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Home Excitation Characteristics of IronCore Reactors Effect of Air Gaps Air Gap and Wave Form  
See also: Correction for Fringing at Short Air Gaps  
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Air Gap and Wave Form
The introduction of an air gap in a given iron circuit increases the fundamental component I_{mag1} in Fig. 59 without appreciably affecting the coreloss current I_{c} or the component (I_{mag}  I_{mag1}) in the magnetizing current resulting from the harmonics. Thus, the fundamental component is increased without increasing the harmonics, a condition that leads to a more nearly sinusoidal wave form for the exciting current. If the increase in the fundamental component of the magnetizing current produced by the air gap is I_{air}, Eq. 547 becomes
Figure 513 shows the components of exciting current I_{iron} for the iron, I_{air} for the air gap and the total exciting current I_{(iron + air)} in a reactor or transformer with an iron core containing an air gap. The induced emf e and the flux Φ are both sinusoidal. The total exciting current I_{(iron + air)} has a better wave form than the exciting current for the iron alone. It is important to note that the airgap component current is in phase with the flux wave and is therefore also in phase with the fundamental harmonic of the magnetizing component in the exciting current required by the iron alone. Therefore, the magnetizing current I_{air} for the air gap adds directly to the fundamental harmonic I_{mag1} as indicated in Eq. 578.


Home Excitation Characteristics of IronCore Reactors Effect of Air Gaps Air Gap and Wave Form 