Bobbin inductors, also known as bobbin filters. Its essence is a common mode inductor, and the magnetic ring common mode inductor is different, bobbin common mode inductor through bobbin support, can be machine automatic winding, the cost is greatly reduced, is conducive to rapid mass production.
At present, there are three common structures, which are EE type, UU type, and ET type.
Type EE is the most common structure of bobbin common mode inductors. bobbin is a double slot, one winding around a slot, and the middle is isolated by a baffle to ensure the insulation of the two windings. The winding periphery is isolated with tape from the magnetic core to avoid bad voltage between the winding and the magnetic core.
The magnetic core is often made of high permeability magnetic material, and the mirror assembly can obtain a large inductance, generally mH class. At present, EE8.3, EE10, EE12, EE13, EE16, EE19, EE25 and so on are commonly used.
UU-type bobbin common mode inductor, named for its shape like "U". The slot is elliptical, which makes maximum use of bobbin winding space. Its core material is similar to the EE type, which is also a high-conductivity material and mirror assembly. However, the UU bobbin common mode inductor requires a steel frame that holds the two "L" cores firmly together.
Under normal circumstances, the product will also be soaked in insulating oil treatment, the viscosity of the insulating oil is conducive to ensuring the reliability of the steel frame and preventing changes in sensitivity. At present, UU9.8, UU10.5, UU16 are commonly used.
ET bobbin common mode inductors for large inductance requirements. The general winding number is very large, mostly for the four-slot structure. Each winding is made of two slots, which is conducive to ensuring the flatness of the winding process, preventing the damage of the wire and the short circuit between turns, and reducing the generation of distributed capacitance. At present, the more common ET24 and ET28 are used a lot in household appliances.
There are many standard products of Bobbin common mode inductors on the market. In addition, due to the sake of mirror assembly, the sensitivity is often defined based on the minimum value (MIN), and the device selection has a large margin, which often does not need to be redesigned, and the manufacturer's standards can be directly selected to meet the needs.