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
Compliant to RoHS directive 2002/95/EC
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 millimeter
s
RPS 250D
73
56
10.5
26
± 1
16.5
5.7
57
34
Ø 7.2
35.8
2 M4 USEFUL DEPTH: 6
60
Ø 4.2
Note
• Tolerance unless stated: ± 0.2 mm
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
Tolerance
Power Rating chassis mounted
250 W
1000 W
Temperature Coefficient
Standard
Limiting Element Voltage U
L
0.24
to
1 M E24 series
± 1 % to ± 10 %
at 50 °C continuous
at 25 °C for 10 s
± 250 ppm/°C < 1
± 150 ppm/°C > 1
5 kV
RMS
ENVIRONMENTAL SPECIFICATIONS
Thermal Resistance
Temperature Range
Climatic Category
R
TH (j - c)
0.22 °C/W
- 55 °C + 125 °C
55/125/56
Dielectric Strength
L connections 7 kV
RMS
MIL STD 202 (301), 1 min, 10 mA max.
H connections 12 kV
RMS
Insulation Resistance
Inductance
Capacitance Resistor/
Ground
> 10
6
M
< 50 nH
< 40 pF
< 120 pF
Document Number: 50007
Revision: 13-Jan-11
For technical questions, contact:
sfer@vishay.com
www.vishay.com
55
RPS 250
Vishay Sfernice
Power Resistor for Mounting onto a Heatsink
Thick Film Technology
PERFORMANCE
TESTS
Momentary Overload
Rapid Temperature Change
Load Life
Humidity (Steady State)
CONDITIONS
NF EN 140000 CEI 115_1
4
P
r
/10 s/U
L
= 5000 V
NF EN 140000 CEI 68214 Test Na
5 cycles
- 55 °C + 125 °C
NF EN 140000 CEI 115_1
1000 h
P
r
at 70 °C
MIL STD 202 Method 103 B and D
56 days R.H. 95 %
REQUIREMENTS
< ± (0.25 % + 0.05
)
< ± (0.25 % + 0.05
)
< ± (0.5 % + 0.05
)
< ± (0.5 % + 0.05
)
RESISTANCE VALUE IN RELATION TO TOLERANCE AND TCR
Ohmic Value
Standard Tolerance
Standard TCR (- 55 °C to + 125 °C)
Tolerance On Request
<1
±5%
± 250 ppm/°C
± 1 %/± 2 %/± 10 %
> 1
±5%
± 150 ppm/°C
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 (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 on Heatsink
RPS 250
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.
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:
T
-
P = ----------------------------------------------------------
R
TH (j - c)
+ R
TH (c - a)
P:
T:
R
TH (j - c)
:
R
TH (c - a)
:
Example:
R
TH (c - a)
:
Expressed in W
Difference between maximum working temperature and room temperature
Thermal resistance value measured between resistive layer and outer side of the resistor. It is the thermal
resistance of the component: (see Environmental Specifications ).
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.
for RPS 250 power dissipation 180 W at + 50 °C room temperature.
T 125
°C - 50 °C
75 °C
T
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
For technical questions, contact:
sfer@vishay.com
Document Number: 50007
Revision: 13-Jan-11
www.vishay.com
56
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
U
n
.
U
max.
< 2.5
U
n
< 12 500 V.
Short time overload:
4
P
n
/10 s
Accidental overload:
The values indicated on the graph
below are applicable to resistors in air or mounted onto a
heatsink.
Vishay Sfernice
POWER RATING
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.
ENERGY CURVE
10 000
100
100
RATED POWER IN %
10
-5
10
-4
10
-3
10
-2
10
-1
1
1000
80
ENERGY IN J
60
10
40
1
20
0.13
10
-6
0
0
20
40
60
80
100
120
140
OVERLOAD DURATION IN s
HEATSINK TEMPERATURE IN °C
MARKING
Series, style, ohmic value (in
),
tolerance in %,
manufacturing date, Vishay Sfernice trademark
PACKAGING
Box of 15 units
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
48R7
= 48.7
47R0
= 47
1001
= 1 k
4R70
= 4.7
R240
= 0.24
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
Document Number: 50007
Revision: 13-Jan-11
For technical questions, contact:
sfer@vishay.com
www.vishay.com
57
Legal Disclaimer Notice
Vishay
Disclaimer
ALL PRODUCT, PRODUCT SPECIFICATIONS AND DATA ARE SUBJECT TO CHANGE WITHOUT NOTICE TO IMPROVE
RELIABILITY, FUNCTION OR DESIGN OR OTHERWISE.
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 in any datasheet or in any other
disclosure relating to any product.
Vishay makes no warranty, representation or guarantee regarding the suitability of the products for any particular purpose or
the continuing production of any product. To the maximum extent permitted by applicable law, Vishay disclaims (i) any and all
liability arising out of the application or use of any product, (ii) any and all liability, including without limitation special,
consequential or incidental damages, and (iii) any and all implied warranties, including warranties of fitness for particular
purpose, non-infringement and merchantability.
Statements regarding the suitability of products for certain types of applications are based on Vishay’s knowledge of typical
requirements that are often placed on Vishay products in generic applications. Such statements are not binding statements
about the suitability of products for a particular application. It is the customer’s responsibility to validate that a particular
product with the properties described in the product specification is suitable for use in a particular application. Parameters
provided in datasheets and/or specifications may vary in different applications and performance may vary over time. All
operating parameters, including typical parameters, must be validated for each customer application by the customer’s
technical experts. Product specifications do not expand or otherwise modify Vishay’s terms and conditions of purchase,
including but not limited to the warranty expressed therein.
Except as expressly indicated in writing, Vishay products are not designed for use in medical, life-saving, or life-sustaining
applications or for any other application in which the failure of the Vishay product could result in personal injury or death.
Customers using or selling Vishay products not expressly indicated for use in such applications do so at their own risk and agree
to fully indemnify and hold Vishay and its distributors harmless from and against any and all claims, liabilities, expenses and
damages arising or resulting in connection with such use or sale, including attorneys fees, even if such claim alleges that Vishay
or its distributor was negligent regarding the design or manufacture of the part. Please contact authorized Vishay personnel to
obtain written terms and conditions regarding products designed for such applications.
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. Product names and markings noted herein may be trademarks of their respective owners.
Document Number: 91000
Revision: 11-Mar-11
www.vishay.com
1
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