What's a low leakage current filter from the practical point of view?

TDK-EPC presentation 

What‘s a low leakage current filter 

from the practical point of view? 

Low leakage current requirements in power applications: 

target conflicts and consequences for EMC filter design 

Christian Paulwitz, EPCOS AG, EMC Laboratory, Regensburg, Germany 

EPCOS AG 

A Member of TDK-EPC Corporation 

Magnetics • MAG D&A LAB 

Regensburg, Germany 

June 12, 2012


Who is TDK-EPC? 

Short Company Presentation 

What‘s a low leakage current filter from the practical point of view? • Target conflicts and consequences 

© TDK-EPC 2012 

MAG D&A LAB • 06/12 • 2


TDK-EPC. Global excellence in electronic 

components, modules and systems 

SAE 

Recording Heads 

for HDD 

Electronic 

Components 

TDK-Lambda 

Power Supplies 

Other 

TDK businesses 

ATL 

Batteries 

TDK-EPC 



MAG D&A LAB • 06/12 • 3


TDK-EPC at a glance 

TDK-EPC has emerged from the combination of EPCOS and the electronic components 

business of TDK and markets its products under the product brands, TDK and EPCOS. 

Key info (Fiscal Year 2012, ending March 31) 

Evolution 

Core business 

Headquarters 

Electronic components, 

modules and systems 

Tokyo, Japan 

Munich, Germany 

1935 

TDK (Tokyo Denki Kagaku Kogyo = 

Tokyo Electric and Chemical 

Industries) established in Japan 

to manufacture and commercialize 

ferrites 

Sales 

Number of 

sites 

Employees 

total 

EUR 3.5 billion 

approx. 40, 

more than 50 plants 

43,000 

1999 

2009 

Oct. 1 

EPCOS founded in Germany, 

emerging from Siemens Matsushita 

Components, a joint venture of 

Siemens Passive Components with 

Matsushita 

TDK-EPC Corporation established 

in Japan 



MAG D&A LAB • 06/12 • 4


Broad portfolio of TDK and EPCOS solutions 

• Multilayer Ceramic 

Capacitors 

• Aluminum Electrolytic 

Capacitors 

• Film Capacitors 

• Ferrites 

• Inductors 

• Transformers 

• EMC Components 

• SAW and BAW Filter Products 

• Radio-Frequency Modules 

• ESD/EMI Modules 

• MEMS Products 

• Multilayer High-Frequency 

Components 

• Microwave Ceramic 

Components 

• Piezo 

Devices 

• Thermistors 

• Varistors 

• Surge 

Arresters 

• Sensors 


© EPCOS TDK-EPC AG 2012 

A Member MAG of TDK-EPC D&A LAB Corporation 

• 06/12 • 5 

CC 04/12 • 05


Professional High-End EMC Filters 

Overview standard filters 

1-line filters 

Feedthrough components, up to 500 A 


19 series, 164 types, up to 1000 A 





Filters for shielded rooms 



MAG D&A LAB • 06/12 • 6


Complete Solution Provider for Drive Applications 

Line reactors / PFC 

chokes 

Main 

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DC link 

Inverter 

Dv/dt choke 

Sine-wave 

filter 

Motor 

M 

Ongoing portfolio extension 

Existing portfolio 

EMC filters 

Standard and 

custom specific 

SineFormer TM 

Reduces 

common-mode 

disturbances 



MAG D&A LAB • 06/12 • 7


What‘s a low leakage current filter 

from the practical point of view? 

Low leakage current requirements in power applications: 

target conflicts and consequences for EMC filter design 



MAG D&A LAB • 06/12 • 8


Presentation Structure 

• Leakage current: What do we talk about? 

• Origins of Leakage Current 

• Consequences for EMC filtering 

• Suitability of different measurement procedures 

• Summary 



MAG D&A LAB • 06/12 • 9


Leakage Current: What do we talk about? 

International Electrotechnical Vocabulary: 

“electric current in an unwanted conductive path 

under normal operating conditions” 

Examples for different settings: 

‣ possible direct current through a human body (touch current), 

‣ ensure correct function of protective devices during normal operation 

conditions (residual current), 

‣ Leakage currents reducing installation life time (z. B. bearing currents in 

converter-driven motors), 

‣ High leakage currents in unbalanced and harmonic-containing systems 

(e. g. PEN installations). 



MAG D&A LAB • 06/12 • 10



Physiological effects of the electric current: 

Duration of current flow t 

Zones: 

AC-1 – Imperceptible 

AC-2 – Perceptible 

AC-3 – Reversible 

effects: muscular 

contraction 

AC-4 – Possibility of 

irreversible 

effects. 

Probability of heart 

fibrillation: 

AC-4-1: up to 5 % 

AC-4-2: up to 50 % 

AC-4-3 >50 % 

Current through the body I B 

Source: IEC/TS 60479-1 (2005) 



MAG D&A LAB • 06/12 • 11



Thresholds of protective devices – like RCD – correspond to the areas of 

physiological effects on a human body. 

Note: 

RCD device “30 mA” → tripping threshold approx. 15 mA 

RCD device “300 mA” → tripping threshold approx. 150 mA 



MAG D&A LAB • 06/12 • 12



Typical touch current requirements (maximum current which may flow 

through a human body) for devices : 

3.5 mA (example: for plugable devices, if it is touched while 

the PE conductor might be broken) 

0.5 mA (example: protective class II, medical devices) 



MAG D&A LAB • 06/12 • 13


Origins of Leakage Current 

What is a low-leakage current filter? 

‣ … all EMC filters – as long as no voltage will be applied! 

That means: Leakage current depends not only on filter components, 

but 

‣ … on the power supply voltage (amplitude, frequency, phase balance, 

harmonics content); 

‣ … on the internal voltage sources of the application: 

to be found at switch-mode PWM voltages! 



MAG D&A LAB • 06/12 • 14



Sources, responsible for causing leakage current: 

supply voltage 

EMC filter power electronic application 

mains cable with parasitic 

properties 

leakage current parts, caused 

by supply voltage 

leakage current parts, caused by voltages 

application-internally generated 



MAG D&A LAB • 06/12 • 15



Sources, responsible for causing leakage current: 


EMC filter 

power electronic application 

f mains : n x 50 Hz 

f pulse : 2…16 kHz 

Z L : ~ 0 Typical location 

for residual current 

Z C : large measurements 

(the smaller C the smaller I leak ) 

Z L : according to L: rather large 

Z C : according to C: rather small 

(the larger C the smaller I leak ) 

Note also: leakage current raises at f pulse ~ resonance frequency of L and C 



MAG D&A LAB • 06/12 • 16


Suitability of Different Measurement Procedures 

What are the specific requirements? – Examples: 

1) Limitation of the maximum touch current 

(typical requirements for devices with plugs)? 

2) RCD compatibility 

(in most cases more important requirement at fixed installed 

applications)? 

Attention: 

• One of the requirements does not automatically cover the other one! 

• Definition of operating modes! 

• Definition of setup conditions, which might be relevant for leakage 

currents! 



MAG D&A LAB • 06/12 • 17



Touch current, e. g. according to IEC/EN 60990 (figure 4), weighting with 

regard to perception/reaction: 

100.0% 

A 

B 

1,5 kΩ 

test 

terminal 

500 Ω 

220 nF 

20 kΩ 

Bewertung weighting 

U 1 U 2 

22 nF 

90.0% 

80.0% 

70.0% 

60.0% 

50.0% 

40.0% 

30.0% 

20.0% 

10.0% 

Weighted touch current 

(perception and reaction): 

U 2 

500 Ω 

0.0% 

10 100 1000 10000 100000 

Frequenz [Hz] 

peak value! 

frequency (Hz) 

Example: sinusoidal current of 1 mA / frequency f; measured with perception/reaction network: 

f = 50 Hz => current assessment as „1 mA“ (100 %) 

f = 1 kHz => current assessment as „0,57 mA“ (57 %) 

f = 5 kHz => current assessment as „0,13 mA“ (13 %) 



MAG D&A LAB • 06/12 • 18



An RCD shows quite a similar weighting curve up to the kHz range … 

weighting 

Bewertung gegenüber tatsächlichem Strom 

120% 

100% 

80% 

60% 

40% 

20% 

0% 

10 100 1000 10000 100000 

Frequenz (Hz) 

frequenzy (Hz) 

Abweichung frequencyMessung weighting über curve FI-Nachbildung artificial RCD 

Measured characteristic of an artificial RCD with measurement output 

instead of tripping circuit (Siemens 5SM1 930-0) 



MAG D&A LAB • 06/12 • 19



RCD standardisation for the kHz range; DIN V VDE V 0664-210; 

RCBO (residual current operated circuit-breaker with overcurrent protection) type B+ 

(defined e. g. for DC/AC residual currents up to 20 kHz, pulsed DC residual currents) 

tripping current ranges for RCBO type B+ for frequencies up to 20 kHz 

frequency 

tripping current 

lower limit 

tripping current upper limit 

I Δn : standard value of rated residual current 



MAG D&A LAB • 06/12 • 20



… but in the kHz range the different impedances of the measurement 

apparatus have an influence on the leakage current! 


Z i small 

L1…L3, N 

PE 

EMC filter 

example: 

L = 1 mH 

example: 

C = 10 nF 

power electronic application 

position RCD 

within installation 

Z -> 0 

position measurement 

network for touch current 

50 Hz: Z -> 2 kΩ 

5 kHz: Z -> 600 Ω 

Example with figures for L = 1 mH and C = 22 nF: 

50 Hz: Z(L) -> 0,3 Ω Z(C) -> 300 kΩ 

5 kHz: Z(L) -> 30 Ω Z(C) -> 3 kΩ 



MAG D&A LAB • 06/12 • 21



Example: two frequency converter setups (single phase / 3 phase, ca. 3 kW), 

5 m motor cable, different switching frequencies 

operation 

mode 

Standby 

2 kHz / 50 Hz 

2 kHz / 0.5 Hz 

5 kHz / 50 Hz 

5 kHz / 0.5 Hz 

8 kHz / 50 Hz 

8 kHz / 0.5 Hz 

10 kHz / 50 Hz 

10 kHz / 0.5 Hz 

15 kHz / 50 Hz 

15 kHz / 0.5 Hz 

single phase system 

residual 

current 

3.1 mA 

3.5 mA 

5.3 mA 

3.9 mA 

5.7 mA 

3.7 mA 

11.3 mA 

3.5 mA 

15.4 mA 

3.6 mA 

4.1 mA 

touch 

current 

2.6 mA 

2.7 mA 

3.5 mA 

2.7 mA 

3.6 mA 

2.7 mA 

3.8 mA 

2.7 mA 

3.7 mA 

2.7 mA 

2.9 mA 

3 phase system 

residual touch 

current current 

1.3 mA 1.5 mA 

8.8 mA 2.0 mA 

12.8 mA 4.0 mA 

7.4 mA 1.7 mA 

25.5 mA 3.7 mA 

4.4 mA 1.7 mA 

12.0 mA 3.0 mA 

4.2 mA 1.6 mA 

7.2 mA 2.5 mA 

4.3 mA 1.6 mA 

5.0 mA 1.9 mA 

Comparison: touch current measurement vs. residual-current-operated protection device 

Validation: Does the RCD not trip, 

if the touch current requirement of 3.5 mA is met? 



MAG D&A LAB • 06/12 • 22



Example: two frequency converter setups (single phase / 3 phase, ca. 3 kW), 

5 m motor cable, different switching frequencies 

Comparison: touch current measurement vs. RCD 

5 

4.5 

4 

Berührstrom touch current [mA] 

3.5 

3 

2.5 

2 

1.5 

1 

0.5 

0 

0 5 10 15 20 25 30 

residual Fehlerstrom current [mA] 

Standby 2 kHz 5 kHz 8 kHz 10 kHz 15 kHz 



MAG D&A LAB • 06/12 • 23


Summary 

• Specification of leakage current requirements: 

- definition of targets 

- choice of the suitable measurement procedure; maybe more than one 

might be necessary. 

• Initiators of leakage currents: 

- power supply of the application (power frequency) 

- switch-mode voltages generated by the application (usually kHz range) 

Filter components do not cause leakage currents but influence them 

depending on the initiator. 

• Matching EMC filters to leakage current requirements:: 

- power supply voltage limits capacitance to ground 

- higher frequency parts of the leakage current require then 

big filter inductances 

- considering filter resonances => inductances might have to get even bigger 

=> The more restrictive the requirements, the bigger and the more expensive the 

filter. 



MAG D&A LAB • 06/12 • 24


Contact 

Christian Paulwitz 

EPCOS AG 

A Member of TDK-EPC Corporation 

EMC Laboratory 

Wernerwerkstraße 2 

D-93049 Regensburg 

Germany 

Telephone: +49 941 850 6107 

Fax: +49 941 850 6110 

christian.paulwitz@epcos.com 

www.global.tdk.com · www.epcos.com 

Bart van den Broek 

BMF System Parts BV 

Gulberg 43 A 

5674 TE Nuenen 

The Netherlands 

Telephone: +31(0)40-8512170 

Fax: +31(0)40-8512171 

info@bmf-systemparts.com 

www.bmf-systemparts.com 



MAG D&A LAB • 06/12 • 25


www.tdk-epc.com

What's a low leakage current filter from the practical point of view?

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