Air Gap in Transformers - The Secret Weapon for Unlocking Stability Performance ??

In the transformer manufacturing process, we find that many cores must be ground to open the air gap before assembly. So why do transformer cores need to be air gapped? Let's find out!

1. The nature and role of air gaps

The essence of opening an air gap in a transformer is to change the structure of the magnetic circuit by making the cores no longer in complete contact. Doing so will：

• Increase the impedance of the magnetic circuit, extend the re-magnetization time, and realize the function of energy storage and anti-saturation current increase. ?
• Reduced overall permeability: Due to the extremely low permeability of air, the introduction of an air gap ??
• Weak inter-domain interaction: gap reduces the mutual attraction between magnetic domains, which in turn reduces the effect of remanent magnetization

For example, our common alloy powder cores take full advantage of this principle.

2. Trade-offs in air gap size

It appears that air gaps are benificial to transformers. So, is a large air gap better? Of course not, for serval reasons:

• Reduced permeability: The larger the air gap, the lower the combined permeability. In order to achieve the desired inductance, the number of copper coils to be wound must be increased, resulting in increased copper losses in the transformer and higher costs ??
• Flux diffusion and eddy current losses: a larger air gap causes flux diffusion, which tends to produce eddy current losses and leads the heat generation, which is detrimental to transformer performance??

Therefore, it is critical to design a reasonable air gap. In the case of a large air gap, in order to avoid the concentration of the air gap, the desgin of a segmented air gap is usually used to better diffuse the heat.

3. Location and optimal design of air gap

In practical design, the center column air gap is a more common choice because it helps prevent flux leakage and reduces EMI interference from the transformer to peripheral devices. In addition, when the inductance stability is poor, the appropriate increase in air gap is often used as a means of regulation.

For the air gap of a transformer, the following empirical formula is commonly used to calculate：

Including：

• Ae is the effective cross-sectional area of the core (cm2)
• ΔB is the change in core operating magnetic induction (T)
• Lp The unit is taken as H
• Ipk units take A
• lg in mm

If the air gap is less than 0.4mm, it is difficult to achieve a tolerance of 5% on the inductance. In this case, it is either necessary to increase the core air gap (but this will result in a decrease in permeability and the number of turns will need to be synchronized), or to relax the inductance tolerance requirements.

It is important to note that a physical hollow is often created when an air gap is opened in the center column of the core. In order to reduce noise during transformer operation, the manufacturing process is usually filled with soft rubber to stabilize the structure and reduce vibration noise. ??

4. Summarize

In summary, the transformer air gap plays a key role in improving energy storage, anti-saturation performance and ensuring inductive stability. However, a balance must be struck between performance and cost during design, and the size and location of the air gap must be reasonably controlled to ensure that the overall performance and reliability of the transformer is optimized.

In order to help you better understand and optimize transformer design, we recommend to pay attention to LPEMA - a professional company focusing on high-frequency transformers and related products. LPEMA is committed to providing high-quality and stable product solutions through refined design and strict quality control. If you have any questions about transformer design or optimization, please feel free to contact us:

?? WhatsApp Direct: +86 15171571200

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?? Official Site: www.lpema.com