NTC thermistors for
inrush current limiting
Leaded and coated disks
Series/Type:
Date:
B57237
May 2009
© EPCOS AG 2009. Reproduction, publication and dissemination of this publication, enclosures hereto and the
information contained therein without EPCOS' prior express consent is prohibited.
Inrush current limiters
ICLs
B57237
S237
Applications
Switch-mode power supplies
Soft-start motors, e.g. in vacuum cleaners
Features
Useable in series connections
up to 265 V
RMS
Coated thermistor disk
Kinked leads of tinned copper wire
Wide resistance range
UL approval (E69802)
Options
Resistance tolerance <20% and alternative
lead configurations available on request
Delivery mode
Bulk (standard),
cardboard tape, reeled or in Ammo pack
General technical data
Climatic category
Max. power
Resistance tolerance
Rated temperature
Dissipation factor
Thermal cooling time constant
Heat capacity
(IEC 60068-1)
(at 25
°C)
Dimensional drawing
Dimensions in mm
Approx. weight 2 g
(in air)
(in air)
P
max
∆R
R
/R
R
T
R
δ
th
τ
c
C
th
55/170/21
3.1
±20
25
approx. 17
approx. 90
approx. 1530
W
%
°C
mW/K
s
mJ/K
Electrical specification and ordering codes
R
25
Ω
1
2.2
2.5
4.7
5
7
10
15
22
33
60
I
max
(0...25
°C)
A
9.0
7.0
6.5
5.1
5.0
4.2
3.7
3.0
2.8
2.5
1.6
B
25/100
K
2700
2800
2800
2900
2900
3000
3060
3000
3300
3300
4000
C
test1)
230 V
µF
700
700
700
700
700
700
700
700
700
900
400
C
test1)
110 V
µF
2800
2800
2800
2800
2800
2800
2800
2800
2800
3600
1600
Param.
for R(I)
1)
k
0.622
0.806
0.843
1.03
1.05
1.16
1.29
1.49
1.57
1.78
1.77
Param.
for R(I)
1)
n
1.27
1.30
1.30
1.32
1.32
1.33
1.34
1.33
1.37
1.37
1.44
Ordering code
B57237S0109M000
B57237S0229M000
B57237S0259M000
B57237S0479M000
B57237S0509M000
B57237S0709M000
B57237S0100M000
B57237S0150M000
B57237S0220M000
B57237S0330M000
B57237S0600M000
1) For details on the capacitance C
test
as well as on the parameters k and n refer to "Application notes", chapters 1.6 and 1.7.
Please read
Cautions and warnings
and
Important notes
at the end of this document.
Page 2 of 15
Inrush current limiters
ICLs
B57237
S237
Reliability data
Test
Storage in
dry heat
Standard
IEC
60068-2-2
Test conditions
∆R
25
/R
25
(typical)
< 10%
Remarks
No visible
damage
Storage in damp
heat, steady state
Rapid temperature
cycling
Endurance
Cyclic
endurance
Transient
load
Note
Storage at upper
category temperature
T: 170
°C
t: 1000 h
IEC
Temperature of air: 40
°C
60068-2-78 Relative humidity of air: 93%
Duration: 21 days
IEC
Lower test temperature: 55
°C
60068-2-14 Upper test temperature: 170
°C
Number of cycles: 10
I = I
max
t: 1000 h
I = I
max
, 1000 cycles
On-time = 1 min
Cooling time = 6 min
Capacitance = C
test
Number of cycles: 1000
< 5%
No visible
damage
No visible
damage
No visible
damage
No visible
damage
No visible
damage
< 10%
< 10%
< 10%
< 5%
The self-heating of a thermistor during operation depends on the load applied and the
applicable dissipation factor.
When loaded with maximum allowable current/power and the specified dissipation factor is
taken as a basis, the NTC thermistor may reach a mean temperature of up to 250
°C.
The heat developed during operation will also be dissipated through the lead wires. So the
contact areas, too, may become quite hot at maximum load.
When mounting NTC thermistors you have to ensure that there is an adequate distance
between the thermistor and all parts which are sensitive to heat or combustible.
Please read
Cautions and warnings
and
Important notes
at the end of this document.
Page 3 of 15
Inrush current limiters
ICLs
B57237
S237
Taping and packing
1
Taping of radial leaded NTC thermistors
Dimensions and tolerances
Lead spacing F = 5.0 mm
(taping to IEC 60286-2)
Lead spacing F = 7.5 mm
(taping based on IEC 60286-2)
Please read
Cautions and warnings
and
Important notes
at the end of this document.
Page 4 of 15
Inrush current limiters
ICLs
B57237
S237
Dimensions (mm)
Lead
spacing
5 mm
w
th
d
P
0
P
1
F
∆h
∆p
W
W
0
W
1
W
2
H
H
0
H
1
D
0
t
L
L
1
11.5
6.0
0.5/0.6
12.7
3.85
5.0
0
0
18.0
5.5
9.0
3.0
18.0
16.0
32.2
4.0
0.9
11.0
4.0
Tolerance of
lead spacing
5 mm
max.
max.
±0.05
±0.3
±0.7
+0.6/ 0.1
±2.0
±1.3
±0.5
min.
+0.75/ 0.5
max.
+2.0/ 0
±0.5
max.
±0.2
max.
max.
max.
Lead
spacing
7.5 mm
21
7
0.8/1.0
12.7
8.95
7.5
0
0
18.0
11.0
9.0
3.0
18.0
16.0
45.0
4.0
0.9
11.0
4.0
Tolerance of
lead spacing
7.5 mm
max.
max.
±0.05
±0.3
±0.8
±0.8
Depends on th measured at top
of component body
±2.0
±0.5
min.
+0.75/ 0.5
max.
+2.0/ 0
±0.5
max.
±0.2
max.
max.
max.
without wires
peel-off force
≥5
N
±1
mm / 20 sprocket holes
Remarks
Please read
Cautions and warnings
and
Important notes
at the end of this document.
Page 5 of 15
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