Basic issues in the design of power transformers

[jacksu2023]

The basic issues in the design of power transformers are magnetic flux and current density. The current of a transformer is directly proportional to its capacity, and the current density (i.e. the thickness of the wire) is considered based on the heating capacity of the conductor. For magnetic flux, the basic relationship of electromagnetism is u=4.44fw, where u is voltage, f is frequency, here is 50Hz, fixed value; W is the number of turns of the coil; φ The middle is the magnetic flux. Due to material limitations, the magnetic flux density B of silicon steel sheets can generally only be designed to 1.4-1.8 Tesla. Therefore, it is necessary to increase φ， Generally, only the cross-sectional area of the iron core can be increased. The iron core of a transformer is generally a three-phase column type, and the cross-sectional area of the iron core can be determined according to the above formula. The size of the iron core window should consider the principle of placing the coil inside. The larger the capacity of the transformer, the thicker the wire, and the larger the window of the iron core.

In the design of power transformers, the consumption of copper and iron can be balanced. Because once the capacity of the transformer is determined, the current is determined, and the thickness of the wire is also determined, increasing the number of turns W and magnetic flux φ It can be smaller, and the cross-sectional area of the iron core can be smaller, but to wrap these turns in, the window of the iron core should be larger; On the contrary, reducing the number of turns W results in magnetic flux φ It needs to be larger, with a larger cross-sectional area of the iron core, but the window of the iron core can be smaller.

In the design process of power transformers, it is necessary to consider the magnitude of magnetic flux and current density, control them within a reasonable range, and ensure that they have a good operating state to avoid the occurrence of some faults.