The general standard governing power transformer cores is GB/T 32288-2020, "Electrical Steel Cores for Power Transformers." This standard serves as the core national benchmark for core production, inspection, and assembly, fully superseding the previous GB/T 32288-2015 version. It establishes unified specifications for material requirements, dimensional tolerances, stacking processes, surface quality, and electromagnetic performance indicators for conventional stacked power transformer cores. It defines loss grades, insulation coating properties, and joint gap control standards for grain-oriented silicon steel sheets, while strictly limiting key parameters such as no-load loss, no-load current, and magnetic flux density. Additionally, it outlines fundamental requirements for structural assembly, fastening methods, and grounding processes. Applicable to the vast majority of oil-immersed and dry-type distribution transformer cores, it serves as the industry-wide guideline for manufacturing and factory acceptance, ensuring consistent product quality and performance compliance.
For cores featuring special structures or materials, the industry employs specific, specialized national standards tailored to diverse operating conditions. Notably, GB/T 32825-2024 is the current standard governing technical parameters, structural requirements, and performance indicators for three-phase dry-type transformers with three-dimensional wound cores; it specifically regulates seamless magnetic circuits, forming precision, operating noise, and loss parameters to suit energy-efficient dry-type transformer applications. Amorphous alloy cores-a category known for high energy efficiency-are subject to dedicated technical standards for dry-type and oil-immersed applications; these standards specify material selection, magnetic stability, vibration resistance, and temperature rise requirements, while strictly controlling low-loss energy efficiency metrics. Furthermore, small cores for electronic equipment adhere to GB/T 4596-2012, which specifies dimensions, tolerances, and testing methods for E-type cores, thereby creating a comprehensive standards framework covering general-purpose, energy-efficient, and small precision cores.
Testing, acceptance, and operation and maintenance of transformer cores strictly adhere to relevant electric power industry standards, ensuring safe and compliant equipment operation. Factory and type tests for iron cores must comply with national standards for general transformer testing, clearly defining the inspection procedures and acceptance criteria for insulation performance, grounding methods, loss measurements, noise levels, and temperature rise. Mandatory requirements dictate the use of a single-point grounding process to eliminate the risks associated with multi-point grounding. The standards strictly define criteria for identifying defects-such as core stacking misalignment, gap deviations, coating damage, deformation, and corrosion-and clearly outline the rules for classifying products as non-compliant. Furthermore, regulations govern the transportation, storage, and assembly environments, mandating protection against moisture, vibration, and deformation. This establishes standardized, end-to-end control-spanning manufacturing, testing, on-site installation, and operation and maintenance-to ensure the long-term stable, compliant, and efficient operation of various transformer iron cores.
