7 Practical Applications Products of Inductors

  Inductors are well known for their wide range of application in electronic circuit designs. In this article, we are going to introduce 7 popular applications of inductors. After reading the article, you will have the background knowledge of these applications, including transformers, energy storage, ferrite beads, inductive sensors, induction motors, filters, and electromagnetic relays. So, let’s start with transformers.

1. Transformers

  Transformers are common inductor applications which are seen in power supplies and power systems. Basically, a transformer is made of multiple inductors that share the same magnetic field and is used to change the voltage levels of a system. For instance, a transformer can change a 120V or 240V AC to another voltage level that a laptop, a smartphone, or any loT devices requires. A very basic transformer contains primary and secondary coils, and because of sharing the same magnetic flux change ΔΦ, based on Faraday’s law of induction, the voltage across the secondary coil equals the voltage across the primary coil multiplying by (Ns/Np), where Ns refers to the loop numbers of the secondary coil, and Np refers to the loop numbers of the primary coil.

(a) a transformer; (b) a transformer symbol (Source: Lumen Learning)

2. Energy Storage

  The energy can be stored in an inductor. When there is a current flowing through an inductor, the induced magnetic field can store energy in the inductor. Therefore, an inductor can be treated as an energy storage device. The energy stored in an inductor during a certain time t can be indicated by the following formula: As a result, the stored energy can be expressed in the form of inductance and current flow.

3. Ferrite Beads

  Although ferrite beads are classified as a kind of inductors, they are different from general inductors. Ferrite beads are composed of magnetic ferrites, while general inductors are composed of magnetic cores and coils; Ferrite beads turn AC signals to heat, while general inductors store the energy coming from AC signals then slowly release it. The impedance of ferrite beads is high at high frequency, for instance, 100Ω at 100MHz in general. Therefore, they are suitable for filtering high-frequency noise. Ferrite beads are usually used on electronics equipment such as computers, TV’s, communication devices. The equivalent circuit of a ferrite bead is an inductor and a resistor connected in series, and the value of the inductor and resistor are both proportional to the bead’s physical length.

4. Inductive Sensors

  Inductive sensors are a general application of inductors. An inductive sensor contains an LC oscillation circuit, and when any metallic object comes close to the sensor, the coil inside the oscillation circuit will sense the electromagnetic induction. The induction will then cause changes in current flow in the coil. Once the changes are being amplified and detected, the inductive sensor works. Sometimes a ferromagnetic core may be used for intensifying the sensitivity of the inductive sensor. Generally, inductive sensors are usually used as proximity sensors (proximity switches). Inductive sensors play a critical role as the smart factory becomes reality across sectors like aerospace, automotive, healthcare, pharmaceuticals, consumer electronics, warehouse automation, industrial manufacturing, and others.

The example of an inductive sensor

5. Induction Motors

  There are multiple types of motors in the market, and the ones that use electromagnetic induction to operate are called induction motors (also called asynchronous motors). When the AC supplies power to the stator of an induction motor, a magnetic field is created, then an induction electric current occurs in the rotor, after that, torque has been produced. As the AC power supply has positive and negative cycles, the polarities of the magnetic field change accordingly. Changing polarities make both the magnetic field and the rotor rotates, and the motor starts to work.

The example of an induction motors

6. Filters

  One more popular inductor application is the filtering application. Filters are used to filter the ripples which mostly come from AC components in rectifier circuits. In any filter, inductors and capacitors are the main components: inductors block AC signals, while capacitors block DC signals. There are various types of filters, such as series inductor filters, shunt capacitor filters, L-C filters, π-filters, and so on. Among them, π-filters are used very often due to their outstanding capability of filtering. A π-filter uses an inductor and two capacitors to smoothen the output voltage.

(a) The rectified output and the output after being filtered, using an ideal filter circuit to filter the output; (b) using a π-filter as the filter circuit (Source: tutorialspoint)

7. Electromagnetic Relays

  One last inductor application introduced in this article is relays. A relay has a control system (input loop) and a controlled system (output loop), works as an automatic switch; it mainly used in automatic control circuits and controls a large current system with a rather small current flow. Relays that use the principle of electromagnetic induction to control are called electromagnetic relays. An electromagnetic relay basically contains an electromagnet and a magnetic reed switch. When applying a voltage to the coils of the electromagnet, there will be current flowing through the coils, at that time, the magnetic reed switch will be closed (i.e., ON) due to electromagnetic induction. Different relays will have applications in the industries across electrical, IoT, aerospace engineering, medical, and others. Below sample is an indication of a relay. Normally the COM (Common) pin is connected to the NC (Normal Closed) pin and separated with the NO (Normal Open) pin; when the electromagnet is electrified, the COM (Common) pin will be connected to the NO (Normal Open) pin, and the switch will be ON.

The Example of an SPDT (Single Pole Double Throw) relay (Source: www.saihs.edu.tw)

Summary

  Of course, there are still a lot of inductor applications that have not been mentioned above, such as circuit tuners, signal controllers, current switching, frequency receivers, voltage stabilizers, and so on. To sum up, inductors can be applied anywhere!