What is the function of the iron core inside the low-frequency transformer?

1. Constructing magnetic circuit and conducting magnetic flux

The iron core is the main carrier of the magnetic circuit in the low-frequency transformer, responsible for concentrating and guiding the magnetic field to form a closed magnetic flux loop.

(1) Magnetic flux conduction
The iron core efficiently conducts the magnetic lines of force generated by the winding through high magnetic permeability materials, enhances the magnetic field strength, and thus improves the efficiency of power transmission.

(2) Reducing magnetic leakage
The structural design of the iron core (such as ring and C shape) can minimize the air gap in the magnetic circuit and reduce magnetic leakage. For example, the ring iron core has no air gap, extremely low magnetic leakage, and low electrical noise, which is suitable for high-precision scenarios.

2. Reducing energy loss
The material and process of the iron core directly affect the efficiency and temperature rise of the transformer:

(1) Reducing eddy current loss
Silicon steel sheets block the eddy current path through the surface insulation layer lamination process, thereby reducing eddy current loss. For example, the ring iron core wound with cold-rolled silicon steel strip can further optimize the magnetic circuit and reduce lateral eddy current.

(2) Suppressing hysteresis loss
The hysteresis loop of high permeability silicon steel sheets is narrower, and the energy loss during magnetization and demagnetization is smaller.

(3) Heat dissipation optimization
The structural design of the core (such as the layout of the heat sink) combined with the thermal conductivity of the material can improve the heat dissipation efficiency and prevent performance degradation or shortened life due to temperature rise.

3. Supporting mechanical structure and stability

The core is not only the core of the magnetic circuit, but also the physical skeleton of the transformer:

(1) Mechanical support
The core provides rigid support for the winding coil to ensure the stability of the coil under the action of electromagnetic force. For example, the laminated structure of the laminated silicon steel sheet can enhance the mechanical strength and prevent deformation.

(2) Anti-electromagnetic shock
Under electromagnetic transients (such as low-frequency overvoltage and DC bias), the core absorbs part of the energy through material properties, reducing the damage to the winding caused by the impact. For example, the nonlinear saturation characteristics of the silicon steel sheet can limit the sudden change of magnetic flux and avoid excessive vibration of the core.

4. Adapting to the special needs of low-frequency scenarios

The operating frequency range of low-frequency transformers (0~400Hz) requires that the core has targeted design in terms of material, shape and process:

(1) Low-frequency permeability optimization

The magnetic permeability of silicon steel sheets in low frequency bands (such as 50Hz industrial frequency) is better than that of ferrite, which is suitable for high-power transmission. For example, the core of the industrial frequency transformer needs to have sufficient cross-sectional area to carry low-frequency magnetic flux.

(2) Cost and volume balance

In low-frequency scenarios, the power-to-volume ratio of silicon steel sheet cores is better. For example, under the same power, high-performance silicon steel sheet cores can reduce the volume by more than 30%, reducing the amount of copper wire and manufacturing costs.

(3) DC bias resistance

In DC bias (such as geomagnetic induced current) scenarios, the saturation characteristics of the core need to be enhanced through material selection (such as high silicon content steel) and structural design (such as air gap adjustment) to enhance tolerance.

5. Parameters that affect the comprehensive performance of the transformer

The selection and design of the core are directly related to the key indicators of the transformer:

(1) Efficiency and temperature rise

High-performance cores (such as cold-rolled silicon steel) can increase efficiency to more than 95%, while reducing temperature rise by 20%~30%.

(2) Volume and weight

The toroidal core has a high magnetic circuit efficiency and is about 40% smaller in volume and 25% lighter in weight than the E-type core, making it suitable for compact equipment.

(3) Noise control

Low-leakage cores (such as C-type and toroidal) can reduce magnetostrictive noise, making the transformer run quieter