Electronic circuits and components
Inductor specifications normally include the value of inductance (expressed in H, mH, μH, or nH), the current rating (i.e., the maximum current which can be continuously applied to the inductor under a given set of conditions), and the accuracy or tolerance (quoted as the maximum permissible percentage deviation from the marked value). Other considerations may include the temperature coefficient of the inductance (usually expressed in parts per million, ppm, per unit temperature change), the stability of the inductor, the d.c. resistance of the inductor windings (ideally zero), the Q-factor (quality factor) of the inductor, and the recommended working frequency range.
Due to manufacturing tolerances, an inductor marked with a value of 100mH will not usually have a value of precisely 100mH. For example, an inductor marked 100mH and produced with a tolerance of ±10% will have a value which falls within the range 90mH to 110mH.
Inductors are usually produced with tolerances of ±5%, ±10% or ±20% but the tolerance rating is often not marked on the body of the inductor.
All inductors have a maximum current rating which specifies the maximum continuous current that can be safely applied to the component. Exceeding this rating can have serious consequences as the insulation between windings may break down due to excessive temperature rise. Typical current ratings are 100mA, 1A, 2.5A and 10A