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© Siemens AG 2007<br />
CD-K <strong>System</strong> — 25 ... <strong>40</strong> A<br />
Engineering information<br />
Short-circuit protection alone<br />
A system can be protected against short-circuit alone, by fitting<br />
low-voltage LV HRC fuse links (gL) into the incoming supply; the<br />
fuse size to be appropriate for the prospective short-circuit<br />
current at the point of installation.<br />
Voltage drop<br />
Voltage drop at rated current<br />
(Load distribution factor a = 0.5 for lighting systems)<br />
Three-phase current (3 ~), alternating current (~)<br />
<strong>System</strong><br />
CD-K-130.<br />
CD-K-1<strong>40</strong>. (-2<strong>40</strong>.)<br />
CD-K-225.<br />
Protective device per circuit<br />
I cf = 25 kA 1)<br />
NH00 32 gL<br />
NH00 <strong>40</strong> gL<br />
NH00 25 gL<br />
1) I cf = Rated short-circuit current of the busbar trunking system and its outgoing<br />
circuits when protected by fuses<br />
Overcurrent protective devices for overload and short-circuit<br />
protection<br />
Due to their high response threshold (1.3 to 1.6 times rated<br />
current) and their long rupturing times at small overcurrents,<br />
fuses are not suitable for overload protection.<br />
For protecting the CD busbar trunking system and its outgoing<br />
circuits, we recommend miniature circuit-breakers and motorprotective<br />
circuit-breakers.<br />
<strong>System</strong><br />
Protective device per circuit<br />
I cc = 15 kA 1) I cc = 20 kA I cc = 25 kA<br />
CD-K-130. 3SY4 332-6 3SY8 332-7 PKZ 2/ZM-32-8<br />
CD-K-1<strong>40</strong>. (-2<strong>40</strong>.) 3SY4 3<strong>40</strong>-6 3SY8 3<strong>40</strong>-7 PKZ 2/ZM-<strong>40</strong>-8<br />
CD-K-225. 3SY4 325-6 3SY8 325-7 PKZ 2/ZM-25-8<br />
1) I cf = Rated short-circuit current of the busbar trunking system and its outgoing<br />
circuits when protected by circuit-breakers<br />
Temperature characteristic of CD systems<br />
U (V/100 m)<br />
20<br />
18<br />
16<br />
14<br />
12<br />
10<br />
8<br />
6<br />
4<br />
2<br />
30 A (~)<br />
30 A (3~)<br />
<strong>40</strong> A (~)<br />
<strong>40</strong> A (3~)<br />
25 A (~)<br />
25 A (3~)<br />
0,4 0,5 0,6 0,7 0,8 0,9 1,0<br />
cos<br />
NSV0_00033<br />
3<br />
Rated current (%)<br />
130<br />
120<br />
110<br />
100<br />
90<br />
80<br />
70<br />
-5<br />
+5 +15 +25 +35 +45 +55 +65<br />
Ambient temperature °C<br />
(average over 24 h)<br />
NSV0_00034<br />
Calculation of the voltage drop<br />
For long busbar runs, it may be necessary to calculate the<br />
voltage drop.<br />
Alternating current:<br />
∆U = a × I ×2l × (R × cos ϕ + X ×sinϕ) ×10 –3<br />
Three-phase current:<br />
∆U = a × !3 ×I × l ×(R × cos ϕ + X ×sinϕ) ×10 –3<br />
with<br />
∆U = Voltage drop (V)<br />
I = Load current (A)<br />
l = Length (m)<br />
a = Load distribution factor see Table<br />
R = Ohmic resistance R 20 (mΩ/m)<br />
X = Inductive resistance X 20 (mΩ/m)<br />
cos ϕ = Power factor<br />
Factor a used in the equation for calculating the voltage drop is<br />
dependent on the load distribution.<br />
(V)<br />
(V)<br />
Load distribution<br />
A<br />
B<br />
Factor a<br />
Supply at A,<br />
one tap-off at B 1<br />
A<br />
B<br />
C<br />
D<br />
E<br />
Supply at A,<br />
tap-offs at B, C, D, E 0.5<br />
A<br />
C<br />
D<br />
E<br />
F<br />
B<br />
Supply at A, B,<br />
tap-off at C, D, E, F 0.25<br />
Siemens LV 70 · 2006<br />
3/21
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