Lectures of ENVIRONMENTAL ELECTRICAL SCIENCE

Transcription

1 Lectures of ENVIRONMENTAL ELECTRICAL SCIENCE CEI EN Standard Presentation edited by: Prof. Alvise Maschio Department of Industrial Engineering University of Padova 12/9/13 1/11

2 Index of lecture 19 Application of the CEI EN Standard 19.1 Introduction 19.2 Field of application the magnetic fields 12/9/13 2/11

3 19.1 Introduction This standard has been approved by CENELEC February 1 st, The last date before which the standard should be acknowledged at national level (through publication of an identical national standard or adoption) was February 1 st, The national standards contrasting EN had be withdrawn before February 1 st, /9/13 3/11

4 19.2 Field of application - 1 The standard concerns the electromagnetic fields and defines methods for evaluating electric and magnetic fields for frequencies up to 300 GHz around household and similar electrical appliances. In reality the object of the standard is limited to the magnetic fields in the frequency band included between 10 Hz and 400 khz. The microwave ovens are not included, because they are subjected to the standard EN /9/13 4/11

5 19.2 Field of application - 2 A hot spot is defined as a localized area with high magnetic field due to unevenness in the field distribution. A coupling factor is defined as a factor which takes into account the magnetic field unevenness around the appliances and the dimensions of a part of the human body. 12/9/13 5/11

6 the magnetic fields - 1 The magnetic field sensor must be formed by three concentric coils, with a measuring area of 100 cm 2 ± 5 cm 2. The coupling factor may be determined by means of an isotropic sensor with a measuring area of 3 cm 2 ± 0.3 cm 2. An evaluation of the coupling factor as a function of the measure distance is included in the standard. 12/9/13 6/11

7 the magnetic fields - 2 A measurement of the magnetic flux density in the time domain is done, along the three Cartesian axes. The measured values are multiplied by the transfer function shown in the standard. The results are squared, summed and averaged out in the measuring interval; the square root gives the rms value of the magnetic flux density normalized at 50 Hz. 12/9/13 7/11

8 the magnetic fields - 3 The weighed value W is given by the following relationship: W = α c(r 1 ) B rms B RL α c (r 1 ) is the coupling factor and B RL the limit value of the magnetic flux density at 50 Hz; W must be not greater than one. 12/9/13 8/11

9 the magnetic fields - 4 As an alternative the discrete spectrum, if available, can be used (e.g., magnetic fields with fundamental frequency at 50 Hz and some harmonics). In this case the weighed value W is given by: W = α c (r 1 ) n 1 B f B RLf 2 where: B f = 2 B xf 2 + B yf 2 + B zf 12/9/13 9/11

10 the magnetic fields - 5 The standard gives, for every appliance typology, measuring distances, sensor positions, exercise conditions and coupling factors. The standard defines also the criteria to be followed as far as measuring uncertainties are concerned. 12/9/13 10/11

11 the magnetic fields - 6 The appliances are considered fulfilling the base limits if the reference levels are not exceeded, taking also into account the coupling factor. If necessary, the coupling factor can be calculated again according to the criteria of the standard. If the reference value is still exceeded, calculation methods can be used (some of them still preliminary) to verify if the base limit is fulfilled. 12/9/13 11/11