Low-frequency transformers are mainly used to transmit low-frequency signals and energy conversion, and can be divided into many types according to their structure and working principle. Core-type transformers use ferrite cores or iron cores as magnetic circuits, and realize voltage conversion through coil winding.

They have the advantages of small size, light weight, high efficiency, and low temperature rise, and are widely used in various electronic devices; the shell-type transformer magnetic circuit is located outside the coil, and usually uses an iron shell or aluminum shell as the magnetic circuit. It has strong anti-interference ability and high stability, and is suitable for high-frequency and high-power occasions; the wound transformer directly winds the coil on the iron core, which has a simple structure and low cost, but the efficiency is relatively low due to the long magnetic circuit; the mutual inductor, as a special low-frequency transformer, is mainly used to measure and protect the current and voltage in the power system. It has the characteristics of high precision, high stability, and strong anti-interference ability, and plays an important role in the field of power system measurement, protection and control.

Low-frequency transformers are widely used in electronic equipment and power systems. They are used for coupling between amplifier circuits in audio equipment, and for signal coupling transmission and impedance matching in input and output transformers; they are used for signal transmission and coupling in communication systems, such as isolating lines and providing impedance matching in telephone exchanges, and signal coupling transmission in radio communications; in power systems, mutual inductors ensure the safe and stable operation of power systems.