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

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