Electrical Engineering ⇒ Topic : Power in an Iron-Cored Choking Coil

Power in an Iron-Cored Choking Coil

When an air-cored coil is connected to an a.c. supply, we have to supply power to meet the loss in the resistance R of the coil only. However, power P taken by an iron-cored coil has to supply :

(1) power loss in ohmic resistance i.e., I²R where R is the d.c. resistance or true resistance of the coil.

(2) the iron loss P,(i.e., hysteresis and eddy current losses)

                          P = I²R + P_i                                                                                                                                                        ......(i)

The iron loss can be thought as additional resistance in series with the resistance of the coil.

Thus the effect of iron core is to increase the effective resistance of the coil. We can say that input to an iron-cored coil is I² R_eff i.e.,