The reluctance is the property of the magnetic material, which provides opposition to the flow of magnetic flux through a given volume of space or material. The reluctance of magnetic circuits is analogous to the resistance of electric circuits.
The lower the reluctance, the easier it is for the magnetic flux to flow through the magnetic material. The opposite of reluctance is permeability, which is analogous to the conductivity in the electric circuit. Magnetic materials have low reluctance and high permeability, and nonmagnetic materials have high reluctance and low permeability.
Comparison of Magnetic and Electric Circuit
The above diagram shows an analogy of electric and magnetic circuits. The magneto-motive force(MMF) is equivalent to emf in the electric circuit. Flux is analogous to the electric current, and the reluctance is analogous to the resistance in an electric circuit.
When voltage is applied to a coil with N turns, current starts flowing through the coil. Let the magnitude of the current be I amps.
The Magneto-motive force MMF produced is equal to the product of the current and the number of turns.
The current flowing in the coil produces the magnetic flux (Φ), which travels through the magnetic core. The magnitude of the flux depends on the MMF and the reluctance of the magnetic circuit. If the reluctance offered by the magnetic material is more, the magnitude of the magnetic flux will be less. The flux can be increased by lowering the reluctance of the magnetic material.
If the uniform section having different values of length, cross-section area, and permeability are added, the non-uniform magnetic circuit can be made.
By adding the reluctance of the uniform section of the magnetic circuit, the reluctance of the non-uniform circuit can be calculated.
Formula of Magnetic Reluctance
The reluctance( Rm) of the magnetic circuit can be expressed as ;
SI unit of reluctance is AT / Wb (ampere-turns / Weber). The reluctance(Rm) of the magnetic circuit is directly proportional to the length of the conductor and inversely proportional to the cross-section area of the conductor.
The permeance is one of the parameters that measure the property of the magnetic circuit to allow the magnetic flux to pass through it. The permeance is inversely proportional to the reluctance. It is expressed by the following expression.
