1.1本试验方法包括在大气压力下测定薄膜绝缘圆形磁铁线在空气中的耐热性。它不适用于纤维绝缘的磁性导线，如棉花或玻璃。 1.2本试验方法包括通过观察交流耐压试验响应的变化来评估耐热性。通过观察磁线绝缘的其他特性的变化来评估耐热性，需要使用不同的测试方法。 1.3在没有空气的情况下，将某些类型的薄膜绝缘导线暴露在气体或液体环境中进行加热，可能会产生不同于在空气中获得的耐热性值。当解释在使用中电线不会暴露于空气中的应用中通过空气加热获得的结果时，请考虑这种可能性。 1.4在超过甚至接近放电起始电压的水平下长时间施加的电应力可能会显著改变薄膜绝缘导线的耐热性。在这种电应力条件下，材料之间的比较也可能不同于使用该方法进行的比较。 1.5本试验方法类似于IEC 60172 . 试样制备方面存在差异。 1.6以英寸-磅为单位的数值应视为标准值。括号中的国际单位仅供参考。 1.7 本标准并非旨在解决与其使用相关的所有安全问题（如有）。本标准的用户有责任在使用前制定适当的安全和健康实践，并确定监管限制的适用性。 ====意义和用途====== 5.1本试验方法有助于测定薄膜绝缘圆磁线在空气中的耐热特性和热指数（见 1.3 )（见试验方法 D3251 ). 在对更复杂的系统进行测试或功能评估之前，该测试方法用作筛选测试。它还用于无法进行完整功能系统测试的情况。 5.2经验表明，薄膜绝缘电线和电绝缘清漆或树脂在热暴露过程中会相互影响。试验方法 D3251 提供绝缘清漆或树脂和薄膜绝缘导线组合的耐热性指示。与不含清漆的膜绝缘导线的寿命相比，清漆或树脂与膜绝缘之间的相互作用可能会增加或减少清漆和膜绝缘导线组合的相对热寿命。 5.3导线类型或导线表面状况将影响薄膜绝缘磁线的耐热性。本试验方法用于确定各种导体上薄膜绝缘的耐热特性。使用不同于中规定的尺寸 7.1.1 允许，但不建议用于确定耐热特性。 5.4本试验方法确定的温度指数是20℃时的标称值或相对值，单位为摄氏度 000 h。它仅用于比较目的，不代表薄膜绝缘导线可操作的温度。 5.5有许多因素会影响使用本试验方法获得的结果。其中较为明显的是: 5.5.1导线尺寸和膜厚度。 5.5.2验证电压试验期间的潮湿条件。 5.5.3烘箱结构: 5.5.3.1空气流速。 5.5.3.2置换空气量。 5.5.3.3消除热暴露期间的分解产物。 5.5.3.4烘箱装载。 5.5.3.5烘箱保持温度的精度。 5.5.4在大多数实验室中，耐热烘箱的数量有限，因此，许多不同的试样组在同一烘箱中热暴露。每次打开烤箱时，不一定要取出所有样本。这种额外的温度循环可能会产生退化影响。 5.5.5小心处理试样，尤其是在绝缘变脆的后一个循环中。 5.5.6在随后的热耐久性循环中，试样的振动将产生劣化效应。 5.5.7介电测试仪器的电气特性。提到 8.4 和 8.5 . 5.5.8环境因素，如水分、化学污染和机械应力或振动，是在薄膜绝缘导线因热劣化而减弱后可能导致故障的因素，在绝缘系统测试中进行更合适的评估。

1.1 This test method covers determination of the thermal endurance of film-insulated round magnet wire in air at atmospheric pressure. It is not applicable to magnet wire with fibrous insulation, such as cotton or glass. 1.2 This test method covers the evaluation of thermal endurance by observing changes in response to ac proof voltage tests. The evaluation of thermal endurance by observing changes in other properties of magnet wire insulation requires the use of different test methods. 1.3 It is possible that exposure of some types of film insulated wire to heat in gaseous or liquid environments in the absence of air will give thermal endurance values different from those obtained in air. Consider this possibility when interpreting the results obtained by heating in air with respect to applications where the wire will not be exposed to air in service. 1.4 It is possible that electric stress applied for extended periods at a level exceeding or even approaching the discharge inception voltage will change significantly the thermal endurance of film insulated wires. Under such electric stress conditions, it is possible that comparisons between materials will also differ from those developed using this method. 1.5 This test method is similar to IEC 60172 . Differences exist regarding specimen preparation. 1.6 The values stated in inch-pound units are to be regarded as the standard. The SI units in parentheses are provided for information only. 1.7 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. ====== Significance And Use ====== 5.1 This test method is useful in determining the thermal endurance characteristics and thermal indices of film-insulated round magnet wire in air (see 1.3 ) (see Test Method D3251 ). This test method is used as a screening test before making tests of more complex systems or functional evaluation. It is also used where complete functional systems testing is not feasible. 5.2 Experience has shown that film-insulated wire and electrical insulating varnishes or resins can affect one another during the thermal exposure process. Test Method D3251 provides indications on the thermal endurance for a combination of insulating varnish or resin and film insulated wire. It is possible that interaction between varnish or resin and film insulation will increase or decrease the relative thermal life of the varnish and film insulated wire combination compared with the life of the film insulated wire tested without varnish. 5.3 The conductor type or the surface condition of the conductor will affect the thermal endurance of film-insulated magnet wire. This test method is used to determine the thermal endurance characteristics of film insulation on various kinds of conductors. The use of sizes other than those specified in 7.1.1 is permissible but is not recommended for determining thermal endurance characteristics. 5.4 The temperature index determined by this test method is a nominal or relative value expressed in degrees Celsius at 20 000 h. It is to be used for comparison purposes only and is not intended to represent the temperature at which the film insulated wire could be operated. 5.5 There are many factors that influence the results obtained with this test method. Among the more obvious are the following: 5.5.1 Wire size and film thickness. 5.5.2 Moisture conditions during proof voltage tests. 5.5.3 Oven construction: 5.5.3.1 Velocity of air. 5.5.3.2 Amount of replacement air. 5.5.3.3 Elimination of products of decomposition during thermal exposure. 5.5.3.4 Oven loading. 5.5.3.5 Accuracy with which the oven maintains temperature. 5.5.4 In most laboratories, the number of thermal endurance ovens is limited and, therefore, many different sets of specimens are thermally exposed in the same oven. All specimens are not necessarily removed each time the oven is opened. This extra temperature cycling will possibly have a degrading influence. 5.5.5 Care with which specimens are handled, especially during latter cycles when the insulation becomes brittle. 5.5.6 Vibration of specimens will have a degrading effect during the later thermal endurance cycles. 5.5.7 Electrical characteristics of dielectric test instrument. Refer to 8.4 and 8.5 . 5.5.8 Environmental factors such as moisture, chemical contamination, and mechanical stresses, or vibration are factors that will possibly result in failure after the film insulated wire has been weakened by thermal deterioration and are more appropriately evaluated in insulation system tests.