The noise and vibration during the heating are getting louder compare to when it was new.

Rust and/or dust on the polished face of I-type core and the main core cause the abnormal vibration and loud noise. Always eliminate the dust and apply the grease on the polished face of I-type core and the main core. I-type core consists of multiple thin, fragile layers of electrical steel sheets that maybe damaged if dropped or exposed to equivalent mechanical shock.