Two-Cored Inductor Reduces Near Magnetic Field Couplings

Technology #16706

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Shuo Wang
Boyi Zhang
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Richard Croley
Assistant Director 352-392-8929
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US Patent Pending

CM Inductor Design Lessens Near Magnetic Field Radiation while Improving DM Inductance and Reducing DM noise

This common mode (CM) inductor design both reduces the near magnetic field couplings between components in electronic systems and attenuates differential-mode (DM) noise. Due to the demand for high power density in electronic systems, their components tend to sit close together increasing the chances of undesired near magnetic field couplings. These couplings can reduce the performance of a circuit or stop it from functioning altogether. To prevent this, smaller and denser electronic systems must be manufactured with internal shielding.

Researchers at the University of Florida have developed a two-cored inductor design with a lower near magnetic field radiation than conventional inductors, eliminating the need for shielding. This proposed inductor also has the added benefit of reducing more DM noise than conventional CM inductors with same size. When operating in high frequency range, the inductance of conventional CM inductors will decrease while the proposed CM inductor could maintain its high inductance and attenuate CM noise up to a higher frequency. It can be used in single-phase, three-phase, or multi-phase power electronics systems, as well as electromagnetic interference (EMI) filters and energy storage devices.


CM Inductor reduces risk of magnetic couplings and improves DM inductance in power electronic systems


  • Generates less near magnetic field radiation, increasing CM performance
  • Has higher DM inductance, reducing DM noise production
  • Reduces the size of DM inductor, achieving higher power density
  • Has inductance in high frequency range, enhancing the filters' higher frequency performance


This CM inductor design has two inductor cores, the smaller core positioned within the larger. Each core has two winding structures wrapped around each. These windings are symmetrical and in opposite directions to each other, allowing the coupling between them to outperform conventional inductor winding structures. The two cores, and small air gaps between them, provide reluctance paths for the DM magnetic flux. This means that the two-cored inductor has both small near magnetic field radiation and better DM inductance.