The manufacturing processes of transformer clamps vary according to their structure and materials.
Stamping forming is a basic process, in which the plate is stamped into the required shape through a die. Stainless steel clamps can be shipped after cleaning and packaging after stamping. For clamps with complex structures, welding processing is required. During welding, parameters must be strictly controlled to ensure the height and fullness of the weld, and to ensure the strength and flatness of the clamps. Surface treatment is indispensable. Processes such as tin plating, galvanizing, and spraying anti-corrosion paint can improve rust resistance, oxidation resistance, and weldability. For example, SK7 clamps need to undergo heat treatment and tin plating to enhance their performance.
Material Innovation and Development of Transformer Clamps
The material development history of transformer clamps is a history of innovation constantly pursuing a balance of "strength, low loss and durability". Traditional Q235 carbon steel, although its yield strength can reach 235MPa and can meet the basic needs of small and medium-sized transformers, in the alternating magnetic field, its magnetic permeability μ is about 800-1000μ₀ (μ₀ is the vacuum magnetic permeability), which is prone to eddy current loss. In 10kV transformers, such loss can account for 3%-5% of the total loss. For this reason, low-magnetic steel has gradually become the preferred material for large transformer clamps. For example, the austenitic stainless steel of model 1Cr18Ni9Ti has a magnetic permeability μ of only 1.02-1.05μ₀, almost close to non-magnetic materials. Clamps made of this material can reduce eddy current loss by more than 90%, especially suitable for transformers with 35kV and above voltage levels.
In recent years, the application of fiber-reinforced polymer (FRP) in small transformer clamps has shown unique advantages. Clamps made of glass fiber and epoxy resin composite have a density of only 2.0-2.2g/cm³, which is about 1/4 of that of steel, which can reduce the overall weight of the transformer by 20%-30%. Moreover, their salt spray resistance exceeds 5000 hours, which is more than 5 times that of traditional galvanized steel, making them very suitable for use in corrosive environments such as chemical industry and coastal areas. However, although the tensile strength of current FRP materials can reach 300-500MPa, close to that of Q235 steel, their elastic modulus is only 20-40GPa, about 1/5 of that of steel. When bearing large loads, the deformation is large. Therefore, they are mostly used in transformers with a capacity below 100kVA, and usually need to be used with metal reinforcing ribs.
The emergence of new alloy steels has further improved the comprehensive performance of clamps. For example, Q460 steel with micro-alloying elements such as vanadium and niobium added, through controlled rolling and controlled cooling process, its yield strength can reach more than 460MPa, and the elongation rate is maintained above 18%. Compared with traditional steel, under the same thickness, its impact resistance is increased by 30%, and it can still maintain good toughness in the low-temperature environment of -40℃, avoiding faults caused by brittle fracture of transformer clamps in cold winter areas.
