The Complete Guide Production Process Of High Frequency Transformer

High frequency transformers are an essential component in many electronic devices, especially those that require efficient power transfer, such as power inverters, switch-mode power supplies, and audio equipment. Therefore, it is essential to have a comprehensive understanding of the production process of high frequency transformers to ensure that high-quality transformers are manufactured.

The production process of high frequency transformers typically involves five critical steps: design, material selection, winding, assembly, and testing.

The specific steps are as follows:

Design and Planning

The first step is to create a design plan for the transformer that meets the required specifications. This includes selecting the appropriate core material, wire, insulation, and other materials necessary for the transformer.
When designing and planning a high frequency transformer, the following information needs to be considered:

1. Transformer application: Determine which electronic devices and systems the transformer will be used for, such as power inverters, switch-mode power supplies, and audio equipment.
2. Input and output voltage: Determine the transformer’s input and output voltage. This helps to determine the transformer’s turns ratio.
3. Rated power: Determine the power that the transformer needs to transfer. This helps to determine the transformer’s size and circuit design.
4. Operating frequency: Determine the operating frequency of the transformer. The frequency for high frequency transformers is typically above 10kHz.
5. Electrical performance requirements: Understand the transformer’s electrical performance requirements, such as output voltage stability, temperature coefficient, efficiency, etc.
6. Packaging requirements: Determine the transformer’s packaging form, such as surface mounting or through-hole.
7. Core material: Select the appropriate core material, such as silicon steel or nickel-zinc ferrite.

Core Preparation

The core is the foundation of the transformer, and the preparation process involves cutting and shaping the core material to the required size and shape.

When choosing the size and shape of the magnetic core, the following factors should be considered:

1.Working frequency

Different magnetic core materials and sizes have different permeability and loss characteristics at different frequencies. Therefore, it is necessary to choose the appropriate magnetic core size and shape according to the working frequency of the designed high-frequency transformer.

The determination of the size and shape of a magnetic core based on the operating frequency of a transformer requires consideration of several factors:

1. Selection of magnetic core material: Different magnetic core materials have varying permeability and loss characteristics at different frequencies. Therefore, when selecting a magnetic core, it is necessary to choose a suitable magnetic core material based on the operating frequency of the designed high-frequency transformer. For example, nickel-zinc ferrite (NiZn) is a commonly used magnetic core material in the high-frequency range because it has a higher permeability and lower loss characteristics.
2. Calculation of magnetic core cross-sectional area: The magnetic core cross-sectional area is calculated based on the input voltage, output voltage, and operating frequency of the transformer. According to the transformer turns ratio formula, turns ratio = output voltage / input voltage, the turns ratio of the transformer can be determined. The cross-sectional area of the magnetic core can then be calculated as cross-sectional area = power / (turns ratio × AC magnetic flux density of the magnetic core × operating frequency).
3. Calculation of magnetic core length: The calculation of the magnetic core length also requires consideration of the input voltage, output voltage, and operating frequency of the transformer. The magnetic flux of the magnetic core can be calculated using the formula magnetic flux = magnetic core cross-sectional area × magnetic flux density. Then, the magnetic core length can be calculated based on the transformer power and magnetic flux.
4. Selection of magnetic core shape: The shape of the magnetic core is also selected based on the operating frequency. For example, for high-frequency transformers, a toroidal magnetic core is usually selected because it has low leakage and AC resistance. For low-frequency transformers, a square or rectangular magnetic core may be selected.

2.Rated power

The rated power of the high-frequency transformer is also related to the size and shape of the magnetic core. A larger magnetic core can transmit more power but will also increase the size and weight of the transformer. Here are some common steps and guidelines:

• Determine the magnetic core material and shape: Firstly, it is necessary to select a suitable magnetic core material, such as ferrite, nickel-iron alloy, etc., and determine the shape of the magnetic core, such as toroidal, E-shaped, U-shaped, etc.
• Calculate the magnetic flux density: Based on the rated power and voltage, the rated current of the transformer can be calculated, and then the required magnetic flux density of the transformer can be calculated based on the design frequency and material properties of the transformer.
• Determine the magnetic core size: Based on the shape of the magnetic core and the calculated magnetic flux density, the size of the magnetic core can be determined. Generally, the larger the cross-sectional area of the magnetic core, the higher the efficiency of the transformer, but the cost will also increase accordingly.
• Consider winding design: While determining the size of the magnetic core, the design of the winding also needs to be considered. The diameter of the winding wire and the number of winding layers will both affect the performance and cost of the transformer.

3.Magnetic core material

Different magnetic core materials have different permeability, loss characteristics, and saturation magnetic induction intensity. For example, silicon steel sheets have high permeability and low loss characteristics, which are suitable for low-frequency applications, while nickel-zinc ferrites are suitable for high-frequency applications and have a higher saturation magnetic induction intensity.

When designing a high-frequency transformer, selecting the appropriate magnetic core material has a significant impact on the transformer’s performance and cost. Here are some guidelines for choosing magnetic core materials:

1. Ferrite core: Ferrite core is a commonly used magnetic core material that has high permeability, low loss, and good saturation induction characteristics. Ferrite cores are suitable for high-performance applications such as high-frequency transformers and inductors.
2. Nickel-iron alloy core: Nickel-iron alloy core is a magnetic core material with high saturation induction strength, low temperature drift, and stability. Nickel-iron alloy cores are suitable for high-temperature and high-magnetic-field applications such as high-frequency transformers and magnetic storage devices.
3. Silicon steel core: Silicon steel core is a magnetic core material with low loss and high permeability, typically used in low-frequency transformers and motors.
4. Magnetic stainless steel core: Magnetic stainless steel core is a magnetic core material with high saturation induction strength and low hysteresis loss. Magnetic stainless steel cores are suitable for high-performance applications such as high-frequency transformers and inductors.

4.Magnetic core shape

The shape of the magnetic core also affects the performance of the high-frequency transformer. For example, a rectangular magnetic core shape is suitable for designing smaller high-frequency transformers, while a toroidal magnetic core shape is suitable for designing larger high-frequency transformers. When selecting a magnetic core shape, it is necessary to consider the transformer’s design requirements and application scenarios. The following are several common magnetic core shapes:

• Toroidal core: A toroidal core is a common magnetic core shape used in high-frequency transformers and inductors. Due to its good magnetic circuit closure, it has the characteristics of low leakage and low noise.
• E-type core: An E-type core is a magnetic core shape with two side surfaces and a central waist, suitable for high-frequency transformers and inductors. Due to its larger cross-sectional area, it can achieve higher power density.
• U-type core: A U-type core is a magnetic core shape with two side surfaces and a central waist, suitable for high-frequency transformers and inductors. Due to its smaller leakage inductance and better magnetic circuit closure, it can achieve higher energy efficiency and lower noise.
• RM-type core: An RM-type core is a magnetic core shape with four side surfaces and a central waist, suitable for high-frequency transformers and inductors. Due to its larger cross-sectional area and better magnetic circuit closure, it can achieve higher power density and lower leakage.

When selecting a magnetic core shape, the most suitable shape needs to be determined based on the transformer’s power, frequency, working temperature, and other parameters to ensure that the transformer has good performance and stability.

Winding

This step involves winding the wire around the core to create the primary and secondary coils. The wire must be wound in a precise pattern and direction to ensure proper function of the transformer.

Insulation and Impregnation

Once the coils are wound, they are coated with a layer of insulation to prevent short circuits and improve electrical performance. Additionally, the coils may be impregnated with a resin or varnish to further enhance their durability.

Final Assembly and Testing

Finally, the transformer is assembled and tested to ensure it meets all necessary specifications. This includes testing for electrical performance, temperature resistance, and other factors that may impact the transformer’s functionality.

Overall, the production process of a high frequency transformer requires careful attention to detail and precision to ensure the final product meets the necessary requirements and performs reliably over time.