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.^[1][2]

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 (attenuating higher frequencies) of some loads.^[3]

Leakage inductance applies to any imperfectly coupled magnetic circuit device including motors.^[4]

Leakage inductance and inductive coupling factor

The magnetic circuit's flux that does not interlink both windings is the leakage flux corresponding to primary leakage inductance L_P^σ and secondary leakage inductance L_S^σ. Referring to Fig. 1, these leakage inductances are defined in terms of transformer winding open-circuit inductances and associated coupling coefficient or coupling factor ${\displaystyle k}$.^[5][6][7]

The primary open-circuit self-inductance is given by

${\displaystyle L_{oc}^{pri}=L_{P}=L_{M}+L_{P}^{\sigma }}$ ------ (Eq. 1.1a)

where

${\displaystyle L_{P}^{\sigma }=L_{P}\cdot {(1-k)}}$ ------ (Eq. 1.1b)

${\displaystyle L_{M}=L_{P}\cdot {k}}$ ------ (Eq. 1.1c)

and

• ${\displaystyle L_{oc}^{pri}=L_{P}}$ is primary self-inductance
• ${\displaystyle L_{P}^{\sigma }}$ is primary leakage inductance
• ${\displaystyle L_{M}}$ is magnetizing inductance
• ${\displaystyle k}$ is inductive coupling coefficient

It therefore follows that the open-circuit self-inductance and inductive coupling factor ${\displaystyle k}$ are given by

${\displaystyle L_{oc}^{sec}=L_{S}=L_{M2}+L_{S}^{\sigma }}$ ------ (Eq. 1.2), and,

${\displaystyle k={\frac {\left|M\right|}{\sqrt {L_{P}L_{S}}}}}$, with 0 < ${\displaystyle k}$ < 1 ------ (Eq. 1.3)

where

${\displaystyle L_{S}^{\sigma }=L_{S}\cdot {(1-k)}}$

${\displaystyle L_{M2}=L_{S}\cdot {k}}$

and

Zdroj:https://en.wikipedia.org?pojem=Leakage_inductance
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