Magnetic Core

A magnetic core consisting of a plastic or ceramic toroid around which is wound a strip of thin magnetic tape possessing a square hysteresis-loop characteristic.

A magnetic core is a piece of magnetic material with a high permeability used to confine and guide magnetic fields in electrical, electromechanical and magnetic devices such as electromagnets, transformers, electric motors, inductors and magnetic assemblies. It is made of ferromagnetic metal such as iron, or ferrimagnetic compounds such as ferrites. The high permeability, relative to the surrounding air, causes the magnetic field lines to be concentrated in the core material. The magnetic field is often created by a coil of wire around the core that carries a current. The presence of the core can increase the magnetic field of a coil by a factor of several thousand over what it would be without the core. The use of a magnetic core can enormously concentrate the strength and increase the effect of magnetic fields produced by electric currents and permanent magnets. The properties of a device will depend crucially on the following factors: ⁕the geometry of the magnetic core. ⁕the amount of air gap in the magnetic circuit. ⁕the properties of the core material. ⁕the operating temperature of the core. ⁕whether the core is laminated to reduce eddy currents.

Magnetic Core electromagnet

Magnetic Core electromagnet

Magnetic components have been used in several power electronic devices for decades. They are used in a wide range of applications. In order to implement the designed magnetic components, it is essential to have a good understanding of magnetic materials and associated technology.

In the previous article, we learned about the basic aspects of magnetic materials including their classification, core materials, and shapes. Read on to learn more about various core sizes, core assembly, choice of components, and applications of magnetic materials.

The core is a specific design of magnetic material in a particular shape that possesses high magnetic permeability. It is employed to confine and guide the magnetic fields in electrical, electromechanical, and magnetic devices.

The core is typically made of a ferromagnetic material like iron or of ferrimagnetic compounds such as ferrites. The idea behind using high permeability material for this purpose is to be able to have the magnetic field lines concentrated in the core material.

The size of the core varies for different applications based on the core material’s power or energy level. There are several standard sizes available off-the-shelf to cater to the needs, and also scope for customizing the sizes for specialized applications.

The size of the coil former depends on the size and needs to be chosen accordingly. The datasheets provided by the manufacturer come in handy for reviewing the standard sizes of the magnetic core and other related components.

Magnetic cores are highly permeable ferrous metal pieces which are usually wrapped with a wire coil and used in the production of mechanical or magnetic devices. Due to the high permeability of the metal core, it is capable of concentrating magnetic field lines within itself, creating a much stronger magnetic field. These component parts are used in a variety of industrial applications, including electrical transformers, electromagnets, motors, and induction devices.

Choice of Components

The selection of ferrite core shapes depends on many factors. Each shape has some key advantages over the other based on the application at hand. In most of the scenarios, there is no perfect choice and the decision is a compromise accounting for the must-haves. Along with the cores, it is equally crucial to order relevant accessories for the same like coil formers and the mounting hardware.

Another aspect to keep in mind during the design and implementation of the core is the aspect of the air gap. Cores with an air gap are useful for inductors and their applications. The variants in this type are based on the difference in air gap lengths. On the other hand, core without air gap is employed in transformer-based applications.

When assembled properly, can create very strong, concentrated magnetic currents. There are five basic factors that determine the effectiveness of a magnetic core. When all five conditions are met, extremely powerful magnetic cores can enhance the magnetic fields created by electricity and permanent magnets.

The five primary factors in magnetic core design are geometric shape, air gap, the core metals properties, operating temperature, and lamination. The shape and air gap of the magnetic core effect the path of the magnetic field. The properties of the metal and the operating temperature have an effect on how the magnetic field is concentrated and how the core itself reacts to magnetic forces. Lamination of the core further effects magnetic paths and concentration by eliminating eddy currents, which could disrupt typical magnetic fields or cause excess heat build-up.

While a core could, by definition, be any piece of ferrous metal wrapped in wire, there are a few basic shapes which are predominately used in industrial applications. These shapes include the straight cylindrical core, the I core, the C or U core, the E core, the pot core, the toroidal core, the ring core, and the planar core. Each of these shapes provides specific magnetic field concentration properties. These magnetic core shapes can be used to good advantage, sometimes increasing the magnetic field of a coil by more than 1,000 times the coils initial magnetic field.

In some cases, the magnetic core is subject to energy loss during operation, due to the properties of the metal it is made from. In cases where a magnetic current must be switchable, the formation of a permanent magnetic field by the core could prove detrimental. For example, an electrical transformer core that becomes permanently magnetized may be rendered unusable for its task. This unwelcome magnetism is called hysteresis and can be circumvented by the use of magnetic core metals with a lower hysteresis point. Such metals are known as soft metals and include soft iron and laminated silicon steel.

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