Frequency is the number of vibrations occurring in the time unit of one second. The formula symbol is ‘f’ and the unit of measure Hertz (Hz). The mains frequency in Europe is 50 Hz, while some power supply networks overseas operate at a frequency of 60 Hz. Frequencies above 60 Hz are referred to as medium frequencies. Normal operating frequencies for induction furnaces are:
70 Hz, 95 Hz, 150 Hz, 250 Hz, 500 Hz, 750 Hz, 1,000 Hz, 2,000 Hz and more rarely higher frequencies such as 3 kHz, 4 kHz, 5 kHz and 10 kHz for very small furnaces and inductive heating for forging or hardening.