10
Power Supply
Technical Information
●
Wiring in Consideration of Voltage Drop
Make the input and output wiring as thick and short as possible to minimize voltage drop.
Selection of Wires
Select wires for the Power Supply carefully. Refer to this table when selecting the wires.
Recommended Maximum Current: Current The table is applicable to wires with 1 to 4 conductors. Keep the cur-
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.
Voltage Drop per Meter (UL1015 Vinyl-sheathed Wires for Heat-resistant
Equipment)
Note. The current indicates the allowable current. In practice, application must be below the recommended current
values.
AWG No.
Cross-
sectional
area
(mm
2
)
Configura-
tion
(number of
conduc-
tors/mm)
Voltage drop per 1 A
(mV/meter)
Recommended maximum current (A)
UL1007
(300 V 80
°
C)
UL1015
(600 V 105
°
C)
30
0.051
7/0.102
358 0.12
---
28
0.081
7/0.127
222 0.15
0.2
26
0.129
7/0.16
140 0.35
0.5
24
0.205
11/0.16
88.9 0.7
1.0
22
0.326
17/0.16
57.5
1.4
2.0
20
0.517
26/0.16
37.6
2.8
4.0
18
0.823
43/0.16
22.8
4.2
6.0
16
1.309
54/0.18
14.9
5.6
8.0
14
2.081
41/0.26
9.5
---
12.0
12
3.309
65/0.26
6.0
---
22.0
10
5.262
104/0.26
3.8
---
35.0
Load
Power Supply
Voltage drop due to wiring
V
O
I
O
V
L
(1)Select a wire diameter suitable for the load current I
O
.
(2)Make sure that the Power Supply’s output voltage V
O
does not exceed the specified
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).
Voltage drop (mV)
1,000
AWG28
(See note.)
700
500
300
100
70
50
30
10
0.1
0.3
0.5
0.7
1
3
5
7
10
30
50
70 100
Current (A)
AWG26
AWG24
AWG22
AWG20
AWG18
AWG16
AWG14
AWG12
AWG10
●
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.
●
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.
Calorific
value (W)
=
Input power
−
Output power
=
Output power
−
Output power
Efficiency
