Your reliable partner in electrical testing & measurement since 1983
Yoanpower is the international trade brand and export subsidiary of Wuhan Defu Electric Co., Ltd. (武汉市得福电气有限公司), a high-tech enterprise founded in 1983, specializing in the R&D and manufacturing of high voltage test transformers and electrical test equipment.
For four decades Defu Electric has served power generation, transmission and distribution utilities, research institutes and electrical equipment manufacturers with advanced HV testing instruments. Recognized as a technology enterprise by the Wuhan Municipal Science & Technology Commission, we maintain long-term cooperation with Wuhan University of Science and Technology, Huazhong University of Science and Technology (HUST) and the Wuhan High Voltage Research Institute, with professors supervising production throughout the process.
In 2001, the National Development and Reform Commission (NDRC) and the Wuhan High Voltage Research Institute appointed us as a drafting member of China's power industry standards — the only manufacturing enterprise in Wuhan to hold this role. We participated in drafting DL/T 848.2-2004 (Power-frequency HV test devices), DL/T 848.3-2004 (Partial-discharge-free test transformers) and DL/T 848.4-2004 (Three-frequency test transformer devices), and multiple products have won national, provincial and municipal awards.
Our equipment is trusted by Siemens (China), Baosteel, Wuhan Iron & Steel (WISCO), BYD, China Chemical Engineering, and leading power construction companies across China. Through Yoanpower, the same factory-grade quality now reaches utilities and EPC contractors in the USA, India, Nigeria, Southeast Asia and 60+ countries worldwide.
Series resonant AC withstand voltage test — on-site commissioning by our engineers
Wuhan Defu Electric founded — specialized in high voltage test transformers and electrical test equipment.
Developed the lightweight oil-immersed test transformer, setting the foundation for portable HV testing.
Launched the first-generation insulating-oil dielectric strength tester (oil tester), a long-selling core product.
Technical breakthrough — test transformers exceeded 150 kV and high-current generators exceeded 10,000 A.
Put the power-frequency DC high-voltage generator into production, broadening the HV source portfolio.
Appointed by the Wuhan High Voltage Research Institute as a Power Industry Standard Drafting Member — the only manufacturing enterprise in Wuhan to hold this role.
Participated in drafting the national power-industry standard DL/T General Technical Conditions for High-Voltage Test Equipment, issued and implemented by the NDRC.
Put the variable-frequency (AC) series resonant test system into production, expanding the HV withstand-voltage product line.
Our inductive series resonant system was recognized as a designated brand by SEPCO3 (Shandong Electric Power Construction No.3) for overseas power projects.
Comprehensive upgrade of smart products — variable-frequency resonant systems, volt-ampere characteristic testers and microcomputer relay protection testers.
Launched the Yoanpower international trade brand — bringing Defu's 40+ years of factory-grade HV test equipment to utilities and EPC contractors in 60+ countries worldwide.
Business license, ISO 9001:2015, industry standard drafting, patents and more — full scanned copies available on request.
Want the full scanned copies (PDF / high-res)? Visit our Certificates page
