ASTM D3251:19 pdf download

ASTM D3251:2019 pdf download.Standard Test Method for Thermal Endurance Characteristics of Electrical Insulating Varnishes Applied Over Film-lnsulated Magnet Wire.
7. Sampling
7.1 Sample the varnish in accordance with Test Methods
D115.
8. Test Specimen
8.1 Twist two pieces of film-insulated magnet wire in accordance with Table 1 on Tension and Number of Twists for Twisted Pair Construction in Test Method D2307.
8.2 Use the specimen holder described in Test Method
D2307.
8.3 Use one set, consisting of a minimum of ten varnished and ten unvarnished test specimens, for each test temperature (Note 2). Eleven specimens are recommended if calculations are to he in accordance with the median calculation method of Test Method D2307.
NorE 2—If several varnishes are being evaluated, it is necessary to run only one set of unvarnished specimens at each temperature.
9. Procedure
9.1 Condition all specimens 30 to 60 mm at 150 ± 2°C and proof test in accordance with Test Method D2307.
9.2 Coat all of the specimens as follows:
9.2. 1 Solvent Varnishes:
9.2.1.1 Adjust the consistency of solvent based varnishes to give a 0.025 ± 0.0005 mm (0.001 ± 0.0002 in.) build on a 0.127 ± 0.008 mm (0.005 ± 0.0003 in.) copper strip withdrawn at a rate of 90 to 110 mm/mm (3.5 to 4.3 in,/min). Drain for 10 mm and bake according to the supplier’s recommendations. Refer to Test Methods Dl 15 for a more detailed procedure.
9.2. 1 .2 Immerse the specimens in the adjusted varnish, and withdraw them at a rate of approximately 100 mm/mm (4 in./min). Alternately, specimens may be coated by trickling. The specimens are held in a fixture horizontal and the resin is applied along the length of the twisted sectioned and part way tip the legs. Drain for 10 mm and bake in the direction processed and according to the supplier’s recommendations.
9.2.1.3 Reverse the specimens end for end for specimens processed vertically and repeat 9.2.1.2. For horizontally processed specimens, flip specimens over so that the original side up is down and repeat 9.2.1.2.
9.2.2 Solveii tiess Varnishes:
9.2.2.1Test solventless varnishes in the “as made”condi-tion.
9.2.2.2 The number of dips used for a solventless varnish isto be agreed upon between the interested parties. Report thenumber of dips used. If multiple dips are used,reversespecimens end for end before dipping.
9.2.2.3 Process specimens using solventless varnish,asdescribed in 9.2.1.2 and 9.2.1.3.
9.3 Place an equal number of the coated and uncoatedspecimens in the holders as described in Test Method D2307for a direct comparison. In some cases, the thermal character-istics of the magnet wire is well known and testing is notrequired to gain useful comparative data.
9.4 After coating with varnish,proof test all specimens inaccordance with Test Method D2307.The proof voltage isbased on the thickness of the film insulation on the magnet wireand is not dependent on the thickness of the varnish coating.9.5Choose at least three different test temperatures fromTable 3 of Test Method D2307; age one set each of coated anduncoated specimens at each temperature. Choose the exposuretime in accordance with Test Method D2307.
9.6Test the specimens and then age them in accordancewith Test Method D2307.