91 / 132
91
All dimensions (mm) are nominal
One-dimensional trend of the magnetic induction near the junction.
The blue dash shows the ‘objective’ level and the red dash shows
the ‘quality objective’ required by law
n
Measurement of magnetic induction
Since 1994, with a study carried out by Chalmers University of
Technology of Goteborg, Legrand has taken an interest in the issues
linked with the electromagnetic emissions in their Zucchini products,
keeping at the forefront of the latest legislative directive, which has only
recently imposed the quality standards that were already widely met by
Zucchini busbar trunking systems
The ACAE (Association for the Certification of Electric and Electronic
Equipment) certified internal laboratory is capable of carrying out the
measurement of the electromagnetic emissions of busbar trunking
systems. This measurement is nowadays one of the tests to which the
products are subjected before they reach the market
The busbar trunking system in itself already minimises electromagnetic
emissions, which are much lower when compared with those generated
by cables with the same current intensity
It is a well-known fact that the electromagnetic field is the result of the
superimposition of two fields : the electric and the magnetic field
The first is totally shielded by the equipotential metal casing of the
busbar trunking system, while the second is very low due to the
intrinsic characteristic of the busbar trunking system. More precisely,
due to the fact that busbar conductors are extremely close inside
the busbar package, the three busbar conductors, crossed by three
balanced currents displaced by 120°, induce fields that tend to overlap,
cancelling one another, therefore resulting in an extremely low external
impact
However, also in conditions of imperfect current balance, the metal
casing of the busbar trunking system is capable of reducing most of the
magnetic field, which otherwise would spread through the surrounding
environment
The laboratory tests carried out show how the magnetic induction
emitted by SCP busbar trunking systems, measured at a distance of
approximately one metre, is well below the critical value of 3 μT
With Legislative Decree DPCM dated 8/7/2003, Italian law set the first
exposure limit at 100 μT
In addition, in locations where attendance is expected for no less than
four hours a day, an attention value of 10 μT has been set, to avoid
possible long term effects on health
In the decree, the 3 μT threshold is indicated as the ‘quality objective’.
However, as the product is intended for the European and world
market, low magnetic emission is a fundamental point that cannot be
disregarded, to ensure a presence in foreign countries : one example
of this is Germany, where for over 10 years the regulation has set a
cautionary limit of 3 μT as the maximum permitted threshold in certain
structures, for example hospitals, so much so that in these types of
environments the busbar trunking system has become a mandatory
choice, as well as a high quality one
Testing at Legrand’s laboratory in Italy for the approval
certification of Zucchini SCP busbar trunking systems
n
Measurement of magnetic induction (continued)
The high quality standard guaranteed by busbar trunking systems can
be further appreciated by comparing the emission values measured
against those of other commonly used equipment, as taken from table
7·1 of CEI 211-6 standard
The measurements obtained on aluminium SCP busbar trunking
systems with ratings of 2500 A (carried out in compliance with the
requirements of the technical product standard CEI EN 60439-2), show
that the magnetic induction generated by the busbar is in the range of
1·5 - 2 μT at a distance of one metre from the busbar itself
These values also apply near the junction, which is considered the
critical point due to the wider distance between the busbar conductors
in this position
Levels of exposure to industrial frequency magnetic field sources
(table 7.1 from CEI 211-6 standard)
Magnetic
Source
induction
Distance
(µT)
Electric shaver
150-240
on the face
Hairdryer
1-13
10-20 cm
Blender
0·9
40 cm
12 V, 20 W halogen lamp
0·5
30 cm
Aerosol therapy equipment
20-50
20-30 cm
Electric blanket
2
on contact
21 inch television set
0·3
50 cm
Washing machine
3·4
50 cm
Dishwasher
0·05
50 cm
Electric oven
0·4
20 cm
600 W drill
2
on the chest
100 W welding machine
14·5
on the chest
225 W grinder
0·8
40 cm
1100 W compressor
8·2
40 cm
2150 W arc welding machine
23·2
40 cm
75 MW, 55-65 kA, 150 t arc oven
100-270
in proximity
Electric scalpel
2·9
in proximity
Battery charger
22·9
in proximity
Echograph
0·8
operator position
Projector
2·3
20 cm
B (μ T)
Objective level
Quality objective level
25
20
15
10
5
0
20 40 60
80 100 120
CM