IEVref: 221-03-43 ID: Language: en Status: Standard Term: (magnetic) total harmonic distortion factor Synonym1: Synonym2: Synonym3: Symbol: THDF Definition: mathematical expression used for the evaluation of characteristics of magnetic materials and expressed in decibels by: $TH{D}_{\text{F}}=20\text{\hspace{0.17em}}\mathrm{lg}\left(\frac{{V}_{\text{m}}/{V}_{\text{f}}}{{\mu }_{\text{ea}}/CCF}\right)$ where ${V}_{\text{m}}=\sqrt{\sum _{n=1}^{\infty }{V}_{n}^{2}}$, where Vn is the amplitude of the n-th harmonic component of the waveform, Vf is the amplitude of its fundamental component, μea is the amplitude permeability, CCF is the Circuit Correction Factor NOTE 1 – In practice, $CCF=1/\sqrt{1+{\left(3\omega {L}_{1}/{R}_{\text{s}}\right)}^{2}}$ stands for the Circuit Correction Factor and is given in the approximation for the third harmonic, which is valid for measurements without applied DC bias. L1 is the primary inductance. Rs is the total source resistance (50 Ω). NOTE 2 – THDF is sometimes expressed in decibels. Publication date: 2007-04 Source: Replaces: Internal notes: 2015-06-22: Adjective d.c. replaced by DC. JGO 2012-01-15: German term corrected in accordance with mail received from Anne Seeger DKE 2015-01-14. JGO 2017-02-27: "dB" deleted from the equation and "designated by" corrected to "expressed in". See mail exchange with RS and JS 2016-01. JGO 2017-06-02: Cleanup - Remove Attached Image 221-03-42a.gif 2017-06-02: Cleanup - Remove Attached Image 221-03-42b.gif 2017-06-02: Cleanup - Remove Attached Image 221-03-42c.gif CO remarks: TC/SC remarks: VT remarks: Domain1: Domain2: Domain3: Domain4: Domain5: