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83
-
5
15
-
0
00
Rev.
B
20
CAUTION
When local sensing, a short from
+LS or +S to
-
V or
-
S or
-
LS,
will cause damage to the power supply. Reversing the sense
wires might cause damage to the power supply in local and
remote sensing. (Do not connect
-
S to +V or +S to
-
V).
Maximum length in meters to limit
voltage drop to 1V or less
Cross sect.
area
(mm
²
)
Resistivity
OHM/Km
10A
20A
50A
100A
200A
400A
2.5
8.21
12.0
6.0
2.4
1.2
0.6
0.3
4
5.09
18.6
9.8
4.0
2
1.0
0.5
6
3.39
29.4
14.8
5.8
2.9
1.45
0.7
10
1.95
51.2
25.6
10.2
5.1
2.5
1.25
16
1.24
80.0
40.0
16.0
8
4
2
25
0.795
125.0
62.0
25.2
12.6
6.3
3.1
35
0.565
177.0
88.0
35.4
17.7
8.8
4.4
Table 3
-
3: Maximum wire length for 1 V drop on
lead (in meters)
For currents not shown in Table 3
-
2 and 3
-
3, use the formula:
Maximum length=1000/(current x resistivity)
Where current is expressed in Amperes and resistivity in ohms/km or ohms/1000ft.
3.9.3
Wire termination
The wires should be properly termi
nated with terminals securely attached. DO NOT use unterm
i
nated
wires for load connection at the power supply.
3.9.4
Noise and Impedance Effects
To minimize the noise pickup or radiation, the load wires and remote sense wires should be twisted
pairs to th
e shortest possible length. Shielding of sense leads may be necessary in high noise env
i-
ronments. Where shielding is used, connect the shield to the chassis via a rear panel Ground screw.
Even if noise is not a concern, the load and remote sense wires shou
ld be twisted
-
pairs to reduce
coupling, which might impact the stability of power supply. The sense leads should be separated from
the power leads.
Twisting the load wires reduces the parasitic inductance of the cable, which could produce high fr
e-
quency v
oltage spikes at the load and the output of the power supply, because of current variation in
the load itself.
The impedance introduced between the power supply output and the load could make the ripple and
noise at the load worse than the noise at the pow
er supply rear panel output. Additional filtering with
bypass capacitors at the load term
i
nals may be required to bypass the high frequency load current.
3.9.5
Inductive loads
Inductive loads can produce voltage spikes that may be harmful to the power supply. A diode should
be connected across the output. The diode voltage and current rating shou
ld be greater than the
power supply maximum output voltage and cu
r
rent rating. Connect the cathode to the positive output
and the anode to the negative output of the power supply.
Where positive load transients such as back EMF from a motor may occur, conn
ect a surge suppre
s-
sor across the output to protect the power supply. The breakdown voltage rating of the suppressor
must be approximately 10% higher than the max
i
mum output voltage of the power supply.