What are the electrical characteristic parameters or quality reliability tests related to inductors? What are the definitions of the parameters? What are the purposes of the tests?

  • Inductance (L) and the drop caused by DC bias current:
    “Inductance” is the ratio of voltage to current-time gradient. (e = Ldi/dt) The purpose of measurement is to check permeability (μ), size, integrity of core and coil turn. The purpose of applying DC bias current is to check magnetic saturation characteristic of core.
  • Quality factor (Q):
    “Quality factor” is the ratio of inductive reactance (X) to alternating-current resistance (ACR). (Q = X/ACR) About the purpose of measurement, please refer to “inductance” and “alternating-current resistance”.
  • Direct-current resistance (DCR):
    “Direct-current resistance” is the resistance of copper wire. The purpose of measurement is to check soldering, wire material, coil turn, wire length, and wire breaking.
  • Alternating-current resistance (ACR):
    “Alternating-current resistance” is the equivalent resistance including not only copper wire resistance but also hysteresis and eddy current losses. The purpose of measurement is to check copper wire and hysteresis, insulation characteristics of core material.
  • Impulse winding test:
    “Impulse winding test” is a reliability test by analyzing the decay waveform caused by applying an unharmful, rapid, and low-energy impulse voltage across wound components. The purpose of test is to check lacquer and insulation material between turns and layers for detecting insulation fault.