Inductor Basics By David Adeeb Presenter: David Adeeb • Sr. Technical Marketing Engineer • Based in Florida, USA • Degreed in Electrical / Electronics Engineering • Master’s Degree in Business Administration • Recently join KEMET • Like the outdoors and an avid road cyclist ©KEMET Corporation. All Rights Reserved. 2 Today’s Agenda 1. Definition of an inductor 2. Characteristics of an inductor 3. Inductance 4. Factors that affect inductance 5. Inductor core 6. “Charging” and “Discharging” an inductor 7. Non-ideal inductor ©KEMET Corporation. All Rights Reserved. What is an Inductor? Insulated conductive wire wound (wrapped) around a core that stores energy in the form of a magnetic field when a time-varying current is passed through it. Conductor φ Magnetic flux direction e: electromotive force dφ/dt: change of magnetic flux over the change in time e i di/dt: change in current over the change in time dφ di e = - = - L . [V] dt dt • Inductance unit of measure is “H” (henry) What is an Inductor? (cont’d) Coil Magnetic Magnetic flux φ (Wire) Field Core Material i The coil converts electric energy into e magnetic energy and stores it. Current through the coil of wire creates a magnetic field and stores it. Characteristics of an Inductor • Inductance is an inductor’s ability to store energy as magnetic field (created by the flow of electrical current) • Measured as the ratio of voltage to the change of current with respect to time (in Henries) Permeability - What is that? The permeability of a magnetic core is the characteristic that gives the core the ability to concentrate lines of magnetic flux. Conductor Magnetic core A Magnetic flux direction Magnetic flux direction according to Lenz's law according to Lenz's law lm Permeability of free space Magnetic core Permeability Magnetic Resistance −7 µ = µ0 =4π × 10 µ = µr x µ0 lm Rm = µr x µ0 x A L : Inductance [H] µ : Permeability for Air [H/m] l : Magnetic path length 2 A 0 m N 2 µ : Relative permeability A : Effective area L = = µ . µ . N . r r 0 l N : Number of turns Rm m Rm: Magnetic resistance of core [A/Wb] What Affects Inductance? And How? Turns Core Material more turns = greater amount of magnetic field force. greater magnetic permeability = greater magnetic field flux. Coil Area Coil Length more coil area = less opposition to the formation of longer path for the magnetic field flux = more opposition to the flux magnetic field flux. formation. 2 A L = µr µ0 N lm Why a Core? Functionally Mechanically Magnetically A magnetic core stores A core provides support for its A core provides the medium recoverable energy windings. to concentrate and contain magnetic flux. Core Material Join us on Wednesday to learn more! Air Ferrite Metal (None) (Iron) Composite Different core materials change magnetic field strength. “Charging” an Inductor? Current Time “Discharging” an Inductor? Current Time Non Ideal Inductor: DC Resistance (DCR) Equivalent circuit for a real inductor R L Wire Resistance Ideal Inductor The wire used for the coil of an inductor has resistance that is inherent to the material it’s made from. This is the DCR. 2 DCR Heat Dissipated I R Efficiency (Power Loss) Behavior of Real Inductor L i Rs C Before Self-Resonance Frequency Rp Impedance L C Rs Frequency i After Self-Resonance Frequency Rp Three Types of Losses for an Inductor Copper (Resistive) Loss Core Loss Fringing Loss (more dominant at higher current) (more dominant at lower current) Heat produced by electrical Loss that occurs in a A phenomenon in which the currents in the conductors of magnetic core due to non- magnetic flux flowing in a transformer windings, or other ideal magnetic core. magnetic core spreads out electrical devices. (or fringes out) into the surrounding medium (for example in the vicinity of an air gap) Recap 1. Inductor: insulated conductive wire wound around a core 2. Characteristics: inductance and permeability 3. Inductance: tendency to store magnetic energy 4. Factors: area, length, core, turns 5. Inductor core 6. “Charging” and “Discharging” in a circuit 7. Characteristics of non-ideal inductor ©KEMET Corporation. All Rights Reserved. Comments / Questions? Attendees can submit questions later using this link. Join us for our upcoming webinars: • “Construction and Characteristics of Power Inductors” June 17 @ 9 a.m. EDT / 3 p.m. CEST and 11 a.m. EDT / 8 a.m. PDT • “Explaining Losses In Magnetics-based Components” June 22 @ 9 a.m. EDT / 3 p.m. CEST and 11 a.m. EDT / 8 a.m. PDT .