Toroidal Inductors
Toroidal inductors are passive electronic components that have magnetic cores in the form of a donut or ring, which are known as toroidal shapes. Their purpose is to assist with energy efficiency when low frequencies require inductance, which measures the amount of current flowing through a conductor. Inductance opposes any change in the flow of electrical current. The magnetic field of a toroidal inductor is as strong as the value of the current passing through it.
The shape of toroidal inductors is what makes them different from all other forms of inductors, such as ferrite and air core inductors. The round donut shape of the core creates a closed loop that allows for a wide frequency range and helps minimize electromagnetic (EMI) and radio frequency (RFI) interference. In addition, magnetic flux is concentrated in the core.
Toroidal inductors slow down current surges and spikes by storing the energy that is produced in the magnetic field of their core. At the appropriate time, the stored energy is released. They are used in electrical power and electronic devices to choke, block, attenuate, and filter high-frequency noise and for storing and releasing energy. When toroidal inductors are placed in a series with a conductor, they block and impede changes in current and perform as low pass filters.
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How Toroidal Inductors Work
There are many shapes of inductors with C core, E core, and U core being three of the most common. They have many purposes and uses, which is the reason for so many configurations and types with the differences between the types being in regard to the type of power application. The windings of inductors is the most important consideration when selecting an inductor, since it affects the properties of an inductor.
Properties
The closed loop of the core of a toroidal inductor generates high inductance and has a strong magnetic field with low electromagnetic interference. The outstanding characteristic of toroidal inductors is their higher Q factor and high inductance, which is because of the fewer number of turns of the core. Toroidal inductors do not have an air gap, a factor that makes their operation quieter than other forms of inductors.
Theory
When current passes through a toroidal inductor, a magnetic field is produced, the strength of which depends on the amount of current that is passing through. The flux of the magnetic field is the number of circles that are perpendicular to the direction of the current. The lines of the flux make complete loops. As the current changes, the flux produced changes and links to the coil. Changes to the current and flux happen at the same rate and induce electromagnetic force that is in opposition to the voltage across the coil.
With a toroidal coil, alternating current (AC) voltage is applied to the coil at both of its ends, which generates a change in magnetic flux. A self-induced electromotive force (EMF) in the coil is opposite to the direction of the AC voltage. Magnetic energy conversion takes place, which happens in the windings of a toroidal inductor. Toroidal inductors use low impedance to suppress high frequency current in electrical circuits.
Compared to a Solenoid
Solenoids have long conducting wires that are wound in a helical shape like a spring with turns in a circular loop. Gaps in the turns are filled with solid coils or the solenoid’s plunger. When the coils are connected to a current source and current passes through the coil, a magnetic field is generated the force of which is applied to the plunger, which moves inside the coil. A solenoid converts electrical energy into mechanical energy.
The working principle of toroidal inductors and solenoids is electromagnetism where a magnetic field is generated. The strength of the generated magnetic field is the same, making solenoids and toroidal inductors forms of electromagnets.
Aside from their different shapes, where a solenoid is cylindrical and a toroidal inductor is a donut shape, the magnetic field of a solenoid is generated outside the solenoid, while the magnetic field of a toroidal inductor is in its core. A solenoid has an even and uniform magnetic field, whereas toroidal inductors have a non-uniform magnetic field. The main function of a toroidal inductor is to control electrical current while a solenoid is a mechanical electronic tool that is used to turn devices on and off.
The Operation of a Toroidal Inductor
The principle of a toroidal inductor is in regard to the relationship between current and magnetic fields. All wires produce a magnetic field when current passes through them. As the strength of the current increases, the strength of the magnetic field increases. With straight wires, the increase and decrease of the magnetic field varies with the electrical current. By winding the wires around a toroid, the strength of the magnetic field increases.
Inductance
Inductance affects the flow of electrical current in a circuit. It is when a change in current causes a change in voltage. The donut shape of a toroidal inductor allows for higher inductance. The operation of the coil in a toroidal inductor is to oppose any change in the current that flows through it. As the magnetic field grows in the toroidal coil, it induces an EMF that opposes current flow, which is a temporary effect that changes when there is a steady flow of current.
The Core
The core of a toroidal inductor is its central component and is made up of a form of magnetic metal and coiled wires. The windings of the wires generate the magnetic field when electrical current passes through a toroidal inductor. The efficiency and high inductance of a toroidal inductor is because of the donut shape of the core that creates its closed loop that generates a stronger magnetic field. Since the core is a solid closed circle without air gaps, leakages are prevented.
The selection of the materials that are used to produce the core are very carefully chosen, due to the core being a vital part of a toroidal inductor. Steel, due to its strength and endurance, is commonly used for cores. A popular type of core material is non-metallic ferrite that is a high resistive material with high magnetic permeability in the presence of high frequencies.
Temperature Coefficient
All forms of equipment react to changes in temperature, which is especially critical for toroidal inductors. The temperature coefficient of toroidal inductors changes the performance of the coil in relation to fluctuations in temperature. In a toroidal inductor, an increase in temperature increases the resistance of the core but causes a decrease in inductance.
Conclusion
Toroidal inductors are passive electrical components that store energy in a magnetic field. They are one of the most popular forms of inductors for computers, sound systems, and servers due to their having a very low noise level. The toroidal or round shape of toroidal inductors differentiates them from other forms of inductors that are in the shapes of the letters C, E, and U.