RCH
Vishay Sfernice
Power Resistors, for Mounting onto a Heatsink
Thick Film Technology
FEATURES
•
5 W to 50 W
•
High power rating
•
High overload capabilities up to 2500 V
RMS
•
Wide resistance range from 0R24 to 1 MΩ
Manufactured in cermet thick film technology, these power
resistors exhibit remarkable characteristics and the series
includes 4 types ranging from 5 W to 50 W.
Designed to be mounted onto a heatsink, the resistors can
bear high short time overloads and 3 types of terminations
are available.
The resistors are non inductive and are particularly suitable
for high frequency operation and cut-out circuits.
•
High thermal capacity up to 0.8 °C/W
•
Easy mounting
•
Reduced size and weight
•
High insulation: 10
6
MΩ
DIMENSIONS
in millimeters
RCH...R
Ø2
6
RCH...V
M2
6
RCH...S
H
W
6
3
Ø 2.1
S
L
F
P
4.8
6
ØD
General tolerance: ± 0.3 mm
T
9
DIMENSIONS
MODEL
L
W
H
P Leads Pitch
F Connections Pitch
T
S
ØD
V Leads
Weight (g)
RCH 5
16.6
9
16.4
10.2
11.3
12.5
5.3
2.4
M2
4
RCH 10
19
11
20.6
12.7
14.3
15.9
5
2.4
M2
5
RCH 25
28
14
27.5
18.3
18.3
19.8
7.7
3.2
M3
7
RCH 50
47.8
15.5
29.4
30.5
39.7
21.4
8
3.2
M3
12
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For technical questions, contact: sfer@vishay.com
Document Number: 50006
Revision: 09-Jun-08
Power Resistors, for Mounting onto a Heatsink
Thick Film Technology
MECHANICAL SPECIFICATIONS
Mechanical Protection
Substrate
Resistive Element
Connections
Insulated case
Alumina
Cermet
Tinned copper alloy
RCH
Vishay Sfernice
ELECTRICAL SPECIFICATIONS
Resistance Range
Standard Resistance Tolerances
Power Rating:
Chassis Mounted
Unmounted
5 W to 50 W
2 W to 5.5 W
± 150 ppm/°C (R > 1
Ω)
10
6
MΩ
≤
0.1 µH
0.24
Ω
to 1 MΩ E24 series
± 1 %, ± 2 %, ± 5 %, ± 10 %
ENVIRONMENTAL SPECIFICATIONS
Temperature Range
Climatic Category
- 55 °C to + 125 °C
55/125/56
Temperature Coeffi cient
Insulation Resistance
Total Inductance
PERFORMANCE
TESTS
Momentary Overload
CONDITIONS
NF EN 140 000 CEI 115_1
2
P
r
/5 s
U
s
< 2 UL
NF EN 140 000 125 °C CEI 68215 Test Na
5 cycles
- 55 °C to + 125 °C
NF EN 140 000 CEI 115_1
1000 h
P
r
at + 25 °C
56 days RH 95 %
MIL STD 202 Method 103 B and C
TYPICAL DRIFTS
< ± (0.25 % + 0.05
Ω)
Rapid Temperature Change
< ± (0.25 % + 0.05
Ω)
Load Life
Humidity (Steady State)
< ± (0.5 % + 0.05
Ω)
< ± (0.5 % + 0.05
Ω)
RESISTANCE VALUE IN RELATION TO TOLERANCE AND TCR
Resistance Value
Standard
Tolerances
Standard TCR
Tolerance on Request
± 250 ppm/°C
± 1 % to ± 2 %
<1
Ω
±5%
± 10 %
± 150 ppm/°C
>1
Ω
SPECIAL FEATURES
MODEL
Power Rating-Chassis Mounted
Power Rating-Unmounted
Thermal Resistance R
TH
(j-c)
Limiting Element Voltage (V
RMS
)
Max. Overload Voltage (V
RMS
)
Dielectric Strength (V
RMS
) 50 Hz, 1 Min
MIL STD 202 Method 301 10 mA Max.
Critical Resistance
RCH 5
5W
2W
4.8 °C/W
160 V
320 V
2000 V
5120
Ω
RCH 10
10 W
2.5 W
3.2 °C/W
250 V
500 V
2000 V
6250
Ω
RCH 25
25 W
4W
1.4 °C/W
550 V
1100 V
3500 V
12 100
Ω
RCH 50
50 W
5.5 W
0.8 °C/W
1285 V
2500 V
3500 V
33 024
Ω
Document Number: 50006
Revision: 09-Jun-08
For technical questions, contact: sfer@vishay.com
www.vishay.com
2
RCH
Vishay Sfernice
Power Resistors, for Mounting onto a Heatsink
Thick Film Technology
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,
heat-sink) are coated with a silicone grease (type Sl 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 (not supplied).
Tightening Torque
on heatsink
RCH 5
0.5 Nm
RCH 10
0.6 Nm
RCH 25
0.7 Nm
RCH 50
1 Nm
In order to improve the dissipation, either forced-air cooling or liquid cooling may be used.
A low thermal radiation of the case allows several resistors to be mounted onto the same heatsink.
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.
Tests should be performed by the user.
CHOICE OF THE HEATSINK
The user must choose the heatsink according to 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 resistance layer and outer side of the resistor.
It is the thermal resistance of the component (See Special Features table).
(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 RCH 25 power rating 20 W at ambient temperature + 50 °C.
ΔT ≤
125 °C - 50 °C
≤
75 °C
ΔT
75
R
TH
(j-c) + R
TH
(c-a) =
-------
=
------
= 3.75 °C/W
R
TH
(j-c) = 1.4 °C/W (Special Features)
P
20
R
TH
(c-a)
≤
3.75 °C/W - 1.4 °C/W
≤
2.35 °C/W
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For technical questions, contact: sfer@vishay.com
Document Number: 50006
Revision: 09-Jun-08
Power Resistors, for Mounting onto a Heatsink
Thick Film Technology
OVERLOADS
RCH
Vishay Sfernice
The applied voltage must always be lower than the maximum overload voltage as shown in the special features table.
The values indicated on the graph below are applicable to resistors in air or mounted onto a heatsink.
ENERGY CURVE
1000
100
ENERGY IN JOULES
10
RCH 50
RCH 25
RCH 10
RCH 5
1
0.1
10
- 6
10
- 5
10
- 4
10
- 3
10
- 2
10
- 1
OVERLOAD DURATION IN s
POWER RATING CHART
For resistors mounted onto heatsink and thermal resistance of 1 °C/W.
To improve the thermal conductivity, surfaces in contact should be coated with a silicone grease.
100
H
RC
RC
75
%
RATED POWER
RC
R
H
C
25
H
H5
10
50
50
25
0
0
20
40
60
80
100
120
140
AMBIENT TEMPERATURE IN °C
MARKING
Model, Style, Resistance Value (in
Ω),
Tolerance (in %), Manufacturing Date, VISHAY trade mark.
ORDERING INFORMATION
RCH
MODEL
25
STYLE
3.3 kΩ
RESISTANCE VALUE
±5%
TOLERANCE
Optional
±1%
±2%
±5%
± 10 %
R
CONNECTIONS
Optional
S: Flat with hole
R: Round lead
V: M2 screw
XXX
CUSTOM DESIGN
Optional
Document Number: 50006
Revision: 09-Jun-08
For technical questions, contact: sfer@vishay.com
www.vishay.com
4
RCH
Vishay Sfernice
Power Resistors, for Mounting onto a Heatsink
Thick Film Technology
GLOBAL PART NUMBER INFORMATION
R
C
H
1
0
S
3
3
0
0
0
J
S
0
6
GLOBAL
MODEL
RCH
SIZE
05
10
25
50
LEADS
R
= Round lead
V
= M2 screw
S
= Flat with hole
OHMIC VALUE
The firts four digits are
significant figures and the
last digit specifies the
number of zeros to follow.
R designates decimal point.
4R700
= 4.7
Ω
48701
= 48 700
Ω
33000
= 33 000
Ω
R0100
= 0.01
Ω
R6800
= 0.68
Ω
27000
= 2700
Ω
= 2K7
Ω
TOLERANCE
F
=1%
G
=2%
J
=5%
K
= 10 %
PACKAGING
S06
= Bag
25 pieces
SPECIAL
As applicable
Ex =
XXX
www.vishay.com
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For technical questions, contact: sfer@vishay.com
Document Number: 50006
Revision: 09-Jun-08
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