B-field Exposure From Induction Cooking Appliances 71
| E(t) | = πafB
0
(14)
The induced current density J is derived from Ohm’s law:
| J(t) |= πafσB
0
(15)
The averaged B-field for the worst-case configuration of Appliance 3, averaged over the area
with a = 0.175m (dimensions of the numerical homogeneous human body, see [4]) at height z =
1 m, equals 18 µT (average B-field in the worst case plane). Assuming f = 20 kHz, σ = 0.2 S/m
(see [2]), the induced current density magnitude equals J = 39.6 mA/m
2
(rms) compared to
the ICNIRP basic restriction for the general public exposure at 20 kHz, which equals 40 mA/m
2
(rms). A device with similar field distributions but close to the limits at EN50366 configurations
(B=6.25 µT at a measuring distance of 30 cm, for standard measurement according to EN50366)
would induce a current density of 315 mA/m
2
, which would be 18 dB above the ICNIRP limits.
In conclusion, the ICNIRP basic restriction may be exceeded by considerable margin while
the device would be considered compliant with EN50366. Further numerical simulations are
therefore necessary to evaluate the potential of violation, especially in pregnant women.
