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In a magnetic circuit, when magnetic flux is passing across the air gap, then effective area of the gap increases and magnetic flux density decreases in the gap. This effect is known as ______.
magnetic hysteresis
magnetic fringing
magnetic leakage
magnetising force
magnetic fringing
Magnetic fringing is the phenomenon where magnetic flux lines bulge outward at the edges of an air gap in a magnetic circuit. This causes the effective cross-sectional area of the air gap to appear larger than the physical area of the core, consequently reducing the flux density in the gap.
Magnetic fringing is the phenomenon where magnetic flux lines bulge outward at the edges of an air gap in a magnetic circuit. This causes the effective cross-sectional area of the air gap to appear larger than the physical area of the core, consequently reducing the flux density in the gap.
B=A╬жтАЛ тАФ Relation between flux density, flux, and area
AeffтАЛ=(a+lgтАЛ)(b+lgтАЛ) тАФ Effective area approximation for a rectangular pole of cross-section a├Чb and air gap lgтАЛ
As flux lines travel through the high-reluctance air gap, they experience a repulsive force between neighboring lines due to the absence of the high-permeability iron core. This force causes the flux to spread laterally beyond the boundaries of the iron poles. Because the total flux remains constant, the increase in the effective area AeffтАЛ results in a decrease in the flux density B=AeffтАЛ╬жтАЛ.
Fringing increases the effective area of the air gap.
Fringing leads to a reduction in local flux density.
The effect becomes more pronounced as the air gap length increases.
Fringing increases the total reluctance of the magnetic circuit compared to calculations assuming ideal flow.
Increased calculation complexity in design
Reduces the effective magnetic flux density available for electromagnetic torque
Design of electric motors
Transformer core assembly
Magnetic actuators and relays
Magnetic leakage (Option C) refers to flux that bypasses the intended air gap entirely through the surrounding air, whereas fringing occurs specifically at the edges of the intended gap.
Magnetic hysteresis (Option A) is the energy loss due to domain wall movement in ferromagnetic materials.
Magnetising force (Option D) is the magnetic field intensity H produced by current-carrying windings.
B is correct тАФ Magnetic fringing refers to the outward bowing of magnetic flux lines at the edges of an air gap, increasing the effective area and reducing flux density.
Always remember that fringing affects the area (increasing it), while leakage affects the total flux (decreasing the flux reaching the gap).
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