Basic Principals of Inrush Current Limiting
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Transcript of Basic Principals of Inrush Current Limiting
EPCOS AGA Group Company of TDK-EPC Corporation
PPD • PD VAR PMMunich, Germany
Feb 2010
Protection Devices
Inrush Current Limiting NTCs
© TDK-EPC Corporation 2010 PPD PD VAR PM • 01/10 • 2Protection Devices: ICL Basis
Protection devices
• Overload protection
• Telecom line protection
• Surge voltage protection at Telecom installations and AC lines
• PTC relays for compressors start
• LED current regulation
• Heating elements
• Inrush current limiting
Major applications
» Surge arresters
» PTC elements
» Disk varistors
» ICLs
© TDK-EPC Corporation 2010 PPD PD VAR PM • 01/10 • 3Protection Devices: ICL Basis
Inrush Current Limiters from EPCOS.
A safe and reliable protection for capacitive loads in switching circuits and for soft
starting of inductive loads.
ICLs - The Safe Start
© TDK-EPC Corporation 2010 PPD PD VAR PM • 01/10 • 4Protection Devices: ICL Basis
Principle of ICL-NTCs
Resistance / Temperature Curve
R
TTypical load current characteristic
© TDK-EPC Corporation 2010 PPD PD VAR PM • 01/10 • 5Protection Devices: ICL Basis
ICL - Inrush Current Limiting
Reducing of inrush current in order ...
� to reduce the peaks in the circuit
� to protect other components
� to avoid tripping of fuses
� to reduce PCB size compared to
fixed resistors
Inrush Current Limiting in
� Switched Mode Power Supplies
� Soft Start of Electric Motors
� Halogen Lamps
� Fluorescent Lamps
� Transformers
© TDK-EPC Corporation 2010 PPD PD VAR PM • 01/10 • 6Protection Devices: ICL Basis
• Wide product range12 various ceramic systems
Rated resistance(25°C) : 1 up to 80 [ohm]
Max. permissible current : 1.3 up to 20.0 [A]
• No current derating in the range of 0 to 65°C
(except S237)
• High reliability
Tested according to IEC 60068 (dry heat, damp heat,
rapid temperature cycling)Endurance, pulse strength are proved.
UL approval (E69802)
• Inside- and outside kink lead are also available
(Inline kink lead is standard.)
ICL – Advantages
© TDK-EPC Corporation 2010 PPD PD VAR PM • 01/10 • 7Protection Devices: ICL Basis
Series 0.1 1.0 10.0 100.0 Ohm
B57153S
B57235S
B57236S
B57237S
B57238S
B57364S
B57464S
ICL Product Families
© TDK-EPC Corporation 2010 PPD PD VAR PM • 01/10 • 8Protection Devices: ICL Basis
ICLs: Structure and Principle
Sintering various oxide together with other additives produces a polycrystalline, semi-conductive, temperature depending ceramic.
This phenomenon results in a Negative Coefficient Thermistor (NTC)
R/T characteristics of a NTC
R
T
© TDK-EPC Corporation 2010 PPD PD VAR PM • 01/10 • 9Protection Devices: ICL Basis
Circuit Principle
The ICL is placed in series with the load
before the capacitive or inductive load. The
NTC thermistors specifically developed for
this application limit the current at turn-on by
their relatively high cold resistance. As a
result of the current load the thermistor heats
up and reduces it‘s resistance.
Hence the ICL provides protection from
undesirable high inrush currents but features
low power consumption during continuous
operation.
© TDK-EPC Corporation 2010 PPD PD VAR PM • 01/10 • 10Protection Devices: ICL Basis
Principle of ICL-NTCs
The thermal properties of a Power
NTC can be used to limit harmful
switch-on currents of capacitive loads.
At turn-on the NTC restricts the
current flow into the capacitor due to its `cold` resistance. The current
flowing through the NTC causes it to
self heat and thereby reducing its
resistance by a factor 10 to 50.
© TDK-EPC Corporation 2010 PPD PD VAR PM • 01/10 • 11Protection Devices: ICL Basis
Load Derating of ICLs
Derating curve for maximum permissible continuous
current vs ambient temperature
Circuit Examples
© TDK-EPC Corporation 2010 PPD PD VAR PM • 01/10 • 13Protection Devices: ICL Basis
Typical Power Supply (Line – Line)
Input protected by Varistor against over-voltages.
Capacitor protected against inrush-currents by an ICL.Load fuse additionally used to protect the Varistor against thermal runaway.
~
VaristorICL
© TDK-EPC Corporation 2010 PPD PD VAR PM • 01/10 • 14Protection Devices: ICL Basis
Power Supply with Relay (Line-Line)
Sensing circuit shorts-out the ICL when the capacitor has reached a pre-determined voltage i.e. 95% of charge..
~
VaristorICL
© TDK-EPC Corporation 2010 PPD PD VAR PM • 01/10 • 15Protection Devices: ICL Basis
Protection of Drives and Invertors
Block Varistors protect each phase of Drive
ICLs protect the Capacitors
DC-Link
InverterRectifier
M
MotorMains
Fields of Application
© TDK-EPC Corporation 2010 PPD PD VAR PM • 01/10 • 17Protection Devices: ICL Basis
Disks in Entertainment Electronics
A guideline for the selection of types
for this application.
VAR S05 – S20,
ETFV, SFS
175V / 275VICL S153, S236, S237
4.7 / 10.0 Ohm
© TDK-EPC Corporation 2010 PPD PD VAR PM • 01/10 • 18Protection Devices: ICL Basis
Disks in Consumer Electronics
A guideline for the selection of types for this application.
VAR S05 – S20,
275V / 300V
ICL S153 – S364
© TDK-EPC Corporation 2010 PPD PD VAR PM • 01/10 • 19Protection Devices: ICL Basis
Disks in Power Supplies
Varistors
S10K385 / 420 / 510 (E2)
S14K385 / 420 / 510 (E2)S20K385 / 420 / 510 (E2)
SMPS / UMPS Energy-Meter
Varistors
S++K175 / 275 (E2)
SFS; ETFVICLS153; S235;S236
Compressor
Varistors
S++K175 - 420 (E2)
SFS; ETFVICLS153;S235;S236
www.tdk.co.jp • www.epcos.com