Gapped Core Inductance

The purposeful creation of an air or magnetic gap inside an inductor's core to alter its inductance properties is known as gapped core inductance. The gap modifies the magnetic flux path, which impacts the coil's overall inductance and permits fine-grained control over the inductance value.

Using gapped core inductance is primarily used to adjust the component's inductance value to meet specific needs in electronic circuits. The inductance can be changed without substantially altering the inductor's physical size by creating a gap in the core, providing flexibility in both functioning and design.

Understanding Gapped Core Inductance

Why Do We Want a Gap in the Core Material?

The main purpose of leaving a gap in a magnetic circuit — such as a transformer core — is to mitigate magnetic flux density and prevent core saturation. Introducing a gap increases the reluctance of the magnetic path, thereby diminishing the flux density and maintaining the core below saturation levels.

How Does the Gap Affect the Inductance?

The length of the gap influences both the magnetic flux density and inductance equally. A larger gap diminishes the inductance while concurrently reducing the magnetic flux density — a favorable outcome for averting core saturation.

What Is the Purpose of Leaving a Gap in the Core?

Introducing a gap in the core serves a dual purpose:

• Diminishes the magnetic flux density to prevent core saturation
• Augments the reluctance of the magnetic circuit, thereby reducing the flux flowing through the core

How Does the Gapped Core Inductance Calculator Work?

The calculator considers various physical parameters of the inductor — including core material, gap length, and winding configuration — to compute the gapped core inductance. This tool proves vital for designers, enabling them to optimize the performance of inductors.

What Is an Air-Gapped Magnetic Core?

An air-gapped magnetic core is a specific type of inductor core featuring a deliberate gap, often filled with a non-magnetic substance like air or nylon, to avert saturation. This design affords superior control over magnetic flux density and prevents core saturation effectively.

Applications

• Power Supply Filtering
• Switching Regulators and Converters
• Audio Equipment
• RF Circuits
• Motor Drives and Control Systems

About This Calculator

This online calculator helps you determine the air core inductance for a variety of applications. Traditionally, gapped cores were used to control the inductance and raise the air core inductors' quality factor (Q).

Formulas

$A_l = \frac{4\pi \times A_e}{\left(\frac{l_e}{\mu_r}\right) + l_g}$

$L = A_l \times N^2 \times 10^{-3}$

$\frac{B}{I} = \frac{0.4\pi \times N}{\left(\frac{l_e}{\mu_r}\right) + l_g}$

where:

• $A_l$ = Inductance per turn² (nH/turn²)
• $N$ = Number of Turns
• $A_e$ = Gap Area (cm²)
• $l_e$ = Core Length (cm)
• $\mu_r$ = Relative Permeability
• $l_g$ = Gap Length (cm)
• $\frac{B}{I}$ = Flux Density per Amp (Gauss/A)