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Induction hob

Field description

Belongs to: Kitchenware and household appliances
Synonyms: Induction stove
Description: The heating process of an induction hob is based on inductively generated eddy currents. For that purpose, coils are placed beneath the ceramics cooking field to generate an alternating magnetic field. This alternating field induces eddy currents in the metallic cooking pot placed on top of the cooking field which is thereby heated due to its ohmic resistance. Only special cooking pots that are explicitly marked as suitable for inudction cooking can be used. Typcially, these pots are made of ferromagnetic material, such as iron, cobalt or nickel, which forces the alternating magnetic field into the outer regions of the saucepan's floor. This phenomenon known as Skin effect increases the ohmic resistance of the cooking pot and thereby enhances the cooking process. Hysteresis effects caused by the change in magnetization due to the alternating magnetic field equally contribute to the heating process. As part of alternating magnetic field cannot be picked up by the cooking pot, the position of the cooking pot on the cooking plate is decisive for both the cooking process and the exposure of the cook. For minimal cooking time and minimal exposure to magnetic fields, the pot has to be placed exactly on the designated area. Contrary to that, for a coffee pot which never fills out a cooking plate due to its lesser diameter, the optimum position for minimal exposure is generally off center.

Unless otherwise stated, the operating frequency confirms with measured frequency, i.e. the measurement was performed at the operating frequency of the induction stoves.
Frequency ranges:
  • 20–100 kHz
  • 105 kHz
Type of field: electric and magnetic

Measurements (acc. to literature)

electric field strength 0.111 mV/m (maximum, simulated) operating frequency: 35kHz maximum given for the whole body of the pregnant woman (including fetus) [1]
0.037 V/m (maximum, simulated) operating frequency: 105 kHz in the body of a pregnant 50 kg woman in the 26 th week of gestation [1]
0.093 V/m (maximum) operating frequency: 35 kHz maximum simulated value in the body of a 6-year-old boy weighing 19 kg [1]
0.111 V/m (maximum, simulated) operating frequency: 35 kHz in the body of a pregnant 50 kg woman in the 26 th week of gestation [1]
0.218 V/m (maximum, simulated) operating frequency: 105 kHz in the body of a pregnant 90 kg woman in the 30 th week of gestation [1]
0.281 V/m (maximum, simulated) operating frequency: 35 kHz in the body of a 6-year-old boy weighing 19 kg [1]
0.66 V/m (maximum, simulated) operating frequency: 35kHz in the body of a pregnant 90 kg woman in the 30 th week of gestation [1]
0.752 V/m (maximum, simulated) operating frequency: 105 kHz in the body of an 11-year-old girl weighing 36 kg [1]
2.28 V/m (maximum, simulated) operating frequency: 35 kHz in the body of an 11-year-old girl weighing 36 kg [1]
4.3–4.9 V/m (measured) operating frequencies: 22 - 34 kHz at a distance of 30 cm [2]
10 V/m (maximum) operating frequencies: 20-60 kHz at a distance of 10 cm [3]
220 V/m (maximum, measured) measurement bandwidth: 5 Hz - 32 kHz in the middle of the hob with four pots being heated during the measurement [4]
current density 4 mA/m² (maximum, measured) operating frequency: 20kHz at a distance of 30 cm [5]
5.2 mA/m² (maximum, measured) operating frequency: 105 kHz in the body of an 11-year-old girl weighing 36 kg [1]
8 mA/m² (maximum, measured) operating frequency: 20kHz at a distance of 20 cm [5]
9 mA/m² (maximum, simulated) operating frequency: 105 kHz in the body of a pregnant 90 kg woman in the 30 th week of gestation [1]
14 mA/m² (maximum, simulated) operating frequency: 105kHz in the body of a pregnant 90 kg woman in the 30 th week of gestation [1]
15 mA/m² (maximum, simulated) operating frequency: 105 kHz in the body of a pregnant 50 kg woman in the 26 th week of gestation [1]
16 mA/m² (maximum, simulated) operating frequency: 35 kHz in the body of an 11-year-old girl weighing 36 kg [1]
27 mA/m² (maximum, simulated) operating frequency: 35kHz in the body of a 6-year-old boy weighing 19 kg [1]
30 mA/m² (maximum, measured) operating frequency: 20 kHz at a distance of 10 cm [5]
42 mA/m² (maximum, simulated) operating frequency: 35 kHz in the body of a pregnant 90 kg woman in the 30 th week of gestation [1]
46 mA/m² (maximum, simulated) operating frequency: 35 kHz in the body of a pregnant 50 kg woman in the 26th week of gestation [1]
90 mA/m² (maximum, measured) operating frequency: 20 kHz at the device end [5]
magnetic field strength 0.7–1.6 A/m (measured) operating frequencies: 22 - 34 kHz at a distance of 30 cm [2]
0.7–1.6 A/m (measured) operating frequencies: 26 - 29 kHz at a distance of 30 cm [2]
magnetic flux density 0.7 µT (measured) operating frequency: 20.3 kHz at a distance of 235 mm; power: 1 coil with 2.5 kW [6]
2–6 µT (maximum) operating frequencies: 15 - 25 kHz at a distance of 20 cm [7]
2 µT (maximum, measured) operating frequencies: 15 - 25 kHz at a distance of 50 cm [7]
2.596 µT (measured) - at a distance of 25 cm for a not-centrally positioned pot; measurement performed from the left side; for comparison, the magnetic flux density of a centrally positioned pot is only 0.25 µT [8]
2.7 µT operating frequency: 22.5 kHz at a distance of 170 mm; power: 1 coil with 6 kW [6]
3.02 µT (measured) - at a distance of 0 cm for a not-centrally positioned coffee pot; measurement performed from the front side; for comparison, the magnetic flux density of a centrally positioned pot is even 14.9 µT [8]
3.75 µT (measured) - at a distance of 0 cm for a not-centrally positioned coffee pot; measurement performed from the left side; for comparison, the magnetic flux density of a centrally positioned pot is even 20.8 µT [8]
4–25 µT (maximum) operating frequencies: 15 -25 kHz on the saucepan's base [7]
5 µT (maximum, measured) operating frequency: 20 kHz at a distance of 20 cm; position of the pot: exactly over the induction area [9]
5.15 µT (measured) - at a distance of 0 cm for a not-centrally positioned pot; measurement performed from the left side; for comparison, the magnetic flux density of a centrally positioned pot is only 0.47 µT [8]
5.264 µT (measured) - at a distance of 25 cm for a not-centrally positioned pot; measurement performed from the front side; for comparison, the magnetic flux density of a centrally positioned pot is only 0.346 µT [8]
6.1 µT (measured) operating frequency: 20.3 kHz at a distance of 190 mm; power: 1 coil with 5 kW [6]
6.4 µT (measured) - at a distance of 0 cm for a not-centrally positioned coffee pot; measurement performed from the back side; for comparison, the magnetic flux density of a centrally positioned pot is even 28 µT [8]
6.7 µT (measured) operating frequency: 19.5 kHz at a distance of 260 mm, power: 1 coil with 5 kW [6]
6.75 µT (maximum, simulated) operating frequency: 20 kHz at a distance of 30 cm [5]
7.695 µT (measured) - at a distance of 0 cm for a not-centrally positioned pot; measurement performed from the back side; for comparison, the magnetic flux density of a centrally positioned pot is only 0.42 µT [8]
8.2 µT (measured) operating frequency: 19.5 kHz at a distance of 190 mm; power: 1 coil with 7 kW [6]
9.3–47 µT (maximum, measured) opearting frequency: 20 kHz, mb: 30 Hz - 400 kHz front left cooking plate is heating, measurement position in front of the front right plate [10]
9.5–61 µT (measured) operating frequency: 20 kHz, mbw: 30 Hz - 400 kHz front right cooking plate is heating, measurement position in front of the heating plate [10]
10.494 µT (measured) - at a distance of 0 cm for a not-centrally positioned coffee pot; measurement performed from the right side; for comparison, the magnetic flux density of a centrally positioned pot is even 41.18 µT [8]
11.217 µT (measured) - at a distance of 0 cm for a not-centrally positioned pot; measurement performed from the right side; for comparison, the magnetic flux density of a centrally positioned pot is only 0.767 µT [8]
13.6 µT (measured) - at a distance of 0 cm for a not-centrally positioned pot; measurement performed from the front side; for comparison, the magnetic flux density of a centrally positioned pot is only 1.536 µT [8]
19.4 µT (measured) operating frequency: 22.5 kHz at a distance of 210 mm; power: 4 coils with 9 kW in total [6]
20 µT (maximum, measured) opearting frequency: 20 kHz at a distance of 30 cm [5]
21.8 µT (measured) operating frequency: 22.5 kHz at a distance of 170 mm; power: 4 coils with 9 kW in total [6]
22.4 µT (measured) operating frequency: 21.8 kHz at a distance of 210 mm; power: 2 coils with each 3.5 kW [6]
22.9 µT (measured) operating frequency: 21.8 kHz at a distance of 170 mm; power: 4 coils with 9 kW in total [6]
23.2 µT (measured) opearting frequency: 19.5 kHz at a distance of 180 mm; power: 2 coils with each 3.5 kW [6]
27.4 µT (measured) operating frequency: 19.5 kHz at a distance of 160 mm, power: 2 coils with each 3.5 kW [6]
29.9 µT (measured) - at a distance of 0 cm for a not-centrally positioned pot; measurement performed from the back side; for comparison, the magnetic flux density of a centrally positioned pot is only 4.2 µT [8]
40 µT (maximum) operating frequency: 20 kHz at a distance of 20 cm slightly sloping to the pot at heating level 5 (out of 9); position of the pot: eccentrically over the induction area [9]
47.8 µT (measured) - at a distance of 0 cm for a not-centrally positioned pot; measurement performed from the right side; for comparison, the magnetic flux density of a centrally positioned pot is only 7.46 µT [8]
52.9 µT (measured) operating frequency: 19.5 kHz at a distance of 260 mm, power: 2 coils with each 3.5 kW [6]
55–84 µT (measured) operating frequency: 20 kHz, mbw: 30 Hz - 400 kHz cooking plate consists of only 1 plate, measurement in the middle of this plate [10]
60 µT (maximum, measured) operating frequency: 20 kHz at the device edge [5]
72 µT (maximum) operating frequency: 20kHz at a distance of 20 cm over the pot at heating level 5 (out of 9); position of the pot: eccentrically over the induction area [9]
300 µT (maximum, simulated) operating frequency: 20 kHz at the device edge [5]
4,000–9,000 µT (maximum) measurement bandwidth: 5 Hz + 2 kHz - [11]
8.032 mT (maximum, calculated) - at the surface of the device at 50 Hz [12]
0.07 T (maximum) measurement bandwidth: 50 Hz - 10 kHz - [13]

References

  1. Kos B et al. (2011): Pre- and post-natal exposure of children to EMF generated by domestic induction cookers.
  2. Mantiply ED et al. (1997): Summary of measured radiofrequency electric and magnetic fields (10 kHz to 30 GHz) in the general and work environment.
  3. Swerdlow AJ et al. (2012): Health Effects from Radiofrequency Electromagnetic Fields - RCE 20.
  4. Leitgeb N et al. (2008): Electric emissions from electrical appliances.
  5. Christ A et al. (2012): Exposure of the human body to professional and domestic induction cooktops compared to the basic restrictions.
  6. Guldimann R et al. (2011): [Magnetic field exposure from professional induction hotplates - Health protection for occupational exposure. Measurements at workplaces in the gastronomy in the year 2009/2010].
  7. Rickli H et al. (2003): Induction ovens and electromagnetic interference: what is the risk for patients with implanted pacemakers?
  8. Bullo M et al. (2013): Analysis of Stray EM Fields Generated by Induction Cooktops.
  9. Binggeli C et al. (2005): Induction ovens and electromagnetic interference: what is the risk for patients with implantable cardioverter defibrillators?
  10. Viellard C et al. (2007): B-Field Exposure From Induction Cooking Appliances. ITIS-Foundation
  11. Leitgeb N et al. (2008): Magnetic emissions of electric appliances.
  12. Leitgeb N et al. (2008): Magnetic emission ranking of electrical appliances. A comprehensive market survey.
  13. Tenforde TS (1992): Biological interactions and potential health effects of extremely-low-frequency magnetic fields from power lines and other common sources.