RPS 250
Vishay Sfernice
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
RPS 250D
73
56
10.5
26
± 1
16.5
5.7
57
34
Ø 7.2
35.8
2 M4 USEFUL DEPTH: 8
• Tolerance unless stated: ± 0.2 mm
60
Ø 4.2
MECHANICAL SPECIFICATIONS
Insulated case
Alumina onto
aluminum base
Resistive Element
Cermet
End Connections
Screws M4, (M5 on
request)
Tightening Torque on connections
2 Nm
Weight
170 g ± 10 %
Mechanical Protection
Substrate
Ø 21
ELECTRICAL SPECIFICATIONS
Resistance Range
Tolerances
Power Rating chassis mounted
250 W
1000 W
Temperature Coefficient
Standard
Limiting Element Voltage U
L
0.24
Ω
to 1M E24 series
± 1 % to ± 10 %
at 50 °C continuous
at 25 °C for 10 s
± 250 ppm/°C < 1
± 150 ppm/°C > 1
5 kVRMS
ENVIRONMENTAL SPECIFICATIONS
Thermal Resistance
Temperature Range
Climatic Category
Document Number: 50007
Revision: 24-Nov-08
Dielectric Strength
L connections 7 kVRMS
MIL STD 202 (301), 1 min, 10 mA max.
H connections 12 kVRMS
Insulation Resistance
> 10
6
MΩ
< 50 nH
< 40 pF
< 120 pF
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31
Inductance
Capacitance Resistor/
ground
R
TH
(j-c) 0.22 °C/W
- 55 °C + 125 °C
55/125/56
For technical questions, contact: sfer@vishay.com
RPS 250
Vishay Sfernice
Power Resistors for Mounting onto a Heatsink
Thick Film Technology
PERFORMANCE
TESTS
Momentary Overload
CONDITIONS
NF EN 140 000 CEI 115_1
4 Pr/10 s/U
L
= 5000 V
NF EN 140 000 CEI 68214 Test Na
5 cycles
- 55 °C + 125 °C
NF EN 140 000 CEI 115_1
1000 h Pr at 70 °C
MIL STD 202 Method 103 B and D
56 days R.H. 95 %
REQUIREMENTS
< ± (0.25 % + 0.05
Ω)
< ± (0.25 % + 0.05
Ω)
< ± (0.5 % + 0.05
Ω)
< ± (0.5 % + 0.05
Ω)
Rapid Temperature Change
Load Life
Humidity (steady state)
RESISTANCE VALUE IN RELATION TO TOLERANCE AND TCR
Ohmic Value
Standard Tolerance
Standard TCR (- 55 °C to + 125 °C)
Tolerance On Request
<1
Ω
±5%
± 250 ppm/°C
± 1 % - ± 2 % - ± 10 %
>1
Ω
±5%
± 150 ppm/°C
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:
(
1
)
ΔT
-
P
=
--------------------------------------------------------------------
[
R
TH
(
j
–
c
)
+
R
TH
(
c
–
a
)]
P:
T:
R
TH
:
R
TH
:
Expressed in W
Difference between maximum working temperature and room temperature
(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).
(c-a): Thermal resistance value measured between outer side of the resistor and room temperature. It is the thermal
resistance of the heatsink, depending on the heatsink itself (type, shape) and the quality of the fastening device.
Example:
R
TH
: (c-a) for RPS 250 power dissipation 180 W at + 50 °C room temperature.
ΔT ≤
125 °C - 50 °C
≤
75 °C
ΔT
75
-
R
TH
(j-c) + R
TH
(c-a) =
-------
=
---------
= 0.42 °C/W
P
180
R
TH
(j-c) = 0.22 °C/W
R
TH
(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.
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For technical questions, contact: sfer@vishay.com
Document Number: 50007
Revision: 24-Nov-08
RPS 250
Power Resistor for Mounting onto a Heatsink
Thick Film Technology
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 s
Accidental overload:
The values indicated on the graph below are applicable to resistors in air or mounted onto a heatsink.
Vishay Sfernice
ENERGY CURVE
10 000
1000
ENERGY IN JOULES
100
10
1
0.13
1 µs
10 µs
100 µs
1 ms
10 ms
100 ms
1s
OVERLOAD DURATION IN SECONDS
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.
100
80
% RATED POWER
60
40
20
0
0
20
40
60
80
100
120
140
HEATSINK TEMPERATURE IN DEGREES CELSIUS
MARKING
Series, style, ohmic value (in
Ω),
tolerance in %, manufacturing date, VISHAY trademark
PACKAGING
Packaging box of 15 units
Document Number: 50007
Revision: 24-Nov-08
For technical questions, contact: sfer@vishay.com
www.vishay.com
33
RPS 250
Vishay Sfernice
Power Resistors for Mounting onto a Heatsink
Thick Film Technology
GLOBAL PART NUMBER INFORMATION
R
P
S
0
2
5
0
D
L
2
R
2
0
J
B
Z
A
3
GLOBAL
MODEL
RPS250
STYLE
D
= Diagonal
connections
A
= Straight
connections
DIELECTRIC
H
= Dielectric
strength 12 kV
L
= Dielectric
strength 7 kV
OHMIC VALUE
The first three digits
are significant figures
and the last digit
specifies the number
of zeros to follow.
R designates decimal
point.
2R20
= 2.20
Ω
48R7
= 48.7
Ω
47R0
= 47
Ω
1001
= 1 kΩ
4R70
= 4.7
Ω
R240
= 0.24
Ω
TOLERANCE
F
=1%
G
=2%
J
=5%
K
= 10 %
PACKAGING
B
= Box, 15 pcs
N
= Box, 15 pcs
N/A
(1 to 14 pcs by box)
TYPE
Standard RPS250A
=
Blank
Standard
RPS250D =
ZA3
Special =
Blank
(for RPS250D) or as
applicable =
ZAx
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34
For technical questions, contact: sfer@vishay.com
Document Number: 50007
Revision: 24-Nov-08
Legal Disclaimer Notice
Vishay
Disclaimer
All product specifications and data are subject to change without notice.
Vishay Intertechnology, Inc., its affiliates, agents, and employees, and all persons acting on its or their behalf
(collectively, “Vishay”), disclaim any and all liability for any errors, inaccuracies or incompleteness contained herein
or in any other disclosure relating to any product.
Vishay disclaims any and all liability arising out of the use or application of any product described herein or of any
information provided herein to the maximum extent permitted by law. The product specifications do not expand or
otherwise modify Vishay’s terms and conditions of purchase, including but not limited to the warranty expressed
therein, which apply to these products.
No license, express or implied, by estoppel or otherwise, to any intellectual property rights is granted by this
document or by any conduct of Vishay.
The products shown herein are not designed for use in medical, life-saving, or life-sustaining applications unless
otherwise expressly indicated. Customers using or selling Vishay products not expressly indicated for use in such
applications do so entirely at their own risk and agree to fully indemnify Vishay for any damages arising or resulting
from such use or sale. Please contact authorized Vishay personnel to obtain written terms and conditions regarding
products designed for such applications.
Product names and markings noted herein may be trademarks of their respective owners.
Document Number: 91000
Revision: 18-Jul-08
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1
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