All rights reserved by Wrth Elektronik, also in the event of industrial property rights. All rights of disposal such as copying and redistribution rights with us. www.we-online.com Behind the Spec of Power Inductors Wuerth Elektronik eiSos Alexander Gerfer, CTO March 16 - 20, 2014 APEC Industrie Session Behind the Spec of Power Inductors 2 Agenda Inductor Selection Power Inductor Specsheet Definitions The Fastest Way : Component Selector 3 Inductor Selection shape DCR, ) WE-PD 1260 : 744 771 156 Irated=2,01A Isat=2,35A at 3 , 0=rchoose additional: 744 771 147 (47H) + 744 771 168 (68H) 12 POWER INDUCTOR SPECSHEET DEFINITIONS 13 Saturation Current ? 14 = Print in the data sheet and in the catalogue, drop of the inductance value Saturation Current 15 Saturation Current 010203040506070809010011005101520253035inductance L/Lo %L= - 10% Saturation Current I A Definition Wurth Elektronik: e.g. WE-PD the saturation current always refers to a certain inductance drop and differs in Inductor construction and varies by manufacturers ! check the specification ! L= - 30% Isat = 25 A Isat = 30 A 16 Saturation current 17 Saturation Current vs Core Material 0,001,002,003,004,005,006,007,008,009,0010,0011,0002468101214Current (A)L (H)WE-SI WE-PD WE-SD WE-HCI Material: NiZn AirGap: big Material: WE-Perm AirGap: small Material: Iron AirGap: distributed Material: NiZn AirGap: small 18 Rated Current ? 19 Rated Current ? = Rated Current describes the self generated heating of Power Inductor by DC-current flow (only) and is free to manufacturesr specification definitions ! 20 Similar measurements but different ratings Rated Current: Measuring Standards ? For measuring the rated current (e.g. 40K temperature rise) a DC current must be driven through the inductor. Contacting the inductor means to take heat energy away from the inductor (heatsinking) The most objective method does not cool down the inductor during measurement ! 21 Rated current Derating ! the max operating temperature of the inductor is 125C (Can be higher 155C, like WE-HCI or WE-PDF series,) Example: at 100C ambient temperature only 60% of the rated current can be permitted derating of 40 % 22 shielded unshielded smaller l leff bigger l leff influence of an air gap Shielded vs Unshielded Inductors 23 e.g. WE-PD Series reduction of magnetic stray field increased Rated Current reduced DCR for same L-value compared to unshielded construction Disadvantage: reduction of Saturation Current compared to same L-value unshielded Shielded Power Inductors Advantage: 24 stray field - shielded vs. unshielded 25 unshielded shielded stray field - unshielded vs. shielded 26 COMPONENT SELECTOR www.we-online.com/component-selector 27 27 Component Selector www.we-online.com/component-selector 28 28 29 29 30 Component Selector 30 31