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--- foreign_object_detection_in_the_qi_standard [2025/05/01 13:35] – tm
+++ foreign_object_detection_in_the_qi_standard [2025/05/01 14:17] (current) – [1.Q-factor detection] tm
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 When a metal object (MO) enters the coil’s magnetic field, it disturbs the field and induces eddy currents in the object. These eddy currents cause the coil’s inductance 𝐿 to decrease and its resistance 𝑅 to increase due to additional energy losses. As a result, the Q-factor drops, which can be used as an indication of a foreign object in wireless power transfer systems. As examined by Tian et al., when metal objects enter the charging zone, the quality factor of the Rx coil exhibits a significant downward trend, making it a suitable index for MOD within WPT systems such as the Qi standard (Tian et al., 2022, p. 3; Wireless Power Consortium (WPC), n.d.).
 Practically, the quality factor of the receiver coil will be measured in a [[Power transfer architecture of the Qi standard|pre-power transfer phase]]. Next, Figure 2 shows how Q-factor FOD is created (Infineon, 2023, p. 5; Technologies, 2023, p. 25).