How Inductors Work?
How Inductors Work?
An inductor is a passive electronic component that can store electrical energy in the form of magnetic energy. It uses a conductor that is wound into a coil, and when electricity flows into the coil from the left to the right, this will generate a magnetic field in the clockwise direction and vice versa.
Inductor Symbols
What is AC Inductance?
In an alternating current circuit, which contains an AC Inductance, the flow of current through an inductor behaves very differently to that of a steady-state DC voltage. Now in an AC circuit, the opposition to the current flowing through the coils windings not only depends upon the inductance of the coil but also the frequency of the applied voltage waveform as it varies from its positive to negative values.
The actual opposition to the current flowing through a coil in an AC circuit is determined by the AC Resistance of the coil, with this AC resistance being represented by a complex number. But to distinguish a DC resistance value from an AC resistance value, which is also known as Impedance, the term Reactance is used.
Like resistance, reactance is measured in Ohm’s but is given the symbol “X” to distinguish it from a purely resistive “R” value and as the component in question is an inductor, the reactance of an inductor is called Inductive Reactance, ( XL ) and is measured in Ohms. Its value can be found from the formula.
Inductive Reactance
Where:
- XL = Inductive Reactance in Ohms, (Ω)
- π (pi) = a numeric constant of 3.142
- ƒ = Frequency in Hertz, (Hz)
- L = Inductance in Henries, (H)
We can also define inductive reactance in radians, where Omega, ω equals 2πƒ.
So whenever a sinusoidal voltage is applied to an inductive coil, the back emf opposes the rise and fall of the current flowing through the coil and in a purely inductive coil which has zero resistance or losses, this impedance (which can be a complex number) is equal to its inductive reactance.
Measuring an Inductor
The working behavior of an inductor poses an interesting question – how do we quantitatively measure the behavior of an inductor in easily measurable terms?
We could try measuring inductors by the magnetic field that they create. As soon as we do that, we run into problems. The magnetic field created by an inductor depends on the current that passes through it, so even a small inductor can create a large magnetic field.
Instead, we could use the same approach we used for capacitors, and we can define the inductance of a circuit as the voltage change induced when the current changes at a certain rate.
Mathematically,
V = L(dI/dt)
Where V is the voltage, L is the inductance, I is the current, and t is the time period.
Inductance, ‘L’, is measured in Henrys, named after Joseph Henry, the American scientist who discovered electromagnetic induction.
The formula for calculating the inductance of a coil of wire is given by this formula:
L =(µn2a)/l
Where L is the inductance in Henrys, µ is the permeability constant, i.e. a coefficient of how easily the magnetic field can be created in each medium, n is the number of turns, a is the area of the coil and l is the length of the coil.
Again, the Henry is a very large unit, so practically inductors are measured in microHenrys, uH, which is a millionth of a Henry, or milliHenrys mH, which is a thousandth of a Henry. Occasionally you might even find very small inductances measured in nanoHenrys, which are a thousandth of a uH.
Uses of Inductor?
Inductors are used in tuning circuits
The tuning circuits will pick the appropriate frequency with the aid of the inductors. Forms of capacitors, coupled with the inductor, are used in numerous electronic tools, such as radio tuning circuits, tv, to adjust the frequency and to help pick different frequency channels.
The inductive proximity sensors are very accurate in service and are a contactless system. Inductance is the fundamental concept behind it, in which the magnetic field in the coil is related to the surge of electrical current. The proximity sensors mechanism is used in traffic lights to detect the traffic density.
It is also used to store energy in a device
Inductors will retain electricity for a brief amount of time as the electricity collected as a magnetic field will vanish as the power source is withdrawn. Uses with inductors can be used in device systems where power supplies can be transferred.
Inductors are used in induction motors
In induction motors, the shaft in the engine can rotate due to the influence of the magnetic field generated by the alternating current. The speed of the engine can be calculated by the frequency of the power supply from the source. The speed of the engine can be regulated using inductors.
It is used as transformers
The association of several inductors with a common magnetic field may be converted. Most of the key applications of the transformer can be used in power transmission networks. These are used to decrease or maximize the transfer of power as step-down or step-up transformers.
Power in an Inductor
An inductor stores energy in its magnetic field when there is current through it. An ideal inductor (assuming no winding resistance) does not dissipate energy; it only stores it. When an ac voltage is applied to an ideal inductor, energy is stored by the inductor during a portion of the cycle; then the stored energy is returned to the source during another portion of the cycle. There is no net energy loss in an ideal inductor due to conversion to heat. Figure 14-36 shows the power curve that results from one cycle of inductor current and voltage.
Instantaneous Power (p)
The product of y and I give instantaneous power, p. At points where v or I is zero, p is also zero. when both v and i are positive, p is also positive. When either y or I is positive and the other negative, p is negative. When both v and i are negative, p is positive. The power follows a sinusoidal-shaped curve. Positive values of power indicate that energy is stored by the inductor. Negative values of power indicate that energy is returned from the inductor to the source. Note that the power fluctuates at a frequency twice that of the voltage or current as energy is alternately stored and returned to the source.
True Power (Ptrue)
Ideally, all the energy stored by an inductor during the positive portion of the power cycle is returned to the source during the negative portion. No net energy is consumed in the inductance, so the true power is zero. Actually, because of winding resistance in a practical inductor, some power is always dissipated; and there is a very small amount of true power, which can normally be neglected.
Reactive Power (PR)
The rate at which an inductor stores or returns energy is called its reactive power,” P", with the unit of VAR (volt-ampere reactive). The reactive power is a non zero quantity, because at any instant in time, the inductor is taking energy from the source or returning energy to it. Reactive power does not represent an energy loss due to conversion to heat. The following formulas apply: