IEC 61788的本部分介绍了一种测定Nb3Sn复合超导体直流临界电流的试验方法，该复合超导体由青铜工艺或内部锡扩散工艺制成，铜/非铜比大于0.2。 本方法适用于在标准试验条件下，在小于或等于上临界磁场0.7倍的磁场下，临界电流小于1000 A且n值大于12的超导体。测试期间，将试样浸入已知温度的液氦浴中。Nb3Sn复合测试导体具有整体结构，总圆形横截面积小于2 mm2。本试验方法中使用的试样几何形状为感应式卷绕试样。 本标准中给出了与本试验方法的偏差，这些偏差允许用于常规试验和其他特定限制。 临界电流超过1000 A或总横截面积大于2 mm2的Nb3Sn导体可以用本方法测量，预计精度会降低，且自场效应更显著（见附录C）。其他更专业的试样测试几何形状可能更适用于更大的导体测试，为了简单和保持精度，本标准省略了这些测试。 本标准中给出的试验方法原则上应适用于通过任何其他工艺制造的Nb3Sn复合线。经过适当的改进后，该方法有望应用于其他超导复合线。

This part of IEC 61788 covers a test method for the determination of the d.c. critical current of Nb3Sn composite superconductors which are fabricated by either the bronze process or the internal tin diffusion process and have a copper/non-copper ratio larger than 0,2. This method is intended for use with superconductors which have critical currents of less than 1 000 A and n-values larger than 12 under standard test conditions and at magnetic fields of less than or equal to 0,7 times the upper critical magnetic field. The test specimen is immersed in a liquid helium bath at a known temperature during testing. The Nb3Sn composite test conductor has a monolithic structure with a total round-cross-sectional area that is less than 2 mm2. The specimen geometry used in this test method is an inductively coiled specimen. Deviations from this test method which are allowed for routine tests and other specific restrictions are given in this standard. Nb3Sn conductors with critical currents above 1 000 A or total cross-sectional areas greater than 2 mm2 can be measured with the present method with an anticipated reduction in precision and a more significant self-field effect (see Annex C). Other, more specialized, specimen test geometries may be more appropriate for larger conductor testing which have been omitted from this present standard for simplicity and to retain precision. The test method given in this standard should in principle apply to Nb3Sn composite wires fabricated by any other process. This method is also expected to apply to other superconducting composite wires after some appropriate modifications.