Why Are Power Transformers Needed?

A power plant intends to transmit electrical power P=sqrt(3)*UIcosφ to the area where electricity is consumed. When P and cosφ are constant, a higher voltage results in a smaller current in the transmission line, thus reducing losses and saving conductive materials. Therefore, using high voltage for long-distance power transmission is the most economical. The highest AC transmission voltage in my country has reached 500kV. Such a high voltage cannot be directly produced by generators, considering both the safe operation of generators and manufacturing costs. Generator output voltages are generally 3.15kV, 6.3kV, 10.5kV, and 15.75kV, therefore, step-up transformers are necessary to increase the voltage for long-distance transmission.

Why are distribution transformers needed? After electrical energy is transmitted to the area where electricity is consumed, to meet the voltage requirements of electrical equipment, transformers at various levels are needed to reduce the voltage to the required value for various electrical appliances.

In terms of electricity, most electrical appliances require voltages of 380V, 220V or 36V, and a few motors also use 3kV, 6kV or other voltages.