Introduction to Inductance and Inductors

The inductance is the key parameter that remains always ambiguous in electrical and electronics circuits. It is one of the basic measurements like resistance and capacitance which exhibits some effects in all circuits.  Inductance is employed in the field of electrical and electronic circuits and systems. Inductance is available in different forms and also, names such as coil, chokes, inductor, and transformers. These components are available with or without core and the core materials may be of various types. By acquiring knowledge on the basic concept of inductance and inductors, it is possible to get more understanding of the operation of electrical circuits and machines. In this article, we are going to see the fundamental concept of inductance ad inductors in detail.

The inductance is a term introduced by Oliver Heaviside in 1886 and the physicist Heinrich Lenz made it compulsory to denote inductance by the symbol L, in the electrical equations and the unit of inductance is Henry (H).

A coil of wire is looped around an iron core or nonmagnetic core. When a current is flowing through the coil a magnetic flux is established and the resultant magnetic field can store energy which is circulated inside the electric and magnetic circuit formed by the inductor. Many electrical apparatus is made up of a coil of wires. In transformers, two coils are wound with number of turns around the core. All electrical motors consist of stator and rotor which comprises a fixed coil and moving coil respectively. The motors and transformers are extensively used in electric power systems which makes it inductive in nature.

Basics of Inductance

Inductance is the ability to accumulate energy in the form of a magnetic field which is induced due to the flow of electric current. Inductance does not dissipate energy in the form of heat like resistance. The opposing voltage produced by the inductor is directly proportional to the change of current flow with respect to time. The inductance can be used in two ways, namely self and mutual inductance. The self-inductance is the property of coil in which the change in current in one coil induces a change in voltage of the same coil due to the effect of the magnetic field caused by the flow of current. Whereas, the mutual inductance is the inductive effect in which a change in the current of one coil induces a change in voltage in another coil due to the resultant magnetic field that links both coils. This concept is used in transformers.

The inductance of an electric circuit can be of 1 Henry if the rate of change of current in one circuit is 1 Ampere in 1 second.  A time-varying magnetic field is established if an alternating current is flowing through a coil. When the magnitude of the field is increased continuously, it stores the energy given by the electric circuit. Also, if the field gets collapsed, the stored energy is released to the electric circuit again. In a 60Hz, system this increase or collapse in the field will happen 120 times per second.

Effects of Inductance

Whenever an alternating current is flowing through the inductor, the resulting magnetic field will be changing due to the nature of the ac waveform. As a result of changing the magnetic field, an induced emf will be generated.  If the resistance of the coil is low, the current will be allowed with little loss. However, it provides a high impedance to high-frequency signals. In an ac circuit, the angle by which the current lag the voltage is purely dependent on the amount of inductance present in the circuit. The cosine of the angle between the voltage and current is denoted as the power factor of the circuit. Due to the presence of an inductor in the circuit, the current lags the voltage by 90°.

Inductors

The inductor consists of a coil enclosed around a high permeability core. The current flow over a coil produces magnetic fields. The established magnetic fields do not want to change. Thus, an inductor is a device that prevents the current changes through it. By maintaining the current that flows over the circuit as constant, the inductor does not oppose it and will not produce any forces on the charged particles curving through it. In this case, the inductor will perform just like a standard wire. Alternatively, if the current over the inductor is interrupted, the inductor will produce a force that tries to maintain the constant current. The property that opposes the flowing current in any material is called resistance. In any circuit, if the amount of resistance is larger than the current flow will decay to zero instantly. However, the current flow will decay slowly, if the inductance of the circuit is larger.

Whenever an inductor is connected to the circuit, initially it will produce a force that tries to prevent the increase of current through it. However, the current will increase slowly. The current will be increased faster if the inductance of the inductor is smaller. Once the increase of the current is stopped and obtained a steady-state value, the inductor not at all engenders a force.

Electrical Parameters of an Inductor

The induced voltage in the inductor depends upon the amount of current changes with respect to time. According to Lenz’s law, the direction of induced emf always opposes the cause of the production of it. Thus, the increase or increase in the magnitude of induced emf will be proportional to the current changes over the coil. As the ideal inductor is having no resistance ad hence, the power dissipated in the coil is zero. From the above discussion, it can be concluded that the net power loss in the coil is zero for an ideal inductor. Whenever power flows into the inductor, it is said that the energy gets stored in the inductor. The value of instantaneous power may be less than or greater than zero, depending on whether the current through the inductor is decreasing or increasing respectively.

Thus, the basic concept of inductance and inductors has been explained. The inductors are very simple device and still, it is very useful in the field of electric circuits and machines.