Taking into account the mains voltage, the length of the section considered, the nominal intensity,
start-up intensity and the impedance of the conductor selected, voltage drops can be worked out
for the start-up phase and normal running phase using the following formulas:
Three-phase alternative current:
ΔU = √3 . Z . Lt . I
.
Continuous current:
ΔU = 2 . R . Lt . I
.
Voltage drop in %:
ΔU% = (ΔU/U) x 100
.
I: current in continuous operation or at start-up, as appropriate (in Amperes)
Lt: length of the section considered (in m), taking Lt as per paragraph 4
Z: line impedance (in Ω/m) (see general technical data, paragraph 12 for Elite, 11 for Movit)
R: line resistance (in Ω/m) (see general technical data, paragraph 12 for Elite, 11 for Movit)
U: mains voltage (in Volts)
In the case of impulse running, the voltage drop can be quickly checked using the "continuous
operation" and "start-up" graphs (see on the following pages).
When operating at 60Hz, overheating is similar, but voltage drop is greater:
For any given intensity:
X
60
being the reactance at 60Hz
calculate X
60
=X
50
x 60 then re-calculate impedance at 60Hz
X
50
being the reactance at 50Hz
50
𝑍
60
= √𝑅
2
+ 𝑋
60
2
4.
FEEDING: LENGTH OF LINE SECTIONS
It is possible to have several feeding points along a line.
The judicious positioning of these points means voltage drop can be reduced.
If L is the line length, Lt is the maximum length of the section to be taken into account to work out
the voltage drop:
One end-line feeding point
One midway feeding point
Two feeding points
Mobilis line calculation
Three feeding points
Four feeding points
Five feeding points
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Edité le 04/01/2017
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