![]() ![]() Let’s assume that we have an air gap, and the permeability of air (free space) is a constant Solving the above equation for magnetomotive force, we get Substituting the value of H from Equation 2 into Equation 1, we get Where, Fm is Magnetomotive force (mmf), in ampere-turns, l is length of material (gap), in meters Now, magnetizing force of the air gap is determined as below, H is magnetic field strength, in ampere-turns/meter Where, μ is permeability of a material, in henrys/meter Where, B is magnetic flux density in Teslas (T)Īs we know that permeability of any material can be stated as the ratio of the magnetic flux density to the magnetic field intensity of a material. Let’s look at the basic formula to calculate flux density. How to Calculate Flux Density in an Air Gap? However, with a larger air gap we might have to take that change in area into consideration when we start doing flux density calculations. With small air gaps, fringing can be neglected unless otherwise noted. As we increase the air gap, it increases flux fringing and vice versa. This flux fringes out into the neighbouring air path and such paths for flux are called flux fringing resulting in a non-uniform flux density in the air gap. Also, the air gaps help the magnetic flux to expand outside the magnetic circuit. The amount of air or another non-magnetic material like a fibre plate or fibre board increases the reluctance of the circuit, thereby increasing the amount of current that we could put in a coil before we reach saturation. One of main reasons for an Air Gap is to increase the reluctance of the magnetic circuit. In this circuit, there is only one path for the magnetic circuit and thus it can be called as a series magnetic circuit.įig 1. Let’s discuss different reasons why air gaps are crucial in practical applications. Why Do We Need Air Gap in a Magnetic Circuit?Ĭonsider a magnetic circuit with an air gap as below. Well, what exactly is the function of the air gap? Depending on application, air gap may be filled with a non-magnetic material such as gas, water, vacuum, plastic, wood etc. This allows a substantial part of the magnetic flux flows through the gap. An air gap is a non-magnetic part of a magnetic circuits and it is usually connected magnetically in series with the rest of the circuit. A magnetic circuit is where a magnetic flux is circulated or follow through a closed area or path. In this blog we will review the theory of the Air gaps in magnetic circuits. ![]()
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