Legrand Zucchini busbar catalogue 2013...the backbone of modern buildings

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SCP super compact busbar
technical information
86
n Losses based on the installation method
Thermal dispersion, rating and IP protection degree are independent
from the type of installation (edgeways, flat, vertical)
This means that it is possible to install the SCP busbar trunking system
as preferred, without having to consider a possible system downgrade
Edgeways Flat
n Joule effect losses in busbars
Losses due to the Joule effect are essentially caused by the electrical
resistance of the busbar
Lost energy is transformed into heat and contributes to the heating of
the conduit of the environment
The calculation of power loss is useful data for correct sizing of the
building air conditioning system
Three-phase regime losses are :
Pj = 3 • Rt • Ib 2 • L
1000
In single-phase regime :
Pj =
2 • Rt •Ib 2 • L
1000
Where :
Ib = utilisation current (A)
R t = phase resistance for unit of length of the busbar trunking system,
measured at thermal regime (mΩ/m)
L = busbar length (m)
For accurate calculation, losses must be assessed trunk by trunk,
taking into account the transiting currents ; for example, in the case of
the distribution of the loads represented in the table below
Total losses in the busbar trunking system Pt = P1 + P2 + P3
L1
L2
L3
L L L
l1 l3 l2
I1+I2+I3 I2+I3 I3
Length Transiting Losses
current
1st trunk L1 I1+I2+I3 P1 = 3RtL1(I1+I2+I3)2
2nd trunk L2-L1 I2+I3 P2 = 3Rt(L2-L1) (I2+I3)2
3rd trunk L3-L2 I3 P3 = 3Rt(L3-L2) (I3)2