Rph 100, Vishay sfernice – C&H Technology RPH100 User Manual
Page 3
Document Number: 50046
For technical questions, contact: [email protected]
www.vishay.com
Revision: 10-Oct-08
2
RPH 100
Power Resistor for Mounting onto a Heatsink
Thick Film Technology
Vishay Sfernice
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 125 °C. The dissipated power is simply calculated by the following ratios:
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: 0.55 °C/W.
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 RPH 100 power rating 80 W at ambient temperature + 40 °C.
Thermal resistance R
TH
(j-c): 0.55 °C/W
Considering equation (1) we have:
ΔT ≤ 125 °C - 40 °C ≤ 85 °C
R
TH
(j-c) + R
TH
(c-a) =
=
= 1.06 °C/W
R
TH
(c-a)
≤ 1.06 °C/W - 0.55 °C/W ≤ 0.51 °C/W
RECOMMENDATIONS FOR MOUNTING ONTO A HEATSINK
Surfaces in contact must be carefully cleaned.
The heatsink must have an acceptable fl atness: from 0.05 mm to 0.1 mm/100 mm.
Roughness of the heatsink must be around 6.3 µm.
In order to improve thermal conductivity, surfaces in contact (alumina, heatsink) should be coated with a silicone grease (type
SI 340 from Rhône-Poulenc or Dow 340 from Dow Corning).
The fastening of the resistor to the heatsink is under pressure control of four screws (not supplied).
Tightening torque: 3 Nm
In order to improve the dissipation, either forced-air cooling or liquid cooling may be used.
Do not forget to respect an insulation value between two resistors (dielectric strength in dry air 1 kV/mm).
PERFORMANCE
TESTS
CONDITIONS
REQUIREMENTS
Short Time Overload
NF EN 140000 CEI 115_1
4
P
n
/5 s
U
S
< 2
U
L
< ± (0.25 % + 0.05
Ω)
Rapid Temperature Change
NF EN 140000 CEI 68214 Test Na
5 cycles - 55 °C + 125 °C
< ± (0.25 % + 0.05
Ω)
Load Life (Chassis Mounted 0.45 °C/W)
NF EN 140000
P
n
at 25 °C 1000 h
< ± (0.5 % + 0.05
Ω)
Humidity (Steady State)
MIL STD 202 Method 103 B Test D
56 days 95 % RH
< ± (0.5 % + 0.05
Ω)
RESISTANCE VALUE IN RELATION TO TOLERANCE AND TCR
Ohmic Value
< 1
Ω
> 1
Ω
Standard Tolerance
± 5 %
± 5 %
Standard TCR
± 300 ppm/°C
± 150 ppm/°C
Tolerance On Request
± 1 % - ± 2 %
P
ΔT
R
TH
j
c
–
(
) R
TH
c
a
–
(
)
+
[
]
------------------------------------------------------------------
=
1
( )
ΔT
P
-------
85
80
------