EN 61857-31-2017 pdf download.Electrical insulation systems – Procedures for thermal evaluation
– Part 31: Applications with a designed life of 5 000 h or less (IEC 61857-31:2017).
This part of IEC 61857 establishes an EIS evaluation for applications with a designed life of 5 000 h or less. This test method follows the procedures of IEC 60505 and is modified based on the range of designed life.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
IEC 60505, Evaluation and qualification of electrical insulation systems
IEC 61857-1, Electrical insulation systems — Procedures for thermal evaluation — Part 1:
General requirements — Low-voltage
IEC TR 61857-2, Electrical insulation systems — Procedures for thermal evaluation — Part 2:
Selection of the appropriate test method for evaluation and classification of electrical insulation systems
I E C 61857-21, Electrical insulation systems — Procedures for thermal evaluation — Part 21:
Specific requirements for general-purpose models — Wire-wound applications
IEC 61857-22, Electrical insulation systems — Procedures for thermal evaluation — Part 22:
Specific requirements for encapsulated-coil model — Wire-wound electrical insulation system
(EIS)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 61857-1 and the following apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
4 EIS evaluation
Procedure A (see Clause 6) is intended for EIS with a designed life of 1 500 h or less. subjecting one set of test objects to one-temperature ageing at 10 K above the maximum design temperature. The average life of the set under evaluation shall be at least 1 500 h.
Procedure B (see Clause 6) is intended for EIS with a designed life of 5 000 h or less. subjecting one set of test objects to one-temperature ageing at 10 K above the maximum design temperature. The ageing time in Procedure A may be increased up to 5 000 h to correspond to the designed life of the EIS. The average life of the set under evaluation shall be at least 1 500 h.
Procedure C (see Clause 6) is intended for EIS with a designed life of 5 000 h or less, subjecting two sets of test objects to two-temperature ageing at 20 K to 30 K and 30 K to 35 K above the maximum design temperature.
The test results determined by either Procedure A, Procedure B or Procedure C described in Clause 6 can be expanded to larger full thermal evaluations in accordance with IEC 61857 (all parts), if the additional thermal ageing is started prior to the completion of the thermal ageing according to this document. When expanded to a full thermal ageing, the work undertaken according to this document is referred to as a screening test portion of the full thermal ageing. Also, IEC 61857-1 and IEC TR 61857-2 may require a reference EIS to be included in the evaluation for establishing a relative thermal endurance (RTE) rating. When expansion Is needed, an evaluation with regard to other applications shall require the addition of a reference EIS in accordance with an EIS method selected from IEC TR 6 1857-2.
5 Test objects
The test objects and test equipment shall be in accordance with the appropriate test method selected from IEC TR 61857-2.
6 Test procedures
6.1 Procedure A: Establishing a TE for applications with a designed life of 1 500 h or less: one-temperature ageing
Follow the procedures of the selected test method. For the selected test method, one test cycle consists of:
— thermal ageing subcycle according to IEC 60505,
— conditioning subcycle according to IEC TR 61857-2. for example IEC 61857-21 or IEC 61857-22, and
NOTE 168 hours (one week) is used lot accumulating more than 1 500 agoing hours in nine ageing cycles.
If the set of test objects exceeds the original test time of 1 500 h the test may be terminated as the target was achieved or the thermal ageirtg may be continued to achieve an expanded goal.
6.2 Procedure B: Establishing a TE rating for applications with a designed life of
5 000 h or less: one-temperature ageing
The one-temperature ageing described in Procedure A can be extended to accumulate additional hours. The set undergoing thermal evaluation under Procedure A can be extended to a time coordinate of up to 5 000 h.
6.3 Procedure C: Establishing a TE rating for applications with a designed life of
5 000 h or less: two-temperature ageing
For these two-temperature ageing applications, the recommendation is for two sets of the candidate EIS test objects to undergo test cycles at each of two elevated ageing temperatures. One test cycle consists of
— thermal ageing subcycle according to IEC 60505,
— conditioning subcycle. and
— diagnostic testing in accordance with the procedures of the test method selected from IEC TR 61857-2 with the following selected ageing temperatures:
• the lower temperature shall be 20 K to 30 K above the expected thermal class value, and
• the higher ageing temperature shall be 30 K to 35 K above the expected thermal class value.
7 Data analysis
7.1 Analysis — Test Procedures A and B (See 6.1 and 6.2)
The thermal classification is evaluated and established when there are no failed test objects and no breakdown of the EIS prior to accumulating the specific number of hours. No projection is needed or made with the accumulated single data point. The application expected life is reached prior to the failure of the EIS undergoing the thermal ageing exposure.
If any specimens have a failure of the EIS prior to accumulation of the selected number of hours, the TE shall be established by using the average life (AL) of the set of test objects. The AL Is calculated in accordance with the procedure given in IEC 61857-1.EN 61857-31-2017 pdf download.