Application notes
The following two important aspects for determining the right NTC inrush current limiter are
excerpted from the chapter "Application notes" in the "NTC Inrush Current Limiters,
Data book 2012". The complete application note can be downloaded from
www.epcos.com/ntcicl_appnotes.
1.4 Load derating
The power handling capability of an NTC thermistor cannot be fully utilized over the entire temper-
ature range. For circuit dimensioning the derating curve given below provides information on the
extent to which the current must be reduced at a certain ambient temperature (T
A
).
Derating curve for types S237, P11 and P13
Figure 1
T
A
= Ambient temperature > 25 °C
T
max
= 170 °C
Derating curve for types S153, S235, S236, S238, S364 and S464
Figure 2
Inrush current limiters B57364S0***M0**
ICLs S364
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Important notes at the end of this document.
T
A
= Ambient temperature > 65 °C
T
max
= 170 °C
The I
max
values specified in the data sheets denote the maximum permissible continuous current
(DC or RMS values for sine-shaped AC) in the temperature range 0 °C to 65 °C.
1.6 Maximum permissible capacitance
The currents during turn-on are much higher than the rated currents during continuous operation.
To test the effects of these current surges EPCOS uses the following standard procedure accord-
ing to IEC 60539-1:
Figure 3
Test circuit for evaluating the maximum permissible capacitance of an NTC thermistor
V
load
Load voltage [V]
C
test
Test capacitance [µF]
R
S
Series resistance [R
S
= 1 ]
V
NTC
Voltage drop across the NTC under test [V]
The capacitor C
test
is discharged via the series resistor R
S
and the NTC inrush current limiter. The
load voltage is chosen such that the voltage applied to the thermistor at the start of discharge is
VNTC = 375 V (corresponds to (230 V + V) 2).
Inrush current limiters B57364S0***M0**
ICLs S364
Page 8 of 20Please read Cautions and warnings and
Important notes at the end of this document.
Figure 4
Maximum permissible capacitance discharging test: typical curves
The maximum capacitances that can be switched depend on the individual thermistor type and
are given in the data sheets.
Inrush current limiters B57364S0***M0**
ICLs S364
Page 9 of 20Please read Cautions and warnings and
Important notes at the end of this document.

B57364S0409M051

Mfr. #:
Manufacturer:
EPCOS / TDK
Description:
ICL 4 OHM 20% 9.5A 21MM
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