1. Wire diameter error; The diameter of the wires used in transformers has a certain manufacturing tolerance, and the linear resistance of the wires is inversely proportional to the square of the wire diameter. Wires with smaller diameters have larger relative errors in diameter, so the range of variation in the DC resistance of the winding is large. A wire with a thicker diameter has a smaller relative error in diameter and a smaller range of variation in the DC resistance of the winding;
2. Using the wrong wire specifications will result in the DC resistance of the winding not meeting the requirements, especially for wires with thinner diameters, which are prone to errors;
3. The tightness of the winding and incorrect turns during winding can also cause changes in the DC resistance;
4. Other factors also affect the internal resistance of the winding, such as whether the solder joints are smooth and free of burrs, temperature, air pressure, and other internal and external conditions;
