What Is Inductor Impedance?

Inductor impedance, also known as inductive reactance, is a generalized concept of direct current (DC) and alternate current (AC) resistance to an inductor. A passive component, an inductor is designed to resist current changes. The materials and construction of an inductor determine the inductor impedance. A mathematical formula can be used to calculate the impedance value of a particular inductor.

The ability to resist current change, combined with the ability to store energy in a magnetic field are some of an inductor's most useful properties. When a current flows through a particular inductor, it will produce a changing magnetic field which can induce voltage that opposes the current produced. Induced voltage is then proportional to the current change rate and an inductance value.

An inductor can be made in many ways and with several different materials. Design and materials can both affect the inductor impedance. Inductors and their materials have specific electrical specifications that include properties such as DC resistance, inductance, permeability, distributed capacitance, and impedance. Each inductor has an AC component and a DC component, both of which have their own impedance values. A DC component’s impedance is known as the winding DC resistance, while the AC component’s impedance is called the inductor reactance.

Impedance can differ and be manipulated by the materials that make up an inductor. For example, an inductor may have two circuits that are coupled and adjusted so that one circuit’s output impedance is equivalent to the opposite circuit’s input impedance. This is called matched impedance and is beneficial because minimal power loss occurs as a result of this kind of inductor circuit setup.

Inductor impedance can be solved with a mathematical equation using angular frequency and inductance. Impedance is dependent on the frequency of a wavelength; the higher the wavelength’s frequency, the higher the impedance. In addition, the higher the inductance value, the higher the inductor impedance. The basic equation for impedance is calculated by multiplying the values “2”, “π”, “hertz” and “henries” of a wavelength. The values obtained in this equation, however, depend on other values including the ohm measurements of resistance, capacitive reactance, and inductive reactance.

Obtaining the inductor impedance requires additional calculations. Both capacitive reactance and inductive reactance are 90 degrees out-phased by resistance, which means the maximum values of both happen at different moments in time. Vector addition is used to solve this problem and calculate impedance. Capacitive reactance may be calculated by adding the squares of inductive reactance and resistance. The square root of the added values is then taken and used as the value of the capacitive reactance.