CFH350A56RJ 데이터 시트보기 (PDF) - TE Connectivity
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CFH350A56RJ Datasheet PDF : 4 Pages
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10 cm
80
Aluminium Housed Power Resistors
Type CFH Series
Application Notes
Power rating. The dissipation power of a resistor depends also from the mounting position. If the resistor
is mounted onto a surface, the latter takes part positively (if it is large and conductive) or
negatively (if it is small and insulating) to the thermal dissipation.
Data of power rating are referred to a resistor mounted vertically, with terminals in the lower side and
away from the nearest surface at least 10cm, in order to avoid thermal influence from the wall.
Surface temperature rise @ Pn. During the load application, the surface temperature is not
homogeneous, and it is higher on the flat surface of the resistor (surface that in the practical application
shall be fixed to a heat sink or to a metallic surface to help the thermal dissipation).
Max.power rating of a resistor mounted onto a heat sink. Standard heat sink is a common heat sink
(as shown) used for the cooling of semiconductors, with two grooves for components mounting.
The distance between the axes of these two grooves is 80 mm. In this case both heat sink and resistor
will be mounted upright. The length of the heat sink shall be at least 40 mm longer than the resistor’s
body (20 mm for each side).
Power rating of a resistor mounted on a water-cooled heat sink. If the heat sink is water-cooled,
power dissipation increases considerably, and the limiting power rating is due to temperature of the
resistor body. In the case illustrated in the specifications board, the temperature of the heat sink is 40°C
and the resistor’s surface reaches 300°C. In this case too, the length of the heat sink shall be at least
20 mm longer than the resistor’s body.
135
Absorbed energy @ 250°C ΔT. It represents the quantity of energy stored into the resistor when it
has reached 250°C of temperature rise. The above indication is an index of the thermal capacity of
the resistor.
Absorbed energy in 5”. It gives an index of behaviour of the resistor to short overloads.
Absorbed energy in time ≥0.2”. During a short impulse (from 0 to 2 sec.), the resistor may stand only
the energy that the thermal capacity of the resistance wire is able to absorb. In fact the phenomenon is
too short to let significant heat conduction from wire to filling material. The energy absorbed from the
resistor in this case results from this simple equation:
QJ = Cs P ΔT where:
- QJ is the quantity of energy expressed in Joule, - Cs is the specific heat of the employed resistance alloy
expressed in J g-1• °K-1, - P is the weight of the wire in grams and - ΔT is the rise of temperature,
expressed in °K, reached by the wire during the impulse.
As type and quantity of wire are characteristics of every resistance value and resistor model, the
acceptable temperature limit of wire is relevant.
This limit (@ 25°C) is:
- 500°C for the standard operations (steady state load);
- 800°C for not repeatable overload.
The following graphs show these two conditions for each resistance value and resistor type.
Pulse Energy
Absorbed energy for wire temperature of 500°C
(Impulse time ≤ 0,2”)
15
14 CFH1100
13
12
11
10
9 CFH750
8
7
6 CFH500
5
4
CFH350
3
2
1
0.2
1
10
100
Resistance (Ohms)
1000
Absorbed energy for wire temperature of 800°C
(Impulse time ≤ 0,2”)
24
22.5
21
19.5
18
16.5
15
13.5
12
10.5
9
7.5
6
4
2
CFH1100
CFH750
CFH500
CFH350
0.2
1
10
100
Resistance (Ohms)
1000
These graphs are irregular owing to the necessity to adapt the commercial dimension of wire to the
resistance range, however they are enough to show the trend of this characteristic.
Should the energy value of an impulse be too close to the limits given from these graphs, it is suitable to
consult the factory for further information concerning the precise value of absorbed energy for the used
resistor.
Literature No. 1773318
Issued: 09-08
Dimensions are shown for
reference purposes only.
Dimensions are in
millimetres unless
otherwise specified.
Specifications subject to
change.
tycoelectronics.com
passives.tycoelectronics.com
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