B-field Exposure From Induction Cooking Appliances 6
2 Introduction
2.1 Background
Induction cooking has gained popularity since its introduction in the 1980s. It combines the
advantages of traditional gas and electric cooking, i.e., fast heat adjustment, precise cooking
temperature control and a glass-ceramic cooking top, allowing easy and fast cleaning. Addition-
ally, the surroundings of the hob barely heat up, thus minimizing the risk of burning. However,
this also allows a person to stay in the vicinity of the cooking area, where the magnetic flux
density can have large values because of the proximity to the current coils.
Induction cookers generate strong magnetic fields by passing an alternating current (frequen-
cies typically a few tens kHz) through the coils in the hob. When magnetic-material pans are
placed on the hob, the magnetic field generates heat in the ferromagnetic cooking vessel due to
magnetic hysteresis and induced eddy currents.
Devices emitting electromagnetic fields (EMF) are present in our living environment in ever
increasing numbers. This stimulates public concern about possible health effects due to exposure
to EMF. Safety concerns about exposure to magnetic stray-fields have arisen, since the fields
from the induction cooker cannot be fully shielded and are induced in the close vicinity of the
user (e.g., pregnant cook).
Studies by Suzuki and Yamazaki have assessed the magnetic fields with opposite findings.
Suzuki [1] reported that the maximum induced currents (numerical dosimetry) in the vicinity
of an induction cooker did not exceed the basic restrictions provided by ICNIRP [2]. However,
in a recent publication, Yamazaki [3] assessed the magnetic field from an induction cooker hob
(1.3 kW) and reported B-field values exceeding the ICNIRP guidelines: B-fields (rms-value)
greater than 14µT were measured for the fundamental frequency of 26.1 kHz, whereas the IC-
NIRP derived limit (general public exposure, 3 to 150 kHz) is only 6.25µT [2].
2.2 Objective
The objective of this study was to assess the exposure that arises during use of induction cooking
devices. This was achieved by the detailed evaluations of three devices currently available on
the Swiss market (one portable and two built-in appliances):
• First, the B-field exposure was assessed according to the European Norm EN50366 [4].
• Secondly, the worst-case field distributions were determined through measurements with
combinations of pots and pans of different sizes, shapes, and materials in single and multi-
hob use.
• Third, the adherence of the compliance procedure of the European Norm EN50366 to the
basic restrictions of ICNIRP were discussed.
