Core customization

    Source transformer core performance requirements and material classification

    In order to meet the requirements of switching power supply to improve efficiency and reduce size and weight, a high magnetic flux is required Transformer core with high density and high frequency and low loss. Although there is competition with high-performance amorphous soft magnetic alloys, soft ferrite materials are still the best choice in terms of performance-price ratio; especially in the high-frequency range from 100kHz to 1MHz, new low-loss high-frequency power Ferrite materials have their unique advantages. In order to make the best use of the magnetic core, the soft ferrite material under higher power operating conditions should have the following most important magnetic properties in the high temperature working range (such as 80～100℃):

    1) High saturation magnetic flux density or high amplitude permeability. In this way, the transformer core allows a large magnetic flux deviation at the specified frequency, which can reduce the number of turns; this is also conducive to the high-frequency application of ferrite, because the cut-off frequency is proportional to the saturation magnetic flux density.

    2) There is a low total core loss in the operating frequency range. Under given temperature rise conditions, low core loss will allow high passing power.

    The incidental requirements include high Curie point, high resistivity, and good mechanical strength.

    The newly released “soft ferrite material classification”industry standard (equivalent to IEC61332:1995), the high magnetic flux density application of power ferrite Body materials are divided into five categories, see Table 1. In addition to the requirements for amplitude permeability and power loss, each type of ferrite material also proposes the “performance factor” parameter (this parameter will be further described below). From PW1 to PW5 category, the applicable operating frequency is gradually increased, such as PW1 material, the applicable frequency is 15-100kHz, mainly used in flyback transformer core; PW2 material, the applicable frequency is 25-200kHz, mainly used in switching power supply Transformer core; PW3 material, suitable frequency is 100～300kHz; PW4 material suitable frequency is 300kHz～1MHz; PW5 material suitable frequency is 1～3MHz, domestic production is equivalent to PW1～PW3 material, PW4 material can only be produced in small quantities , PW5 material has yet to be developed.