrical equipment or,
The test voltage must be gradually increased over a minimum duration of 10 seconds until it reaches the specified level, and this voltage should be sustained for at least 60 seconds without any occurrence of dielectric breakdown.
1) For equipment where the voltage U does not exceed 90 V peak, the test voltage shall be
500 V r.m.s ( + 5 0 %) at 48 Hz to 62 Hz Alternatively, the test voltage shall be 700 V d.c ( + 5 0 %)
2) For equipment where the voltage U exceeds 90 V peak, the test voltage shall be 2U +
1 000 V r.m.s ( + 5 0 %), with a minimum of 1 500 V r.m.s at 48 Hz to 62 Hz Alternatively, the test voltage shall be 2U + 1 400 V d.c ( + 5 0 %) with a minimum of 2 100 V d.c
The test voltage shall be increased steadily within a period of not less than 10 s until it reaches the prescribed value, and it shall then be maintained for at least 60 s
NOTE 1 In the case of equipment that, for electro-magnetic compatibility reasons, contain components connected to the enclosure for the suppression of interference pulses and which could be damaged during the tests, a partial discharge test is sometimes used as an alternative
NOT 2 If the circuit under test is not accessible from the exterior it is possible to prepare a specific test sample with additional connections
The test shall be deemed as passed if no breakdown or arcing occurs during testing
NOTE Typically the current flowing during the test will not exceed 5 mA r.m.s
Cable pull test
The test shall be carried out on one sample, previously unstressed and at 21 °C ± 2 °C
In addition, any electrical protective device on which safety depends, other than thermal fuses, shall be verified as remaining functional
The test will be conducted on various circuit arrangements, including: a) between galvanically isolated circuits; b) between each circuit and all earthed components; and c) between each circuit and the surface of the compound or non-metallic enclosure, which may be covered with conductive foil if required.
In arrangement a), the voltage U required is the total of the rated voltages from both circuits under test Conversely, for arrangements b) and c), the voltage U needed corresponds to the rated voltage of the individual circuit being tested.
For arrangement b), circuits that contain transient suppression components connected between the circuit and the earthed parts, a special test sample without these components shall be permitted for the type test
Dielectric strength shall be verified by test:
• either as given in a relevant industrial standard for the individual items of electrical equipment or,
The test voltage must be applied steadily over a minimum duration of 10 seconds until it reaches the specified value, and it should be maintained for at least 60 seconds without any occurrence of dielectric breakdown.
1) For equipment where the voltage U does not exceed 90 V peak, the test voltage shall be
500 V r.m.s ( + 5 0 %) at 48 Hz to 62 Hz Alternatively, the test voltage shall be 700 V d.c
2) For equipment where the voltage U exceeds 90 V peak, the test voltage shall be 2U +
1 000 V r.m.s ( + 5 0 %), with a minimum of 1 500 V r.m.s at 48 Hz to 62 Hz Alternatively, the test voltage shall be 2U + 1 400 V d.c ( + 5 0 %) with a minimum of 2 100 V d.c
The test voltage shall be increased steadily within a period of not less than 10 s until it reaches the prescribed value, and it shall then be maintained for at least 60 s
NOTE 1 In the case of equipment that, for electro-magnetic compatibility reasons, contain components connected to the enclosure for the suppression of interference pulses and which could be damaged during the tests, a partial discharge test is sometimes used as an alternative
NOT 2 If the circuit under test is not accessible from the exterior it is possible to prepare a specific test sample with additional connections
The test shall be deemed as passed if no breakdown or arcing occurs during testing
NOTE Typically the current flowing during the test will not exceed 5 mA r.m.s
The test shall be carried out on one sample, previously unstressed and at 21 °C ± 2 °C
A further test sample shall be subjected to the cable pull test after conditioning according to 8.2.3.1 at the maximum temperature at the cable entry point
The tensile force applied must be the lesser of 20 times the cable diameter in millimeters or 5 times the mass of the equipment in kilograms For permanent installations, this force can be reduced to 25% of the required value The minimum tensile force is set at 1 N, with a minimum application duration of 1 hour, and the force should be applied in the least favorable direction.
Following testing, the sample must undergo a visual inspection to ensure there is no visible displacement of the cable that could compromise its protective type Additionally, there should be no damage to the compound or cable, such as cracks, exposure of encapsulated components, or adhesion failure, that could impair protection.
Pressure test for Group I and Group II electrical equipment
For level of protection "ma," individual free spaces ranging from 1 cm³ to 10 cm³ require the preparation of two test samples with a pressure connection Similarly, for level of protection "mb," individual free spaces between 10 cm³ and 100 cm³ also necessitate two test samples If multiple free spaces of a size that requires testing are present, the pressure test must be conducted simultaneously across all such spaces.
The pressure test shall be carried out on samples that have already been submitted to the thermal endurance tests (see 8.2.3)
The test shall be carried out with a pressure as shown in Table 6 applied for at least 10 s
Minimum ambient temperature °C Test pressure kPa
≥ –60 1 620 a) This covers equipment designed for the standard ambient temperature range specified in IEC 60079-0
For components with a free space of up to 100 cm³, if they successfully pass the Leakage test on sealed devices as outlined in IEC 60079-15—without the need for conditioning, voltage, or dielectric withstand testing—they can be encapsulated without the necessity of a pressure test.
After testing, a visual inspection of the samples is required to ensure there is no compound damage, such as cracks, exposure of encapsulated components, or adhesion failure, which could compromise protection Additionally, for constructions allowed to have no compound thickness between a free space and a non-metallic enclosure wall, the non-metallic enclosure wall(s) must also show no signs of damage.
Test for resettable thermal protective device
8.2.7.1 Resettable thermal protective devices with switching contacts
The function of the protective device shall be verified This test shall be performed after the thermal endurance test The device shall be capable switching its rated current ≥ 5 000 times
The test shall be deemed as passed if the protective device acts correctly after the test in the range specified in its datasheet
8.2.7.2 Resettable thermal protective devices without switching contacts
The protective device's functionality must be verified following the thermal endurance test It should be capable of limiting the temperature rise, either directly or indirectly, for at least 500 cycles.
The test shall be deemed as passed if the protective device acts correctly after the test in the range specified in its datasheet.
Sealing test for built-in protective devices
The test is to be performed on five samples With the test samples at an initial temperature of
The devices are tested by immersing them in water at a temperature of (50 ± 2) °C for at least 1 minute, ensuring a depth of no less than 25 mm They are deemed satisfactory if no bubbles appear during this test Additionally, an alternative method involves examining five samples post-encapsulation to confirm that the compound has not penetrated the interior.