page_title: Leakage inductance
section_title: Refined inductive leakage factor
hierarchical_section_title: Leakage inductance / Refined inductive leakage factor
caption_attribution_description: English: Transformer main &amp; leakage inductances
context_page_description: Leakage inductance derives from the electrical property of an imperfectly-coupled transformer whereby each winding behaves as a self-inductance in series with the winding's respective ohmic resistance constant. These four winding constants also interact with the transformer's mutual inductance. The winding leakage inductance is due to leakage flux not linking with all turns of each imperfectly-coupled winding.
  Leakage reactance is usually the most important element of a power system transformer due to power factor, voltage drop, reactive power consumption and fault current considerations.
  Leakage inductance depends on the geometry of the core and the windings. Voltage drop across the leakage reactance results in often undesirable supply regulation with varying transformer load. But it can also be useful for harmonic isolation of some loads.
  Leakage inductance applies to any imperfectly-coupled magnetic circuit device including motors.
context_section_description: Referring to the flux diagram in Fig. 6, the following equations hold:
  σP = ΦPσ/ΦM = LPσ/LM ------ (Eq. 3.1  Eq. 2.7)
  In the same way,
  σS = ΦSσ'/ΦM = LSσ'/LM ------ (Eq. 3.2   Eq. 2.7)
  And therefore,
  ΦP = ΦM +  ΦPσ = ΦM + σPΦM = (1 + σP)ΦM ------ (Eq. 3.3)
  ΦS' = ΦM +  ΦSσ' = ΦM +  σSΦM = (1 + σS)ΦM ------ (Eq. 3.4)
  LP = LM +  LPσ = LM + σPLM = (1 + σP)LM ------ (Eq. 3.5  Eq. 1.1b & Eq. 2.14)
  LS' = LM +  LSσ' = LM + σSLM = (1 + σS)LM ------ (Eq. 3.6  Eq. 1.1b & Eq. 2.14),
  where
  σP & σS are, respectively, primary leakage factor & secondary leakage factor
  ΦM &  LM are, respectively, mutual flux & magnetizing inductance
  ΦPσ & LPσ are, respectively, primary leakage flux & primary leakage inductance
  ΦSσ' &  LSσ' are, respectively, secondary leakage flux & secondary leakage inductance both referred to the primary.
  The leakage ratio σ can thus be refined in terms of the interrelationship of above winding-specific inductance and Inductive leakage factor equations as follows:
   ------ (Eq. 3.7a to 3.7e).
caption: Fig. 6 Magnetizing and leakage flux in a magnetic circuit[30][28][31]
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