page_title: Gyrator–capacitor model
section_title: Magnetic capacitance
hierarchical_section_title: Gyrator–capacitor model / Magnetic capacitance
caption_attribution_description: English: Giving the formula for the permeance of a rectangular prism.
context_page_description: The gyrator–capacitor model - sometimes also the capacitor-permeance model - is a lumped-element model for magnetic circuits, that can be used in place of the more common resistance–reluctance model. The model makes permeance elements analogous to electrical capacitance rather than electrical resistance. Windings are represented as gyrators, interfacing between the electrical circuit and the magnetic model.
  The primary advantage of the gyrator–capacitor model compared to the magnetic reluctance model is that the model preserves the correct values of energy flow, storage and dissipation. The gyrator–capacitor model is an example of a group of analogies that preserve energy flow across energy domains by making power conjugate pairs of variables in the various domains analogous. It fills the same role as the impedance analogy for the mechanical domain.
context_section_description: Magnetic capacitance is an alternate name for permeance, (SI unit: H).  It is represented by a capacitance in the model magnetic circuit.  Some authors use  to denote magnetic capacitance while others use  and refer to the capacitance as a permeance. Permeance of an element is an extensive property defined as the magnetic flux, , through the cross sectional surface of the element divided by the magnetomotive force, , across the element'
  
  For a bar of uniform cross-section, magnetic capacitance is given by,
  where:
   is the magnetic permeability,  
   is the element cross-section, and  is the element length.
  For phasor analysis, the magnetic permeability and the permeance are complex values.
  Permeance is the reciprocal of reluctance.
caption: Permeance of a rectangular prism element
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