Analysis of the conditions of use of the high-frequency power transformer and design principles

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According to the conditions of use of the high-frequency power transformer (transformer manufacturers) analysis, the overall two-fold: the feasibility and electromagnetic compatibility. Only pay attention to the feasibility of environmental protection awareness, must pay attention to electromagnetic compatibility.

Feasibility refers to the specific conditions of use, high-frequency power transformer can work to life so far. General Conditions of Use of high-frequency power transformer greatest impact is the ambient temperature. Some soft-magnetic material, the Curie point is relatively low, the temperature-sensitive. For example: Mn-Zn ferrite, the Curie point is only 215 ° C, the magnetic flux density, permeability and loss with temperature changes, so in addition to the normal temperature of 25 ° C, but also given 60 ° C, 80 ° C, 100 ° C when the various reference data. Therefore, the Mn-Zn ferrite cores operating temperature is limited to below 100 ° C, it is not because of the optimized design of high-frequency rectifier of class H insulation, can reduce the volume 1/2 to 1/3 the sake of? If yes, please give specific examples of data. The authors have developed the H-class insulation workers frequency 50Hz, 10kVA dry-type transformers, frequency 50 Hz with class B insulation workers, compared to 10kVA dry-type transformers, the volume is reduced by 15% to 20%, has been considerable. Original volume is relatively small high frequency 100kHz10VA high frequency power transformer, such as the secondary winding triple insulated wire, the volume can be reduced by 1/2 to 1/3, it must be a very valuable experience. Please author details to optimize the design, so that readers learn.

Electromagnetic compatibility refers to the high-frequency power transformer neither generate electromagnetic interference from outside, but also to cope with external electromagnetic interference. Electromagnetic interference received, including interference that the audio noise could be heard and can not hear the high-frequency noise. One of the main reasons for the high frequency power transformer electromagnetic interference magnetostriction of the core. Magnetostrictive soft magnetic material, electromagnetic interference generated. For example, the Mn-Zn ferrite magnetostrictive coefficient λS 21 × 10-6, which is more than seven times the grain-oriented silicon steel, high permeability permalloy and amorphous alloys of more than 20 times, microcrystalline nanocrystalline alloy more than 10 times. Therefore, the electromagnetic interference generated by the Mn-Zn ferrite cores. Between the main high frequency power transformer electromagnetic interference as well as core repulsion between the suction and winding wire. These forces change frequency and high-frequency power transformer operating frequency. Therefore, the operating frequency of about 100 kHz high frequency power transformer, no special reason not produce 20kHz audio noise. Since the proposed chip switching power supply 10W audio noise frequency is about 10kHz to 20kHz, must have their reasons. Not shown to the noise spectrum, the specific reasons for that is not clear, but generated by the high-frequency power transformer itself is unlikely, there is no need to glass beads Adhesive bonding core. The only problem with this bonding process to reduce audio noise 5dB, please give examples and data as well as a detailed description of the cause of the noise, will be credible.

Shielded to prevent electromagnetic interference, increased high-frequency power transformer electromagnetic compatibility good way. However, in order to prevent electromagnetic interference propagation of high-frequency power transformer, in the design of the core structure and design of the winding structure should take appropriate measures, only the outer shield is with is not necessarily the best solution, because it can only prevent radiation interference, You can not prevent the conducted interference.

High-frequency power transformer as a product, with the natural attributes of goods, high frequency power transformer design principles and other commodities, under the specific conditions of use specific functions in the pursuit of the best cost performance. Sometimes may emphasis on performance and efficiency, and may sometimes emphasis on price and cost. Now, light, thin, short, small, become the development direction of the high-frequency power, emphasis on reducing costs. High-frequency power transformer, which has become a major difficulty need more efforts in this regard. Therefore, in the high-frequency power transformer design points “, but only the performance, not talk about cost, say that it is a major shortcoming, seriously consider the high-frequency power transformer design principles, the pursuit of better cost performance send less than 10VA chip switching power supply high-frequency transformer should be designed lighter, thin, short, small scheme. Talk about the cost of the law of value in the market is merciless! Many good performance, often due to the price can not be accepted by the market have been left out and eliminated. Often a new product costs veto. Energy-saving money is not festival “Why promotion is not open in the market worth pondering.

Product costs include not only the material costs, production costs, including research and development costs, design costs. Therefore, in order to save time, based on past experience, the high-frequency power transformer iron loss copper loss ratio, the proportion of leakage inductance and magnetizing inductance, the primary and secondary windings loss ratio, current density to provide some reference data, the degree of filling of the window , winding wire and structural recommend some programs, what is wrong? Why must it back and forth a step-by-step estimates and simulation, not only the concept of error? The authors have developed in the mid-1980s, the high-frequency magnetic amplifier switching power supply, the lowest temperature rise conditions, has been optimized for high-frequency power transformer design. Thermal resistance is difficult to determine, a far cry from the results and trial samples had to be corrected again.

In short, do keep in mind: the high-frequency power transformer is a product (three-phase transformer) design principle is to complete a specific function in the specific conditions of use in the pursuit of the best cost performance. The sole criterion for testing the design of the products can be subjected to a live test of the market.

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