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● Extending the Operating Life
• The life of a Power Supply is
determined by the life of the
electrolytical capacitors used inside.
Here, Arrhenius' Law applies, i.e., the
life will be halved for each rise of 10° C
and will be doubled for each drop of
10° C. As a result, the life of the Power
Supply can be increased by reducing
its internal temperature.
• Internal Temperature Reduction
The temperature inside a Power
Supply will remain constant when the
heat generation is equal to the heat
dissipated. The internal temperature
will rise if not enough heat is
dissipated, i.e., the Power Supply
must be mounted to allow proper heat
dissipation.
Due consideration must be given so
that the operating ambient
temperature of the Power Supply falls
within the range specified by the
derating curves.
Heat Dissipation with Natural Air Cooling
• Provide air holes and an ambient
atmosphere that allows air convection
• Use a metal plate as the mounting
panel.
• It is recommended that forced cooling
be used as much as possible.
• The calorific (heating) value of the
Power Supply can be expressed in the
following equation.
Calorific
− Output power
=
Input power
value (W)
Output power
− Output power
=
Efficiency
● Maintenance
Slits are provided in the Power Supply
case to allow heat generated internally
to dissipate externally. It is thus possible
for foreign matter and dirt to enter the
Power Supply and reduce or interrupt
the output. When performing periodic
maintenance, always vacuum away any
foreign matter and dirt from inside the
Power Supply.
10
Power Supply
● Wiring in Consideration of Voltage Drop
Make the input and output wiring as thick and short as possible to minimize voltage drop.
(1)Select a wire diameter suitable for the load current I
(2)Make sure that the Power Supply's output voltage V
output fluctuation range.
(3)Consider the allowable current for load short-circuits (guideline: 1.6 times the Power
Supply's rated output current or higher).
Selection of Wires
Select wires for the Power Supply carefully. Refer to this table when selecting the wires.
Cross-
sectional
AWG No.
area
(mm
30
0.051
28
0.081
26
0.129
24
0.205
22
0.326
20
0.517
18
0.823
16
1.309
14
2.081
12
3.309
10
5.262
Recommended Maximum Current: Current The table is applicable to wires with 1 to 4 conductors. Keep the cur-
Voltage Drop per Meter (UL1015 Vinyl-sheathed Wires for Heat-resistant
Equipment)
1,000
700
500
300
100
70
50
30
10
0.1
Note. The current indicates the allowable current. In practice, application must be below the recommended current
values.
Technical Information
Power Supply
Voltage drop due to wiring
Configura-
tion
Voltage drop per 1 A
(number of
(mV/meter)
conduc-
2
)
tors/mm)
7/0.102
358
7/0.127
222
7/0.16
140
11/0.16
88.9
17/0.16
57.5
26/0.16
37.6
43/0.16
22.8
54/0.18
14.9
41/0.26
9.5
65/0.26
6.0
104/0.26
3.8
rent value to within 80% of the values shown in this table when using wires
having 5 or more conductors. The following chart shows the voltage drop per
meter in terms of the relationship between the current and conductor diame-
ter. Make sure that the current value does not exceed the recommended
maximum current value.
0.3
0.5
0.7
1
I
O
V
V
Load
O
L
.
O
does not exceed the specified
O
Recommended maximum current (A)
UL1007
(300 V 80° C)
0.12
0.15
0.35
0.7
1.4
2.8
4.2
5.6
---
---
---
AWG28
AWG26
AWG24
AWG22
AWG20
AWG18
AWG16
3
5
7
10
30
UL1015
(600 V 105° C)
---
0.2
0.5
1.0
2.0
4.0
6.0
8.0
12.0
22.0
35.0
AWG14
AWG12
AWG10
(See note.)
50
70 100
Current (A)
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