of subharmonic mode of ferroresonance, the odd subharmonic modes do occur. However, the even
subharmonic oscillations also have been reported,Mork, et al. (1994).
The frequency spectrum of the subharmonic mode, Figure 5(b), demonstrates the fundamental frequency of 1/n times the power frequency. The other frequency components of the waveform depend on the odd or the even order of the subharmonic mode. If the subharmonic order n is odd, the odd harmonics of the fundamental frequency 1/n exist in the waveform. However, with the even subharmonic n, the waveform also includes the even harmonics of the 1/ncomponent. Based on n-times larger cycle than the power cycle, the subharmonic mode of the order n presents n sample points on the Poincae map, as shown in Figure 5(c).