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How to choose core when designing switching power transformer
Feb 08, 2018


         How to choose core when designing switching power transformer

When designing a switching power supply transformer, the correct choice of switching power transformer core is a very important process. Only the switching power transformer core is selected, and the switching transformer can achieve good results. So how to choose the core correctly? In fact, all different shapes of magnetic cores have their best application occasions. That is, when choosing to use, raise their length, avoiding them short, and achieve a better design. Before selecting the magnetic core material, first determine the basic parameters of its core material. , That is, according to your specific use of the environment to choose. If it is PC40 or PC50, etc., the size of the output power is mainly to see the size of the magnetic core material cross-sectional area, the number of winding turns and how much the number of windings depends mainly on the core material window area size.

The task of selecting the magnetic core is to determine the material grade and model specification of the transformer core. The common magnetic material used in the switching transformer is a soft ferrite whose composition is MnZn.

Due to differences in formulas and production processes, each company has produced magnetic materials with different specifications of different grades, and provided characteristic parameters for each grade of magnetic materials, such as frequency range of use, initial permeability, specific loss factor, specific temperature coefficient, Saturation magnetic flux density, Curie temperature, resistivity, density, and some parameters with frequency, temperature curve.

The magnetic core is divided into EI, EE, EC, U, UF and other models according to the shape. Each model has a variety of specifications, and each production company also provides the geometry of various model specifications.

The selection of material grades is mainly based on the highest operating frequency of the switching transformer. For example, R2KD is suitable for 30 kHz or less, R2KBD is for 50 kHz or less, and R2KB1 is for 200 kHz or less.

Iron-based amorphous iron core: Highest saturation magnetic induction (1.45 to 1.56 T) in almost all amorphous alloy cores, high magnetic permeability, low coercivity, low loss, low excitation current and good Temperature stability and aging stability. Mainly used to replace silicon steel sheet, as a variety of forms, different power frequency distribution transformers, intermediate frequency transformers, operating frequency from 50Hz to 10KHz; as a high-power switching power supply reactor core, the use of frequency up to 50KHz.

Iron-nickel-based amorphous core: medium-low saturation magnetic induction (0.75T), high magnetic permeability, low coercive force, wear resistance, and good stability. It is often used to replace the permalloy iron core as the zero-sequence current transformer core in earth leakage switches.

Cobalt based amorphous core: Highest magnetic permeability in all amorphous alloy cores, with medium-low saturation magnetic induction (0.65T), low coercive force, low loss, excellent wear resistance And corrosion resistance, good temperature stability and aging stability, shock and vibration resistance.

The above is a summary of how to select the core when designing a switching power supply transformer for everyone, hoping to help everyone. If you want to learn more about the content of high frequency transformers, you can click on the high frequency transformer information.

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