Analysis of electric and magnetic fields leaking from induction heaters

Results are presented of an investigation on electric and magnetic fields leaking from inductive (magnetic) heaters that are used for thermal processing of high-power electron tubes and lasers in an industrial plant. Measurements of electric and magnetic fields were done using both commercially available and laboratory-developed instrumentation. Isotropic H-field sensors were developed to allow quantitative evaluation of high-intensity magnetic fields. Ten induction heaters with nominal A.C. power ranging from 2.5 kW to 15 kW and operating at frequencies between 300 kHz and 790 kHz were surveyed. Electric field strengths up to 8 kV/m and magnetic field strengths up to 20 A/m were measured.