Inductors in General

  • The characteristics such as the inductance and Q values etc. have the frequency dependence.
  • The stress from resin coating and molding could result in change of inductance.
  • The inductors use ceramic materials so, chipping and crack could occur. Please be careful of the handling. Excessive vibration and impact could destroy the parts.
  • Keep magnetic tweezers and magnets away from the inductors to avoid change of inductance caused by magnetization. Do not press the wire wound part of the chip inductor with sharp objects.
  • The Inductance could decrease according to magnetic saturation when the inductor is used exceeding the allowable current. There is also a possibility of disconnection and short-circuit or emitting smoke and ignition caused by the heat generation of the inductor.
  • There is a risk of disconnection when excessive current(inrush current) is applied. Change of the characteristics may occur by the magnetization of the core when excessive current is applied to a DC circuit.
  • When the parts are used with high-frequency, the heat generation would be larger and the part temperature gets higher compared with the DC or low-frequency. They are caused by the increasing iron loss and copper loss. Please be careful not to exceed the operating temperature range of the parts.

  • The electrical characteristics change from the variation of frequency of the parts. When the part is used above the frequency band of the SRF (self-resonant frequency), it would function as a capacitor so please do not use the parts above the SRF.


  • Some inductors have magnetic polarities.
  • When the distance between non-magnetically-shielded inductors are small, they may cause magnetic coupling so be careful of the layout of components. Please check the characteristics beforehand with the actual equipment when mounting with high density.
  • Do not place large magnetic materials such as audio speakers around the inductors.
  • Inductance and Q values may change because of magnetic coupling with the chassis and patterns etc.
  • Do not expose the inductors to the heat radiation from other high temperature parts.


  • For basic precautions, please refer to the Technical report of JEITA RCR-2501A Safety application guide for inductors for use in electronic equipment.

Nomina Inductance

  • A inductance that the inductor is designed to have and generally indicated on the body.

Quality factor

  • A coefficient that shows the quality of the inductors. It is calculated from the following formula.

Self-resonant frequency

  • Frequency that the resonance occurs by the distribution capacity and inductance of the inductor.

DC resistance value

  • Frequency that the resonance occurs by the distribution capacity and inductance of the inductor.

Allowable DC(Direct-current)

  • Upper limit of the current which is set by us to assure the safe use of the inductors.
  • It is defined as the smaller DC current value of either the DC superposition or the surface temperature rise characteristics.
  • DC superposition characteristic is a phenomenon which occurs when the inductors made with magnetic materials such as ferrite is applied large DC. When this ccurs, the inductance drops because of the magnetic saturation.
  • Surface temperature rise characteristic shows the relations between the DC value and the surface temperature rise.

Iron loss

  • Electrical energy that is lost when the wire wound magnetic material is magnetized by the applied AC. It is calculated by the sum of hysteretic loss and eddy-current loss.

Copper loss

  • Energy that is transformed into Joule heat by the resistance of the wound wire. The Copper loss increases in the highfrequency band from the skin effect.