RPS 250
Vishay Sfernice
Document Number: 50007 For technical questions, contact: sfer@vishay.com www.vishay.com
Revision: 08-Jun-06 31
Power Resistor for Mounting onto a Heatsink
Thick Film Technology
FEATURES
•High power rating: 250 W
•High overload capability up to 4 times Nominal
Power (see energy curve)
•Easy mounting
•Low thermal radiation of the case
Developed for specific applications such as railroad electrical traction, this series can bear short overloads as high as fifteen times
the nominal power. Designed to be mounted onto a heatsink, these power resistors exhibit remarkable characteristics.
DIMENSIONS in millimeters
MECHANICAL SPECIFICATIONS
Mechanical Protection Insulated case
Substrate Alumina onto
aluminum base
Resistive Element Cermet
End Connections Screws M4, (M5 on
request)
Tightening Torque on connections 2 Nm
Weight 170 g ± 10 %
ENVIRONMENTAL SPECIFICATIONS
Thermal Resistance RTH (j-c) 0.22 °C/W
Temperature Range - 55 °C + 125 °C
Climatic Category 55/125/56
RoHS
COMPLIANT
• Tolerance unless stated: ± 0.2 mm
73
56
7
.5
57
34
Ø 7.2
Ø 4.2
8.53
2 M4 USEFUL DEPTH: 8
RPS 250D
5
.
0
1
06
12 Ø
26 ± 1
16.5
ELECTRICAL SPECIFICATIONS
Resistance Range
0.24
Ω
to 1M E24 series
Tolerances
± 1 % to ± 10 %
Power Rating chassis mounted
250 W
1000 W
at 50 °C continuous
at 25 °C for 10 seconds
Temperature Coefficient
Standard
± 250 ppm/°C < 1
± 150 ppm/°C > 1
Limiting Element Voltage
5 kVRMS
Dielectric Strength
MIL STD 202 (301), 1 minute, 10 mA Max
L connections 7 kVRMS
H connections 12 kVRMS
Insulation Resistance
> 10
6
M
Ω
Inductance
< 50 nH
Capacitance Resistor/
ground
< 40 pF
< 120 pF
www.vishay.com For technical questions, contact: sfer@vishay.com Document Number: 50007
32 Revision: 08-Jun-06
RPS 250
Vishay Sfernice Power Resistors for Mounting onto a Heatsink
Thick Film Technology
CHOICE OF THE HEATSINK
The user must choose the heatsink 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 ratio:
P: expressed in W
T: difference between maximum working temperature and room temperature.
RTH: (j-c): thermal resistance value measured between resistive layer and outer side of the resistor. It is the thermal
resistance of the component: (see specifications environmental paragraph).
RTH: (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:
RTH: (c-a) for RPS 250 power dissipation 180 W at + 50 °C room temperature.
ΔT ≤ 125 °C - 50 °C ≤ 75 °C
RTH (j-c) + RTH (c-a) = = = 0.42 °C/W
RTH (j-c) = 0.22 °C/W
RTH (c-a) ≤ 0.42 °C/W - 0.22 °C/W ≤ 0.20 °C/W
RECOMMENDATIONS FOR MOUNTING ONTO A HEATSINK
Surfaces in contact must be carefully cleaned. The heatsink must have an acceptable flatness: 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 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 two screws (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).
In any case the hot spot temperature, measured locally on the case must not exceed 125 °C.
Test should be performed by the user.
PERFORMANCE
TESTS CONDITIONS TYPICAL DRIFTS
Momentary Overload NF EN 140 000 CEI 115_1
4 Pr/10 s < ± (0.25 % + 0.05 Ω)
Rapid Temperature Change
NF EN 140 000 CEI 68214 Test Na
5 cycles
- 55 °C + 125 °C
< ± (0.25 % + 0.05 Ω)
Load Life NF EN 140 000 CEI 115_1
1000 h Pr at 70 °C < ± (0.5 % + 0.05 Ω)
Humidity (steady state) MIL STD 202 Method 103 B and D
56 days R.H. 95 % < ± (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 ± 250 ppm/°C ± 150 ppm/°C
Tolerance On Request ± 1 % - ± 2 % - ± 10 %
PΔT
RTH jc–()RTH ca–()+[]
---------------------------------------------------------------------1()
=
ΔT
P
------- 75
180
----------
RPS 250
Power Resistor for Mounting onto a Heatsink
Thick Film Technology Vishay Sfernice
Document Number: 50007 For technical questions, contact: sfer@vishay.com www.vishay.com
Revision: 08-Jun-06 33
OVERLOADS
In any case the applied voltage must be lower than 2.5 Un. U maxi < 2.5 Un < 12 500 V.
Short time overload: 4 Pn/10 seconds
Accidental overload: The values indicated on the graph below are applicable to resistors in air or mounted onto a heatsink.
ENERGY CURVE
POWER RATING CHART
The temperature of the heatsink should be maintained in the limit specified.
To improve the thermal conductivity, surfaces in contact should be coated with a silicone grease.
MARKING
Series, style, ohmic value (in Ω), tolerance in %, manufacturing date, VISHAY trademark
ORDERING INFORMATION
RPS 250 DL 250U 1 % ZA3 B015 e
MODEL STYLE CONNECTIONS
Optional
H: dielectric strength 12 kV
L: dielectric strength 7 kV
RESISTANCE VALUE TOLERANCE
Optional
± 1 %
± 2 %
± 5 %
± 10 %
CUSTOM DESIGN
Options on request
special TCR,
shape, etc.
PACKAGING LEAD
(Pb)-FREE
SAP PART NUMBERING GUIDELINES
RPS 0250 DL 2500 F B ZA3
MODEL STYLE CONNECTIONS OHMIC VALUE TOLERANCE PACKAGING DESIGN
ENERGY IN JOULES
OVERLOAD DURATION IN SECONDS
1 µs
0.13
1
10
100
1000
10 000
10 µs 100 µs 1 ms 1 s10 ms 100 ms
% RATED POWER
0 20 40 60 80 100 120 140
HEATSINK TEMPERATURE IN DEGREES CELSIUS
0
20
40
60
80
100
Packaging Box of 15 units
Document Number: 91000 www.vishay.com
Revision: 18-Jul-08 1
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Vishay
All product specifications and data are subject to change without notice.
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or in any other disclosure relating to any product.
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therein, which apply to these products.
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