Composition of a Switch Mode Power Supply Transformer
The main materials of switch power transformers are magnetic materials, wire materials, and insulation materials, which are the core of switch transformers
Magnetic materials: The magnetic materials used in switch transformers are soft magnetic ferrite, which can be divided into two categories based on their composition and application frequency: MnZn series and NiZn series. The former has high magnetic permeability and high saturation magnetic induction, and has low losses in the mid frequency and low frequency ranges. There are many shapes of magnetic cores, such as EI type, E type, EC type, etc
Wire material - enameled wire: Generally used for winding small electronic transformers, there are two types of enameled wires: high-strength polyester enameled wire (QZ) and polyurethane enameled wire (QA). According to the thickness of the paint layer, they are divided into two types: type 1 (thin paint type) and type 2 (thick paint type). The insulation coating of the former is polyester paint, which has superior heat resistance and an insulation electrical strength of up to 60kv/mm; The insulation layer of the latter is polyurethane paint, which has strong self adhesion and self welding performance (380 ℃), and can be directly welded without removing the paint film
Pressure sensitive tape: Insulation tape has high electrical strength, is easy to use, and has good mechanical properties. It is widely used in the interlayer, inter group insulation, and outer insulation of switch transformer coils. It must meet the following requirements: good adhesion, anti peeling, certain tensile strength, good insulation performance, good voltage resistance, flame retardancy, and high temperature resistance
Skeleton material: The switch transformer skeleton is different from the general transformer skeleton. In addition to serving as the insulation and support material for the coil, it also undertakes the installation, fixation, and positioning of the entire transformer. Therefore, the material used to make the skeleton should not only meet the insulation requirements, but also have considerable tensile strength. At the same time, in order to withstand the welding heat of the pins, the thermal deformation temperature of the skeleton material is required to be higher than 200 ℃. The material must be flame-retardant and have good processability, making it easy to process into various shapes
