How to identify the quality of the switching DC power transformer?
A switching DC power transformer is a DC power transformer with a switching tube. When designing a DC power supply circuit, in addition to the DC voltage conversion function of ordinary transformers, it also has the functions of insulation and power transmission, and is often used in switching DC power supplies and high-frequency DC power supply equipment.
The DC power transformer, the switching DC transformer and the switching tube together form a self-excited (or other) intermittent oscillator, which modulates the input DC voltage into a high-frequency pulsed DC voltage. The role in energy transmission and conversion In the construction of the flyback DC circuit, the transformer converts electrical energy into magnetic field energy, stores it when the switch is turned on, and releases it when the switch is turned off. In the design of the forward DC power supply circuit, when the switching tube is turned on, the input DC power supply voltage is directly provided to the load, and the energy is stored in the energy storage inductor.
When the switching tube is turned off, the energy storage inductor will conduct freewheeling transmission to the load. The input DC-DC supply voltage is converted to various low voltages required.
The basic configuration of the DC switching transformer is the main material of the DC switching transformer, and the magnetic material, wire material and insulating material are the core of the switching transformer.
Magnetic material: The magnetic material used in switching transformers is soft ferrite, which can be divided into two categories according to its composition and applicable frequency: MnZn and NiZn. The former has high magnetic permeability and high saturation magnetic induction at low and medium levels, and has a loss effect in the low frequency range. Magnetic cores come in various shapes such as EI type, E type, EC type and other wires. Enameled wire: Usually used for winding small electronic transformers. Enameled wire includes high-strength polyester enameled wire (QZ) and polyurethane enameled wire (QA).
According to the thickness of the coating, it can be divided into Type 1 (thin coating type) and Type 2 (thick coating type). The former insulating coating is a heat-resistant polyurethane coating up to 60kV/mm, and the latter insulating layer is a polyurethane coating with strong self-adhesive and self-welding properties (380°C). The pressure-sensitive tape can be directly welded without peeling off the paint film, and the insulating tape has high electric strength.
Due to its ease of use and excellent mechanical properties, it is widely used in switching transformer coils, isolation between groups, and outsourcing isolation. The following requirements must be met: excellent adhesion, peel strength, specific tensile strength, excellent insulation performance and excellent voltage resistance, flame retardancy and heat resistance Skeleton material: The skeleton of a switching transformer is different from that of a general transformer.
It is not only the insulation and support material of the coil, but also plays a role in the installation, fastening and positioning of the entire transformer. Therefore, it is not only necessary to meet the insulation requirements, but also must have considerable tensile strength. At the same time, the welding heat requires the heat distortion temperature of the frame material to be higher than 200°C. The material has flame retardancy, excellent machinability and is easy to process into various shapes.
Classification and parameters of switching DC power transformers Switching DC power transformers are divided into single-excitation switching DC power transformers and double-excitation switching DC power transformers. The functional principles and structures of the two switching DC transformers are different. The input DC power supply voltage of the DC transformer is a unipolar pulse, which is divided into forward and reverse DC power supply voltage outputs. On the other hand, the DC input voltage of a DC transformer with two field switches is a bipolar pulse, usually bipolar. Pulsed DC power supply output voltage.
