DIN EN 61857-21:2010
电气绝缘结构.热评定规程.第21部分:通用模式的专门要求.线绕器件(IEC 61857-21-2009).德文版本EN 61857-21-2009
Electrical insulation systems - Procedures for thermal evaluation - Part 21: Specific requirements for general-purpose models - Wire-wound applications (IEC 61857-21:2009); German version EN 61857-21:2009