Low frequency transformer – ring transformer

Brief description:

Ring transformer is a type of transformer, whose core is made of cold-rolled silicon steel strip wound into a ring shape, and the coil is uniformly wound around the entire core. This unique closed magnetic circuit structure presents distinct advantages and disadvantages in terms of electrical and physical properties.

In terms of advantages, the leakage pole of the toroidal transformer is small and the efficiency is high. Due to the absence of air gaps, low magnetic resistance, low excitation current, and leakage flux of the circular iron core, which is only about 1/10 of that of ordinary transformers, electromagnetic interference is extremely low. At the same time, its efficiency can usually reach 90% -95%, which is higher than traditional EI type transformers. In addition, the circular transformer has a small volume, light weight, and a high filling coefficient in the circular structure. Under the same power, the volume and weight can be reduced by 30% -50%. It has low operating noise and low temperature rise. The annular iron core can be fastened as a whole without the vibration noise of EI type iron core. Moreover, its high magnetic permeability reduces copper and iron losses, resulting in low heat generation. In addition, the toroidal transformer has strong overload capacity, good coil heat dissipation conditions, and is not easily burned out during short-term overload.

In terms of drawbacks, the anti DC saturation ability of the toroidal transformer is poor. If there is a DC component mixed in the input voltage, it will quickly cause magnetic saturation of the iron core, leading to a sharp increase in current and even damage. Therefore, it is not suitable for direct use in circuits with thyristor phase modulation equipment. At the same time, its production process is complex, requiring a dedicated circular winding machine for winding, and the wire package is difficult to achieve complete uniformity, resulting in slightly poor batch consistency. In addition, the maintenance of toroidal transformers is difficult. Once the coil is damaged, disassembly and rewinding are very troublesome, and the cost is even close to purchasing a new transformer. Finally, its poor high-frequency characteristics are limited by the silicon steel sheet material and are only suitable for 50Hz or 60Hz power frequency applications, making it unsuitable for high-frequency applications.