Hong S., Joo J., Lee J.

In this paper we investigated the twice line frequency noise include it¡¯s harmonics (2f noise) from the home air conditioner using capacitor running single phase induction motor. The 2f noise is very annoying sound because of it¡¯s low frequency nature. Especially, if it occurs in small closed volume such as a bed room or meeting room, it even should make standing wave inside the room. First, from an analytical study for electrical motor driving mechanism, we found the source of 2f vibration is an unbalanced electrical force between main and sub coil of induction motor. And second, to find a correlation between this unbalanced electrical force of motor and 2f noise of air conditioner, an experimental study has been carried out. As a result, a liner correlation between the unbalanced electrical force and the 2f noise has been observed so that we proved the unbalanced electrical force is a main source of the 2f noise of air conditioner. Finally we found the unbalanced electrical force should be controlled below certain level in order to reduce the 2f noise down to applicable level for home application such as air conditioner.