Proximity Effect

Definition

Proximity effect refers to the phenomenon where the effective current flowing cross-sectional area inside a conductor is reduced due to the close proximity of nearby current-carrying wires.

Impact

• Higher AC Resistance: The proximity effect leads to an increase in the AC resistance of the conductor. This increase in resistance is more pronounced at higher frequencies. The interaction between the magnetic fields generated by neighboring wires causes a non-uniform distribution of current, resulting in a concentration of current near the surface of the conductor. As a result, the effective cross-sectional area available for current flow decreases, leading to higher resistance.

• Higher Power Loss: The increased resistance caused by the proximity effect results in higher power loss in the conductor. This power loss, known as proximity effect loss, is a consequence of the increased current density near the surface of the conductor. The higher the frequency of the AC current, the greater the power loss due to the proximity effect.

• Lower Quality Factor of Inductor: The proximity effect can have a significant impact on the performance of inductors. The quality factor (Q-factor) of an inductor, which represents its ability to store and release energy efficiently, is negatively affected by the proximity effect. The increase in resistance and power loss reduces the efficiency of energy transfer in the inductor, leading to a lower Q-factor. This can have implications for applications such as power electronics and RF circuits, where high-quality inductors are essential for optimal performance.

Summary

Understanding and mitigating the proximity effect is important in the design and operation of electrical systems, especially those involving high-frequency AC currents. Proper conductor spacing, geometric arrangement, and use of techniques such as litz wire (stranded wire with individually insulated strands) can help minimize the impact of the proximity effect and reduce its detrimental effects on resistance, power loss, and inductor performance.