The wires used in transformers are mainly enameled wire, three-layer insulated wire and copper strip.
The so-called enamelled wire is coated with a coating film on the surface of the copper wire, which is commonly used in UEW (polyamine formate enamelled wire), UEW-NY (polyamine formate nylon enamelled wire), PEW (polyester enamelled wire), EIW (polyimine polyester enamelled wire), AIW (polyimine amine enamelled wire).
Among them, UEW and UEW-NY can be directly soldered, and the temperature is often F and H, the difference between the two is that UEW-NY has higher wear resistance, suitable for single-wire multi-coil winding. As far as the thickness of the paint film is concerned, the commonly used daily standards are 1UEW, 2UEW, and 3UEW, and the thickness of the paint film decreases in turn.
To meet the needs of large wire diameters, UEW wire is commonly used to make stranded wire, silk-covered wire, and film-covered wire to reduce skin effect. The advantage of film-coated wire is that it is resistant to high temperature and high pressure, but it needs extra stripping film to solder. The advantage of silk-covered wire is that it can protect the wire during winding and can be soldered directly.
PEW, EIW, and AIW advantages are good wear resistance and scratch resistance, but cannot directly solder, often used to make a variety of inductors. PEW commonly uses temperature grades F and H, and the price is relatively economical. EIW and AIW can withstand temperatures up to 200 degrees Celsius and 220 degrees Celsius and have excellent heat shock and chemical corrosion resistance, which are often used in high-performance products such as flat wire inductors.
Triple-insulated wire refers to the copper softened after the surface processing insulation layer treatment. The first layer is a golden yellow polyamide film, its thickness is several microns, and can withstand 1kV pulse high pressure; The second layer is highly insulating spray paint coating; The third (outermost) layer is a transparent fiberglass layer. In terms of insulation capacity, the damage voltage of the triple insulated wire exceeds 6KV, and some can reach more than 10KV.
At present, the more well-known three-layer insulated wires are TEX-E (FURUKAWA, Japan Furukawa) and TIW-3 (TOTOKU, Japan Tote), and the temperature has B and F levels. One of the values mentioned is that triple insulated wire as an important safety material requires UL certification.
Copper strip refers to the use of copper to develop a certain width and thickness, generally used for high-current winding and transformer shielding. When used as a winding, it can pass a large current, reduce the skin effect and leakage sensation, and usually need to fold the tape to isolate other winding.
Transformer shielding can be divided into internal shielding and external shielding. When used as an internal shield, insulation tape is often used for isolation, and in general, grounding is required. External shielding means that the entire wire is wrapped with copper foil, and the end and end are welded to the magnetic core to reduce the EMI interference of the entire transformer on peripheral devices.