What are the requirements for solder joints when winding transformers?

In the winding process, the quality of solder joints is directly related to the performance and reliability of the entire winding assembly. Appropriate welding methods and strict requirements for solder joints are the key factors to ensure the stable electrical performance, sufficient mechanical strength, and long-term safe operation of winding products. The relevant requirements for solder joints include the following

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● Selection of welding methods

For flat copper wires with a thickness less than 1.7 mm, lap welding is adopted. The lapped part is filed into a wedge shape and welded with silver-copper welding rods containing 15% silver. This welding method is suitable for thinner flat copper wires. The silver-copper welding rods can improve the resistivity at the welding joints, making the current conduction more stable. It is commonly used in some small winding devices with high requirements for electrical conductivity and connection strength, such as the small transformer windings in precision electronic instruments. For flat copper wires with a thickness greater than 1.7 mm, butt welding is used.

But welding can better ensure the firmness and integrity of the connection of thicker wires. It is widely used in winding scenarios with large current and high voltage, such as the windings of large power transformers, and can effectively carry larger current loads and reduce heat generation and losses caused by poor connections.

● Basic requirements for welding quality

● Firmness, tightness and surface treatment: The welding  joints should be firm and tight. This is the key to ensuring that the winding will not become loose or break when subjected to mechanical stresses (such as vibration, tension, etc.). Smoothing and sanding the joints can avoid local electric field concentration or the impact on the tight arrangement of the winding due to the unevenness of the joints.

● Position restrictions:The solder joints should not be located at transposition positions or in comb teeth areas. The transposition positions and comb teeth areas are relatively critical and structurally complex regions in the winding. Solder joints in these areas are likely to damage the original electric field distribution and mechanical structural integrity, increasing the risks of partial discharge and mechanical damage. In the winding of high-voltage windings, these requirements must be strictly followed to maintain the uniformity of the electric field inside the winding and its mechanical stability, and to improve the insulation performance and short-circuit resistance.

● Specifications for welding multiple wires

●Offset of welding positions: The welding of multiple wires should be offset from each other, with an offset distance of more than 80 mm. This can avoid problems such as local overheating and magnetic field interference caused by the concentration of multiple welding joints, making the current distribution more uniform.

●Quantity and position restrictions: When multiple wires are wound in parallel, each wire should have no more than one welding joint, and the number of welded wires is strictly limited, and the joints should be offset. This can prevent excessive welding joints from weakening the overall strength and electrical conductivity of the wires and ensure the consistency and reliability of the winding. It must be followed in all kinds of winding designs with multiple wires wound in parallel, such as some special high-frequency transformers or occasions with high requirements for winding uniformity.

● Cleaning requirements

During the welding process, no copper chips or aluminum chips are allowed to fall into the winding. Copper chips may cause short circuits in the winding, damage the insulation, and affect the electrical performance and safety of the winding. In all winding operation environments, strict control must be exercised. Whether it is the winding of small electronic devices or large power equipment, it is necessary to ensure that the working area is clean and prevent foreign objects from mixing in.

In Summary

The requirements for solder joints in winding involve multiple aspects such as welding methods, quality, position, and cleaning. These requirements are formulated based on ensuring the electrical performance, mechanical strength, and operational safety of winding products. In different winding application fields, from precision electronics to large power equipment, strictly following the requirements for solder joints plays an indispensable role in improving product quality and reliability.

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LuShan, est.1975, is a Chinese professional manufacturer specializing in power transformers and reactors for 49 years. Leading products are single-phase transformer, three-phase isolation transformers,electrical transformer,distribution transformer, step down and step up transformer, low voltage transformer, high voltage transformer, control transformer, toroidal transformer, R-core transformer;DC inductors, AC reactors, filtering reactor, line and load reactor, chokes, filtering reactor, and intermediate,high-frequency products.

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