Rto 50, Vishay sfernice, Power resistor, thick film technology – C&H Technology RTO50 User Manual
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Document Number: 50035
2
Revision: 24-Nov-08
RTO 50
Vishay Sfernice
Power Resistor, Thick Film Technology
CHOICE OF THE HEATSINK
The user must choose according to the working conditions of the component (power, room temperature).
Maximum working temperature must not exceed 155 °C. The dissipated power is simply calculated by the following ratio:
P:
Expressed in W
T:
Difference between maximum working temperature and room temperature
R
TH (j - c)
:
Thermal resistance value measured between resistive layer and outer side of the resistor. It is the thermal
resistance of the component: (Special Features Table)
R
TH (c - a)
:
Thermal resistance value measured between outer side of the resistor and room temperature. It is the
thermal resistance of the heatsink itself (type, shape) and the quality of the fastening device
Example:
R
TH (c - a)
: For RTO 50 power rating 13 W at ambient temperature + 30 °C
Thermal resistance R
TH (j - c)
: 26 °C/W
Considering equation (1) we have:
ΔT ≤ 155 °C - 30 °C ≤ 125 °C
R
TH (j - c)
+ R
TH (c - a)
=
=
= 9.6 °C/W
R
TH (c - a)
≤ 9 .6 °C/W - 2.6 °C/W ≤ 7 °C/W
PERFORMANCE
TESTS
CONDITIONS
REQUIREMENTS
Momentary Overload
EN 60115-1
2 Pr 5 s for R < 2
Ω
1.6 Pr 5 s for R
≥ 2 Ω
U
S
< 1.5 U
L
± (0.25 % + 0.05
Ω)
Rapid Temperature Change
EN 60115-1
60 068-2-14
5 cycles - 55 °C to + 155 °C
± (0.5 % + 0.05
Ω)
Load Life
EN 60115-1
Pr at + 25 °C, 1000 h CEI 115_1
± (1 % + 0.05
Ω)
Humidity (Steady State)
EN 60115-1
56 days RH 95 %
± (0.5 % + 0.05
Ω)
Vibration
MIL STD 202
Method 204 C Test D
± (0.2 % + 0.05
Ω)
Terminal Strength
MIL STD 202
Method 211 Test A1
± (0.2 % + 0.05
Ω)
SPECIAL FEATURES
Resistance Values
≥ 0.01 Ω
≥ 0.015 Ω
≥ 0.1 Ω
≥ 0.5 Ω
Tolerances
± 1 % at ± 10 %
Temperature
Coefficient
(- 55 °C to + 155 °C)
Standard
± 900 ppm/°C
± 700 ppm/°C
± 250 ppm/°C
± 150 ppm/°C
P
ΔT
R
TH (j - c)
R
TH (c - a)
+
[
]
---------------------------------------------------------- 1
( )
=
ΔT
P
-------
125
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