The coil is usually composed of skeleton, winding, magnetic core and shielding cover. According to the different use occasions, some coils have no shielding cover, some have no magnetic core, and others have no fixed frame, only windings.

1. Framework

      The commonly used materials of the skeleton are ceramics, plastics, bakelite and electrical paperboard. The material of the skeleton has a certain influence on the quality and stability of the coil, which is generally selected according to the working conditions.

2. Winding

      Most windings are made of insulated wires wound on the coil skeleton. The insulated wires are commonly used as enamelled wires and electromagnetic wires of various specifications. Generally speaking, the larger the inductance required by the winding, the more the number of coils. The diameter of the selected conductor shall be determined according to the current passing through the winding and the Q value of the coil. When the current passing through is large, the Q value is required to be high, and the diameter of the coil conductor should be selected thicker. When the inductance is less than a few microns, the windings are usually wound with bare silver plated copper coins to reduce the surface resistance of the wire and improve the performance of the coil.

3. Shield

      In order to reduce the influence of external electromagnetic field on the coil and the contribution of electromagnetic field generated by the coil to the external circuit, the coil is often enclosed in the structure with a metal cover and reliably grounded to meet the requirements of isolation from the external circuit.

4. Magnetic core

      After the coil is installed into the magnetic core, the inductance of the coil can be increased, or the number of coils with magnetic core can be reduced compared with the coil without magnetic core with the same inductance, which can reduce the volume and distributed capacitance of the coil, and also improve the Q value of the coil. Sometimes, the inductance of the coil can be adjusted by adjusting the position of the magnetic core in the coil. The magnetic core is usually made of manganese zinc ferrite or nickel zinc ferrite magnetic materials, which can be made into various shapes according to different requirements