For the general population, a safety factor of 5 is applied, resulting in an exposure limit of 100 µT at 50 Hz (or 83 µT at 60 Hz).
With regards to occupational exposure, this has been associated with an MFD of 500 µT at 50 Hz (or 420 µT at 60 Hz). A threshold of 10 mA/m 2 of current density was selected since lower values do not reveal health risks for humans. The established limits in these recommendations are based on the measurable phenomenon of induced currents in human organs.
This conclusion led the International Commission on Non-Ionizing Radiation Protection (ICNIRP), an independent organization with a great international prestige, to publish some recommendations on the general public’s exposure to electromagnetic fields, which were adopted by the World Health Organization (WHO). This risk is verified at locations where the average value of B → exceeds the threshold of 0.4 µT. The same authors of the aforementioned report carried out a bibliographic review several years later in which the main conclusion was that there is some evidence of a risk factor with an average value of 2 on this childhood disease that has a low incidence in the whole population. Other researchers have tried to verify this influence with diverse results. A real case study has been described to show how the reconfiguration of conductors in a distribution transformer substation (DTS) allows significant reductions in MFD in some points outside the facility. This allows designers to guarantee that legal limits (occupational, general population, or precautionary levels related to epidemiological studies) are fulfilled. With this software, exposure levels can be studied in any hypothetical scenario, even in inaccessible zones. MFDs calculated by CRMag® have been validated in real facilities and laboratory tests. Users can easily model electrical facilities through a friendly and simple data entry. Using the simplified Maxwell equations for low frequencies, CRMag® calculates and represents the magnetic flux density (MFD) that electrical currents produce in the environment.
#Magnetic flux formula software
For this purpose, CRMag® software has been developed. Hence, it is crucially important that we are able to quantify these fields under the normal operating conditions of the facilities, both in their premises and in their surroundings, in order to take the appropriate corrective measures and assure the safety conditions imposed, in force, by regulations. Next we calculate the magnetizing forces in the centre and outer legs MFc and MFo by lookups in the digitized material property data for steel (see Flux density vs magnetizing force for mild steel material above).The World Health Organization (WHO) warns that the presence of magnetic fields due to the circulation of industrial frequency electrical currents may have repercussions on the health of living beings. Then we use the following formulae to calculate flux density in the centre and outer legs Bc and Bo (Bg is the required flux in the gap, specified by the user). The cross-sectional area of the gap Ag is either taken to be equal to that of the centre leg or is specified by the user, depending on the analysis case. We estimate the current required in the coil to achieve a given flux density in the gap.įirst we calculate the cross-sectional areas of the centre and outer legs Ac and Ao from the specified width and thickness values. This case concerns a 3-leg magnetic circuit with an electrical coil wound around the centre leg.
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