The frequency of the Ac current transformer refers to the number of periodic changes in its unit time, in Hertz, which is inversely related to the period. The frequency of alternating current in daily life is generally 50 Hz or 60 Hz, and the frequency of alternating current involved in radio technology is generally large, reaching a measure of kilohertz (KHz) or even millions of hertz (MHz). Different power systems have different AC frequencies, usually 50 Hz or 60 Hz.
Ac current transformer are widely used for power transmission because AC transmission is more efficient than DC transmission under previous technical conditions. The power dissipated by the transmitted current on the conductor can be obtained by Joule's law (P = I 2R). Obviously, to reduce the energy loss, it is necessary to reduce the current transmitted or the resistance of the wire. Due to cost and technology limitations, it is difficult to reduce the resistance of currently used transmission lines (such as copper wires), so reducing the transmitted current is an effective method. According to P = IU (actually active power
Increasing the voltage of the grid can reduce the current in the conductor to save energy. The easy-to-accelerate characteristics of AC power are just right for high-voltage transmission. Using a simple step-up transformer, the AC can be raised to thousands to hundreds of thousands of volts, resulting in minimal power loss on the wires. In the city, a step-down transformer is generally used to reduce the voltage to tens of thousands to several thousand volts to ensure safety, and then reduce to the mains voltage or the applicable voltage supply appliance before entering the household.