Dynamic transverse stiffness of a magnetically biased laminated iron core

It was found that the effective dynamic transverse stiffness of a laminated soft iron core is a function of magnetic bias. The effective dynamic transverse stiffness was observed by building an ultrasonic oscillator using a laminated soft iron core. The laminated core was assembled employing conventional silicon steel transformer laminations. When the core is properly excited by dc pulses, it produces ultrasonic frequency electrical oscillations in the electrical circuit and ultrasonic acoustic emission in the air through the vibrating laminated core. The oscillation frequency is tunable by adjusting the dc magnetic bias. The oscillation frequency is determined by, among other parameters, the effective dynamic transverse stiffness of the core, or the "spring constant" of the laminated core system. Ultrasonic frequencies of 9-28 kHz were generated with 100-180 gauss bias. The peak acoustic power was estimated to be 38.8 watts with a peak electrical input power of 150 watts.