Date: 10-Sep-03 FAX COMMUNICATION B-Field Exposure From Induction Cooking No.
B-field Exposure From Induction Cooking Appliances 1 2 Executive Summary Induction cooking uses the fact that alternating magnetic fields generate heat in the ferromagnetic cooking vessel due to magnetic hysteresis and induced eddy currents. Safety concerns about exposure to magnetic stray-fields have arisen. Studies by Suzuki [1] and Yamazaki [3] have assessed these magnetic fields with contradicting findings.
B-field Exposure From Induction Cooking Appliances 3 Figure 1: a) Comparison between the compliance value (B-field measured according to EN50366) and the maximum B-field measured in the worst-case scenarios at 1 cm and 30 cm of Appliance 3. b) B-field measured according to EN50366 and c) B-field measured in the worst-case appliance (horizontal plane at height of appliance).
B-field Exposure From Induction Cooking Appliances 4 Contents 1 Executive Summary 2 2 Introduction 2.1 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2 Objective . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 6 6 3 Experimental Setup 3.1 Setup Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2 Induction Cookers . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2.
B-field Exposure From Induction Cooking Appliances 9 Acknowledgments 5 73
B-field Exposure From Induction Cooking Appliances 2 6 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. Additionally, the surroundings of the hob barely heat up, thus minimizing the risk of burning.
B-field Exposure From Induction Cooking Appliances 3 7 Experimental Setup 3.1 Setup Design In order to find and evaluate the worst-case B-field exposure that arises during the realistic use of induction cookers, the experimental setup shown in Figure 2 has been implemented. It consists of: • Three induction cooking appliances currently available on the Swiss market (winter 2005/06): one portable and two built-in devices.
B-field Exposure From Induction Cooking Appliances 8 Figure 2: Experimental setup to assess the B-field exposure. The Narda probe ELT-400 is attached on the DASY4 robot system, and the induction cooking appliance is mounted on a wooden support.
Model 68001K-in GK58TCi ETPI5640 ELDIG HOB V00 E775501 CI 261 110 GK46TI VI 411-110 AEG Electrolux Bauknecht IKEA Siemens Gaggenau V-Zug Gaggenau Inducs Inducs Inducs SH/BA 3500 SH/BA 5000 SH/DU/BA 5000 portable induction cookers KM492 SIR60FB Miele Fors built-in induction cookers Manufacturer Brand 3.5 5.0 5.0 (3.5) (2.5) 1.7 (2.5) 1.7 (2.5) 1.4 (1.9) 1.4 2.2 (3) 2.2 (3) 1.8 (2.3) 1.4 Front-left 5.0 - (1.8) 2.2 (3.3) 2.2 (3.3) 1.4 (1.9) 1.8 1.8 (2.3) 1.8 (2.3) 1.4 1.8 (2.
B-field Exposure From Induction Cooking Appliances 10 In Table 1, the maximum rated power of each hob is given without and with the booster function for each model. The total power of the appliance is also provided (sum of the specified maximum power of each hob without booster). The booster function permits the application of additonal power to a specific hob, with the limitation that not all hobs are available for use; otherwise the maximum rated power would be exceeded.
B-field Exposure From Induction Cooking Appliances 11 Figure 3: Selected induction cookers. a) appliance 1: Electrolux GK58TCi, b) appliance 2: Gaggenau CI 261 110, and c) appliance 3: Inducs SH/BA 5000. Figure 4: Top view, dimensions (in mm) and coordinate system for a) appliance 1 (Electrolux) and b) appliance 2 (Gaggenau).
B-field Exposure From Induction Cooking Appliances 12 Figure 5: Dimensions (in mm) and coordinate system of appliance 3 (Inducs), top view and side view. Figure 6: The hobs 1 to 4 correspond, respectively, to the front-left, front-right, rear-left and rear-right hobs. The front, rear, left and right sides of the appliance are indicated, as well as the measuring distance and probe-center/hob-center distance.
B-field Exposure From Induction Cooking Appliances 13 Figure 7: Dimensions of the wooden supports (in mm): a) appliances 1 (Electrolux) and 2 (Gaggenau), and b) appliance 3 (Inducs). Figure 8: Induction cookers with wooden supports: a) appliance 1 (Electrolux), b) appliance 2 (Gaggenau) and c) appliance 3 (Inducs). 3.3 Pots and Pans The B-field exposure has been assessed for several new and used pots and pans of different sizes and shapes, as well as various materials. These are depicted in Figure 10.
B-field Exposure From Induction Cooking Appliances 14 is 12 cm without specification of pot thickness. The Electrolux manual (appliance 1) specifies a bottom thickness of 2 to 3 mm for enameled steel pots, and 4 to 6 mm for stainless steel pots, without specification of minimal pot diameter. Instructions concerning suitable pots and pans are given in the manuals of all appliances: • Only ferromagnetic pans are suitable for induction cooking.
B-field Exposure From Induction Cooking Appliances 15 Figure 10: Pans, frying-pans and pots used during the experiments to define the worst-case set of pots.
Description frying-pan small saucepan large pot saucepan, bottom not flat non-paramagnetic Saucepan large enameled pot small enameled pot small enameled pot wok cast-iron pot small pot small pot large pot small pot medium pot medium pot Pot 1 2 3 4 5 6 7 8 9 10 11a 11b 12 13 14a 14b IKEA IKEA IKEA 2nd hand 2nd hand 2nd hand 2nd hand 2nd hand 2nd hand Migros Migros Migros Migros IKEA IKEA IKEA shop shop shop shop shop shop Manufacturer / Distributor stainless steel, aluminum stainless steel, aluminum st
appliance 3 (Inducs) hob measuring distance [mm] dist. probe/hob center [mm] measuring distance [mm] dist. probe/hob center [mm] appliance 2 (Gaggenau) hob measuring distance [mm] dist. probe/hob center [mm] measuring distance [mm] dist. probe/hob center [mm] appliance 1 (Electrolux) hob measuring distance [mm] dist. probe/hob center [mm] measuring distance [mm] dist. probe/hob center [mm] 542.5 252.5 1 512.5 222.5 1 front side 1 10 322.5 300 612.5 front side 2 3 10 262.5 462.5 300 552.5 752.
B-field Exposure From Induction Cooking Appliances 18 Worst-case set of pots A worst-case set of pots has been selected (see Figure 11), composed of pots 8, 7, 13 and 2 with bottom diameters of 14 cm, 14 cm, 14.5 cm and 15 cm, respectively. Figure 11: Worst-case set of pots. 3.4 B-field Narda Sensor ELT-400 The magnetic flux density (B-field) was measured using the Narda exposure level tester ELT-400 (see Figure 12). Figure 12: Narda exposure level tester ELT-400.
B-field Exposure From Induction Cooking Appliances 19 The measurement time interval is 250 ms. The rms-value, given in [µT], is continuously integrated over four intervals, and the integration time of the rms calculation is fixed at 1 s. The Narda ELT-400 probe can also operate as an active probe, using the three separate, analog signals corresponding to the three spatial axes x, y, and z. Connecting it to an external oscilloscope or spectrum analyzer allows temporal and spectral measurements.
B-field Exposure From Induction Cooking Appliances 4 4.1 20 Evaluation of Measurement System Sensor Characterization Helmholtz coil The uncertainty of the Narda instrument was evaluated using the Helmholtz coil, designed to test the T-coil compatibility of mobile phones (ANSI63.19). It is comprised of a pair of identical circular magnetic coils (diameter 284.8 mm) that are coaxially aligned and separated by a distance equal to the radius of the coil. Each coil carries an equal electrical current.
B-field Exposure From Induction Cooking Appliances 21 4 µ0 N I B = ( )3/2 (5) 5 R The generated B-fields in the Helmholtz coil are 8.6 µT and 0.86 µT when applying Vout = 10 Vpp and 1 Vpp (peak-to-peak), in the frequency range corresponding to a flat response. Frequency response The specifications of the Narda probe ELT-400 indicate a flat frequency response for the frequency range from 30 Hz to 400 kHz. To validate this, the experimental setup shown in Figure 15 was used.
B-field Exposure From Induction Cooking Appliances 22 from those two measurements. As given in the specifications, the cut-off frequencies for the Narda probe ELT-400 are around 30 Hz and 400 kHz, and the frequency response is flat between those frequencies; the error is smaller than ±0.8 dB. The error in [dB] was calculated using the Equation (6): Error[dB] = 20 log(B/Baverage ) (6) Figure 15: Spherical isotropy of the Narda probe ELT-400.
B-field Exposure From Induction Cooking Appliances 23 Spherical isotropy The experimental setup shown in Figure 15 f) was used to evaluate the spherical isotropy of the Narda probe ELT-400. The probe rotates around its vertical z-axis, and the B-field is measured as a function of the probe angle of rotation (from -180◦ to 180◦ ). The measurements are performed on the top and at the side of the Helmholtz coil (see Figure 15 e) ).
B-field Exposure From Induction Cooking Appliances 4.2 4.2.1 24 Time- and Frequency-Domain Characterization of the Induction Cookers Time-Domain Characterization Measurements The alternating magnetic fields generated by the induction cookers were measured with the Narda probe ELT-400. The analog output signals of the probe were recorded with a digital oscilloscope (Agilent 54622D mixed signal oscilloscope).
B-field Exposure From Induction Cooking Appliances 25 Figure 18: Time-domain signals of the alternating magnetic field generated by appliance 2. Graphs a) and b) correspond to the heat settings 4 and P. The fundamental signal frequencies are, respectively, 52.1 kHz and 21.2 kHz. The signal rms-value increases approximately by a factor of 2.5 for heat settings from 4 to P.
B-field Exposure From Induction Cooking Appliances 26 Figure 19: Time-domain signals of the alternating magnetic field generated by appliance 3. Graphs a) and b) correspond to the heat settings 4 and 12. The fundamental signal frequencies are 62.7 kHz and 21.7 kHz, respectively. The signal rms-value increases approximately by a factor of 4 for heat settings from 4 to 12.
B-field Exposure From Induction Cooking Appliances 27 Table 5: Signal and envelope modulation frequency of appliances 1, 2 and 3 for the heat settings 4 and P or 12. heat setting appliance 1 appliance 2 appliance 3 signal frequency [kHz] 4 P or 12 42 18 52 21 63 22 envelope frequency [Hz] 4 to max. (P or 12) 100 100 300 pulse-width modulation frequency [Hz] 1 to 4 0.5 0.5 0.
B-field Exposure From Induction Cooking Appliances 28 Figure 20: Dependency of the signal frequency on the heat setting. Graphs a), b) and c) correspond to appliances 1, 2 and 3, respectively. harmonics is calculated for appliances 1, 2 and 3 in Tables 7, 8 and 9, respectively. These Tables show that the contribution in terms of power of all harmonics does not exceed 1 %, 2.5 % and 1.8 % of the fundamental signal for appliances 1, 2 and 3, respectively.
B-field Exposure From Induction Cooking Appliances 29 Table 7: Appliance 1, Calculated harmonics contribution in [%], in terms of power. Heat setting Fundamental frequency f [kHz] 3f 5f 7f Contribution of the 9f harmonics [%] 11f 13f 15f 17f 19f Total in terms of power [%] P p J ∝ i i Pif [%] 4 41.7 0.8 0.08 0.03 0.006 0.916 5.91 5 33.0 0.5 0.05 0.02 0.008 0.003 0.581 4.93 6 28.8 0.5 0.06 0.01 0.006 0.003 0.0016 0.5806 4.88 7 24.0 0.4 0.05 0.01 0.004 0.003 0.0016 0.0008 0.4694 4.37 8 22.5 0.3 0.04 0.
B-field Exposure From Induction Cooking Appliances 30 Figure 21: Harmonics contribution, in [dB] (power spectrum, 10 dB per division). Graphs a) and b), c) and d), e) and f) correspond to appliances 1, 2 and 3, with hobs 1, 2 and 1, respectively (largest hobs). Figure 22: Measured B-field exposure for different heat settings, for a) appliance 1, b) appliance 2 and c) appliance 3.
B-field Exposure From Induction Cooking Appliances 4.3 31 Uncertainty Budget Table 10 gives a list of probable sources of error and an evaluation of the uncertainty budget, as given in the IEEE 1528-2003 standard [9]. The uncertainty was assessed in the region of the test specification limit (6.25 µT) and for the full range of measurements.
B-field Exposure From Induction Cooking Appliances 32 Table 10: Measurement uncertainty evaluation. As described in IEEE 1528-2003, the tolerance, the probability distribution (R = Rectangular distribution), the divisor used to get standard uncertainty, the sensitivity coefficient ci , the uncertainty components ui and the combined standard uncertainty uc are given.
B-field Exposure From Induction Cooking Appliances 5 33 Assessments According to EN50366 conditions One objective of this study was to measure whether the B-field exposure from the three selected induction cookers complies with the derived and basic restrictions of the ICNIRP guidelines, when assessed according to the European Norm EN50366. 5.0.
B-field Exposure From Induction Cooking Appliances 34 diameters of standard cooking vessels are: 110 mm, 145 mm, 180 mm, 210 mm and 300 mm. The hobs are operated in turn at the highest power setting, with all other cooking zones uncovered. The measurements are made after stable operating conditions have been reached. If no stable conditions can be reached, an appropriate observation time (e.g., 30 s) shall be defined to be sure to get the maximum value with fluctuating field sources.
B-field Exposure From Induction Cooking Appliances 35 Figure 24: Appliance 1, single-hob measurement using the standard set of pots (front and rear sides of the appliance). Graphs a) to d) correspond to front side B-field measurements along the z-axis, in front of a) hob 1, b) hob 2, c) hob 3 and d) hob 4, at measuring distances of 1, 5, 10 and 30 cm.
B-field Exposure From Induction Cooking Appliances 36 Figure 25: Appliance 1, single-hob measurement using the standard set of pots (left and right sides of the appliance). Graphs a) to d) correspond to left side B-field measurements along the z-axis, in front of a) hob 1, b) hob 2, c) hob 3 and d) hob 4, at measuring distances of 1, 5, 10 and 30 cm.
B-field Exposure From Induction Cooking Appliances 37 Figure 26: Appliance 2, single-hob measurement using the standard set of pots (front and rear sides of the appliance). Graphs a) to d) correspond to front side B-field measurements along the z-axis, in front of a) hob 1, b) hob 2, c) hob 3 and d) hob 4, at measuring distances of 1, 5, 10 and 30 cm.
B-field Exposure From Induction Cooking Appliances 38 Figure 27: Appliance 2, single-hob measurement using the standard set of pots (left and right sides of the appliance). Graphs a) to d) correspond to left side B-field measurements along the z-axis, in front of a) hob 1, b) hob 2, c) hob 3 and d) hob 4, at measuring distances of 1, 5, 10 and 30 cm.
B-field Exposure From Induction Cooking Appliances 39 Figure 28: Appliance 3, with pot 3 (large pot, standard set of pots). The B-field is measured along the z-axis, on the a) front side, b) rear side, c) left side and d) right side of the appliance using pot 3 at measuring distances of 1, 5, 10 and 30 cm. The other measuring conditions were according to EN50366 with the pot centered on the hob. Figure 29: Appliance 3, with pot 13 (small pot, standard set of pots).
B-field Exposure From Induction Cooking Appliances 6 41 Worst-Case Exposure Conditions for Varied Loading of the Induction Cookers The influence of several parameters was evaluated to assess the worst-case exposure. 6.0.6 Predominant Parameters Pot-hob centering The predominant parameter is the centering of the pot on the hob. The B-field measured at a fixed position of the probe is minimal for perfect centering.
B-field Exposure From Induction Cooking Appliances 42 Figure 31: Influence of pot characteristics (bottom diameter, shape, bottom flatness and material grade) on the B-field measured. a) Normalized B-field measured for each pot (pots ranked from smallest to largest bottom diameter). b) Standard set of pots; the measured B-field decreases when the bottom diameter increases. c) For four pots with the same bottom diameter, the B-field measured depends on the pot characteristics (material, flatness).
B-field Exposure From Induction Cooking Appliances 43 Figure 32: Influence of the volume of water and the duration of measurements on the B-field measured, a) appliance 1, b) appliance 2, and c) appliance 3. For each appliance, pot 3 (large pot, standard set of pots) is centered on the largest hob (hobs 1, 2 and 1 for appliances 1, 2 and 3, respectively). The pot is initially filled with 3 l of tap water. Measuring distance of 1 cm, heat setting 8.
B-field Exposure From Induction Cooking Appliances 44 a factor of 4 when using a lid, allowing longer measurement times, while maintaining constant measuring conditions. A lid was used for all of the DASY4 robot measurements. Handle position In the case of frying-pan and saucepans, the handle position has a noticeable influence on the B-field exposure. However, no general rule could be established, and the variation of the B-field depends strongly on the pot, hob and appliance combination.
B-field Exposure From Induction Cooking Appliances 45 Table 12: Standard scenarios (using the standard set of pots) defined to measure the B-field emitted by the 3 induction cookers using the DASY4 robot system. Single-hob measurement Multi-hob measurement Appliance 1 2 3 3 1 1 2 Hob(s) 1 to 4 1 to 4 1 1 1 2 3 4 1 3 1 2 3 4 Pot(s) 3, 14a, 14b, 13 3, 14a, 14b, 13 3 13 3 14a 14b 13 3 14a 14a 3 14b 13 Heat setting P P 12 12 P P 8 7 P P 9 9 9 9 App.
B-field Exposure From Induction Cooking Appliances 46 hob use, and pan centered and not. The worst-case exposure depends on the combinations of pot/hob/appliance. The pots for the worst-case scenarios where chosen experimentally. Figure 34: Localization of the pots during standard and worst-case, single- and multihob measurements: a) and d) appliance 1, b) and e) appliance 2, c) and f) appliance 3. 6.1.
B-field Exposure From Induction Cooking Appliances 47 Multi-hob measurement using the standard set of pots Figure 36 shows the B-field measured in the vicinity of appliance 1, with hobs 1, 2, 3 and 4 switched on simultaneously (multi-hob measurement) and using the standard set of pots centered and non-centered. The B-field does not exceed the ICNIRP limit (6.25 µT) for a measuring distance of 30 cm, according to EN50366.
B-field Exposure From Induction Cooking Appliances 48 Figure 35: Appliance 1 single-hob measurement using the standard set of pots: In Graphs a) to d), the B-field is measured in the vertical plane (y, z) at the front side of the appliance, at measuring distances of a) 1 cm, b) 5 cm, c) 10 cm and d) 30 cm. In Graphs e) to h), the B-field is measured in the horizontal plane. Graphs e), f), g) and h) correspond to the front, rear, left and right sides of the appliance, respectively.
B-field Exposure From Induction Cooking Appliances 49 Figure 36: Appliance 1 multi-hob measurement (four hobs) using the standard set of pots. Comparison of the B-field when the pots are a) to d) centered, and e) to h) non-centered (front side of the appliance): The B-field is measured in the vertical plane (y, z), at measuring distances of a) 1 cm, b) 5 cm, c) 10 cm and d) 30 cm.
B-field Exposure From Induction Cooking Appliances 50 Figure 37: Appliance 1 multi-hob measurement (two hobs) using the standard set of pots (front side of the appliance): The B-field is measured in the vertical plane (y, z), at measuring distances of a) 1 cm, b) 5 cm, c) 10 cm and d) 30 cm. Hobs 1 and 3 are switched on simultaneously (multi-hob measurement), using the standard set of pots (pots 3 and 14a on hobs 1 and 3, respectively), other measuring conditions according to EN50366.
B-field Exposure From Induction Cooking Appliances 51 Figure 38: Appliance 1 single-hob measurement using the worst-case set of pots (front side of the appliance). Comparison of the B-field when the pot is a) to e) centered, and f ) to j) non-centered: In Graphs a), b), c), d), f), g), h) and i), the B-field is measured in the vertical plane (y, z) at measuring distances of 1, 5, 10, 30, 1, 5, 10 and 30 cm, respectively. In Graphs e) and j), the B-field is measured in the horizontal plane.
B-field Exposure From Induction Cooking Appliances 52 Figure 39: Appliance 1 multi-hob measurement (three hobs) using the worst-case set of pots (front side of the appliance). Comparison of the B-field when the pot is a) to e) centered, and f ) to j) non-centered: In Graphs a), b), c), d), f), g), h) and i), the B-field is measured in the vertical plane (y, z), at measuring distances of 1, 5, 10, 30, 1, 5, 10 and 30 cm, respectively. In Graphs e) and j), the B-field is measured in the horizontal plane.
B-field Exposure From Induction Cooking Appliances 53 Figure 40: Appliance 1 multi-hob measurement (two hobs) using the worst-case set of pots (front side of the appliance). Comparison of the B-field when the pot is a) to e) centered, and f ) to j) non-centered: In Graphs a), b), c), d), f), g), h) and i), the B-field is measured in the vertical plane (y, z), at measuring distances of 1, 5, 10, 30, 1, 5, 10 and 30 cm, respectively. In Graphs e) and j), the B-field is measured in the horizontal plane.
B-field Exposure From Induction Cooking Appliances 6.1.3 54 Appliance 2 Single-hob measurement using the standard set of pots Figure 41 shows the B-field measured in the vicinity of appliance 2, with hob 2 switched on using pot 3 (standard set of pots) centered (front side measurement). The B-field does not exceed the ICNIRP limit (6.25 µT) for a measuring distance of 30 cm, according to EN50366. The limit is not even exceeded at 1 cm off the edges of the appliance.
B-field Exposure From Induction Cooking Appliances 55 Figure 42: Appliance 2, multi-hob measurement using the standard set of pots, with pots centered: The B-field is measured in the vertical plane (y, z), at measuring distances of a), c), e) and g) 1 cm and b), d), f) and h) 30 cm; a) and b) front side, c) and d) rear side, e) and f) left side and g) and h) right side of the appliance.
B-field Exposure From Induction Cooking Appliances 56 Figure 43: Appliance 2, multi-hob measurement using the standard set of pots with pots non-centered (front side of the appliance): The B-field is measured in the vertical plane (y, z), at measuring distances of a) 1 cm, b) 5 cm, c) 10 cm and d) 30cm.
B-field Exposure From Induction Cooking Appliances 57 Figure 44: Appliance 2, single-hob measurement using the worst-case set of pots. Comparison of the B-field when the pot are a) to d) centered, and e) to h) noncentered (front side of the appliance): In Graphs a), b), c), d), e), f), g) and h), the B-field is measured in the vertical plane (y, z) at measuring distances of 1, 5, 10, 30, 1, 5, 10 and 30 cm, respectively. Hob 2 is switched on (single-hob measurement) using the worst-case pot 8.
B-field Exposure From Induction Cooking Appliances 58 Figure 45: Appliance 2, multi-hob measurement using the worst-case set of pots. Comparison of the B-field with the pot a) to d) centered, and e) to h) non-centered (front side of the appliance): In Graphs a), b), c), d), e), f), g) and h), the B-field is measured in the vertical plane (y, z) at measuring distances of 1, 5, 10, 30, 1, 5, 10 and 30 cm, respectively.
B-field Exposure From Induction Cooking Appliances 6.1.4 59 Appliance 3 Single-hob measurement using pot 3, large pot, standard set of pots Figures 46 and 47 depict the B-field measured in the vicinity of appliance 3 with pot 3 (large pot, standard set of pots) centered and non-centered. Figure 46 depicts the front side measurements, and Figure 47 the measurements at the rear, left and right sides of the appliance. The B-field does not exceed the ICNIRP limit (6.
B-field Exposure From Induction Cooking Appliances 60 Figure 46: Appliance 3 and pot 3 (large pot, standard set of pots), front side of the appliance. Comparison of the B-field with pot a) to e) centered, and f ) to h) non-centered: In Graphs a), b), c), d), f) and g), the B-field is measured in the vertical plane (y, z), at measuring distances of 1, 5, 10, 30, 1 and 30 cm, respectively. In Graphs e) and h), the B-field is measured in the horizontal plane. Other measuring conditions according to EN50366.
B-field Exposure From Induction Cooking Appliances 61 Figure 47: Appliance 3 and pot 3 (large pot, standard set of pots). Graphs a) to f ), g) to l) and m) to r) correspond to the rear, left and right sides of the appliance, respectively. Comparison of the B-field with pot a) to c), g) to i), m) to o) centered, and d) to f ), j) to l) and p) to r) non-centered: In Graphs a), d), g), j), m) and p), the B-field is measured along the z-axis at measuring distances of 30, 10, 5 and 1 cm.
B-field Exposure From Induction Cooking Appliances 62 Figure 48: Appliance 3 and pot 13 (small pot, standard set of pots), front side of the appliance. Comparison of the B-field with pot a) to e) centered, and f ) to h) non-centered: In Graphs a), b), c), d), f) and g), the B-field is measured in the vertical plane (y, z), at measuring distances of 1, 5, 10, 30, 1 and 30 cm, respectively. In Graphs e) and h), the B-field is measured in the horizontal plane. Other measuring conditions according to EN50366.
B-field Exposure From Induction Cooking Appliances 63 Figure 49: Appliance 3 and pot 13 (small pot, standard set of pots). Graphs a) to f ), g) to l) and m) to r) correspond to the rear, left and right sides of the appliance, respectively. Comparison of the B-field with pot a) to c), g) to i), m) to o) centered, and d) to f ), j) to l) and p) to r) non-centered: In Graphs a), d), g), j), m) and p), the B-field is measured along the z-axis at measuring distances of 30, 10, 5 and 1 cm.
B-field Exposure From Induction Cooking Appliances 64 Figure 50: Appliance 3 and pot 8 (worst-case set of pots), front side of the appliance. Comparison of the B-field with pot a) to e) centered, and f ) to h) non-centered: In Graphs a), b), c), d), f) and g), the B-field is measured in the vertical plane (y, z), at measuring distances of 1, 5, 10, 30, 1 and 30 cm, respectively. In Graphs e) and h), the B-field is measured in the horizontal plane.
B-field Exposure From Induction Cooking Appliances 65 Figure 51: Appliance 3 and pot 8 (worst-case set of pots). Graphs a) to f ), g) to l) and m) to r) correspond to the rear, left and right sides of the appliance, respectively. Comparison of the B-field with pot a) to c), g) to i), m) to o) centered, and d) to f ), j) to l) and p) to r) non-centered: In Graphs a), d), g), j), m) and p), the B-field is measured along the z-axis at measuring distances of 30, 10, 5 and 1 cm.
B-field Exposure From Induction Cooking Appliances 6.1.5 66 B-field Measurement Above the Appliances As indicated in Figure 52, the B-field was measured above the induction cookers to evaluate the exposure in the vicinity of the pot. With induction cookers, the surroundings of the hob do not heat significantly, allowing the cook to stay in the vicinity of the cooking area, where the magnetic field exposure is at a maximum.
B-field Exposure From Induction Cooking Appliances 67 Figure 53: B-field measurement above the appliances: a) and b) correspond to appliance 1, with a) pot 3 centered, b) pot 8 centered. c) and d) correspond to appliance 2, with c) pot 3 centered, d) pot 8 centered. e) to g) correspond to appliance 3, with e) pot 3 centered, f) pot 13 centered, and g) pot 8 centered. Measuring conditions are described in Chapter 6.1.1.
B-field Exposure From Induction Cooking Appliances 6.1.6 68 Discussion The evaluation according to EN50366 (i.e., for a measuring distance of 30 cm) demonstrates compliance according to the ICNIRP limit (6.25 µT) for all three devices with a margin larger than 13 dB (see Chapter 5.0.1 and Table 11). As demonstrated in this report, different pot and and heating configurations can results in exposures that well exceeds +10 dB of the standard EN50366 configurations at same distance.
Pot 3 Pot 13 Pot 8 Standard Worst-case Multi-hob Worst-case Standard Single-hob Worst-case yes no yes no yes no yes no yes no yes no yes no yes no yes no yes no yes no Pot(s) centered 3 5.5 1-5 5-10 9 15 9 15 1-5 1-5 1-5 5-10 1-5 10 12 4 19 6 20 front side [cm] 3 1-5 3-5 13-14 9-10 24-25 13-14 22-24 other sides [cm] Meas. dist. at which ICNIRP limit is exceeded 7.2 13 8.6 13 21 38 21 36 2.7 2.5 8.5 7.5 16 8.5 13.2 3.7 18 9.0 34 11.5 35 front side [µT] 8.0 14 13.5 12.5 27.
B-field Exposure From Induction Cooking Appliances 7 70 Approximation of Induced Current Density As shown in Chapters 6.1.2, 6.1.3, 6.1.4 and in Table 14, the B-fields measured around the induction cookers are largely non-uniform. The ICNIRP guidelines [2] state that the reference levels are intended to be spatially averaged values over the entire body of the exposed individual, but with the important provision that the basic restrictions on localized exposure are not exceeded.
B-field Exposure From Induction Cooking Appliances | E(t) | = πaf B0 71 (14) The induced current density J is derived from Ohm’s law: | J(t) | = πaf σB0 (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.
B-field Exposure From Induction Cooking Appliances 8 72 Conclusion The objective of this study was to assess the maximum exposure that arises during the use of induction cooking devices. Three devices currently available on the Swiss market were selected: the built-in appliances 1 and 2 (Electrolux GK58TCi and Gaggenau CI 261 110) and the portable appliance 3 (Inducs SH/BA 5000).
B-field Exposure From Induction Cooking Appliances 73 Fifteen pots and pans of different sizes and shapes, as well as of various materials were evaluated in single and multi-hob use in order to select a worst-case set of pots corresponding to the worst-case B-field exposure. A standard set of pots was also defined according to the European Norm EN50366.
B-field Exposure From Induction Cooking Appliances 74 [5] ”Household and similar electrical appliances Electromagnetic fields - Methods for evaluation and measurement,” CENELEC EN50366 prA1, 2005. [6] E. L. Bronaugh, ”Helmholtz coils for calibration of probes and sensors: limits of magnetic field accuracy and uniformity,” 1995 IEEE Symposium on EMC, Atlanta, 1995. [7] ”NIS 81,Treatment of uncertainty in EMC measurements,” Edition 1, May 1994. [8] B. N. Taylor, and C. E.
