Basic issues in power transformer design

Power transformer is used to convert AC voltage, current and transmit AC power is a static electrical equipment, in the design process need to consider a variety of factors, maintain a good structural arrangement, extend the use time of the equipment.
The fundamental problems of power transformer design are magnetic flux and current density. The current of the transformer is proportional to the capacity, and the magnitude of the current density (i.e. the thickness of the wire) is considered according to the heat generated by the conductor. For magnetic flux, the basic relationship of electromagnetism is u=4.44fw, where u is the voltage and f is the frequency, here it is 50Hz, fixed value; w is the number of turns of the coil; In the φ is the magnetic flux. Since the magnetic flux density B of silicon steel sheet is limited by the material, it can generally only be designed to 1.4-1.8 Tesla, so to increase the φ, generally only the cross-sectional area of the iron core can be increased. The core of the transformer is generally a three-phase column type, the cross-sectional area of the iron core can be determined according to the above formula, and the size of the core window should consider the principle of putting the coil in. The larger the capacity of the transformer, the thicker the wire, and the larger the window of the core.
In the design of power transformers, the amount of copper and iron can be balanced. Because once the capacity of the transformer is determined, the current is determined, the thickness of the wire is determined, increase the number of turns W, the magnetic flux φ can be smaller, the cross-sectional area of the core can be smaller, but to wind these turns in, the window of the iron core should be larger; On the contrary, by reducing the number of turns W, the magnetic flux φ will be larger, and the cross-sectional area of the iron core will be larger, but the window of the iron core can be smaller.