EMI Filter
EMI Filter
1 Noise Basics
1 Noise Basics

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What Is Noise?
What Is Noise?
Noise Sources
Noise Sources
What Is EMC?
What Is EMC?
Propagation Paths of Noise
Propagation Paths of Noisea. Conductive noise
a. Conductive noiseb. Inductive noiseb. Inductive noisec. Radiated noisec. Radiated noise
Basics of Noise Reduction
Basics of Noise Reduction
Types of Conductive Noise
Types of Conductive Noise
Types of and Countermeasures for Noise
Types of and Countermeasures for Noisea. High-frequency noise
a. High-frequency noiseb. Pulse noiseb. Pulse noisec. Surge noisec. Surge noise

2 Selection of EMI Filters
2 Selection of EMI Filters

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3 How to Use EMI Filters
3 How to Use EMI Filters

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2

Ground Wiring
Ground Wiring
Input and Output Wiring
Input and Output Wiring

4 Noise Reduction
4 Noise Reduction

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2
2
3
3
4
4

Input and Output Impedance and Filter Circuit
Input and Output Impedance and Filter Circuit
EMI Filter Installation and Orientation
EMI Filter Installation and Orientation
Combining Multiple EMI Filters
Combining Multiple EMI Filters
External Ferrite Core
External Ferrite Core

5 EMC Test
5 EMC Test

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CE Marking
CE Marking

a. Machinery directive
a. Machinery directive
b. EMC directive
b. EMC directive
c. Low voltage directive
c. Low voltage directive
Conducted Emission
Conducted Emission
Radiated Emission
Radiated Emission
Power Supply Harmonic Current
Power Supply Harmonic Current
Electrostatic Discharge
Electrostatic Discharge
Radio frequency electromagnetic field
Radio frequency electromagnetic field
Fast Transient/Burst
Fast Transient/Burst
Surge
Surge
Conducted Radio-frequency Interference
Conducted Radio-frequency InterferencePower Frequency Magnetic Field
Power Frequency Magnetic Field
Voltage Dip/Momentary Power Interruption
Voltage Dip/Momentary Power Interruption
Unit of Noise
Unit of Noise
Detection Method a. Peak detection
Detection Method a. Peak detection
b. Quasi-peak detection
b. Quasi-peak detection
c. Average detection
c. Average detection
Noise Terminal Voltages, Radiated Emission Limits (Extractions)
Noise Terminal Voltages, Radiated Emission Limits (Extractions)
Terminology related to EMC Test
Terminology related to EMC Test

Rated Voltage
Rated Voltage
Rated Current
Rated Current
Test Voltage (Withstand Voltage)
Test Voltage (Withstand Voltage)
Insulation Resistance (Isolation Resistance)
Insulation Resistance (Isolation Resistance)
Leakage Current
Leakage Current
DC Resistance
DC Resistance
Temperature/Humidity
Temperature/Humidity
Circuitrya. Single-phase one-stage filter
Circuitryb. Single-phase two-stage filter
a. Single-phase one-stage filter
Safety Standards
b. Single-phase two-stage filter
a. Overview of safety standards
Safety Standards
b. Safety standards for EMI filtersa. Overview of safety standardsc. CCC approval from China
14b. Safety standards for EMI filters
14
Attenuation Characteristic (Static Characteristic)
15
c. CCC approval from China
15
Pulse Attenuation Characteristic
Attenuation Characteristic (Static Characteristic)
Ground Capacitor Codes
Supplement
Pulse Attenuation Characteristic
Supplement
Optionsa. DIN rail installation type
1 Source Voltages in the World
Ground Capacitor Codesb. Terminal block type
1 Source Voltages in the World
Options a. DIN rail installation typec. High permeability choke coil typeb. Terminal block typed. Hexagon socket head cap bolt typec. High permeability choke coil typee.With switch of line to ground capacitor typed. Hexagon socket head cap bolt type
f.Improve differential mode attenuation typee.With switch of line to ground capacitor typeg.Ultra high attenuation type for EU
f.Improve differential mode attenuation typeh.High input voltage typeg.Ultra high attenuation type for EU
July 21, 2022

6
6Technical Notes-1

1 Noise Basics
1 What Is Noise?

3 What Is EMC?

Noises refers to unwanted variations or fluctuations involtage, current, signals, etc.

EMC stands for electromagnetic compatibility, and refers
to the ability of electrical equipment to have both EMI
and EMS at once; the former indicates the ability tosuppress noise radiated from the equipment itself andthe latter means the ability to endure noise from otherequipment.

E
E
GND

What a designer expects(an ideal steady voltage
source)What are EMC compliant products?
The EMC compliant products refer to those that meetstandards required by EMI and EMS.
They provide various types of parts that can deal withnoise from the viewpoint of EMI and/or EMS.
Our noise filters (hereinafter, “EMI filters”) are parts thatmainly deal with conducted interference in terms of EMI.

In reality, noises are included.

Figure 1.1.1 What Is Noise?

2 Noise Sources

EMC = EMI + EMS

Noise comes in two types: natural noise and manmade noise.
While natural noises are generated by a lightning strikeor static electricity, manmade noises are generated byfamiliar devices such as industrial equipment, fluorescent bulbs, or communication equipment.

EMI
ElectroMagnetic
Interference

Lightning strike, static electricity,
cosmic ray

Natural
Noise

Noise

Conducted Interference

ManmadeNoise

Discharge noise due to fluorescentbulbs, etc., switching noise due toinverters and switching powersources, radio communicationequipment, radio waves transmitted
for broadcasts, wireless LAN,cell
phones

EMC
ElectroMagnetic
Compatibility

Figure 1.2.1 Noise Sources
Typical devices that generate noise are switching
power sources and general-purpose inverters.
Such devices include switching elements such as
FETs and IGBTs, and are major noise sources due tohigh-frequency switching of those elements.
Inverter
circuitDC AC

SmoothingcircuitDC

Rectification
circuit
AC DC

Sub power
supplycircuit

Motor

M

Control
circuitFigure 1.2.2 Inverter block diagram
T1

D1
T1
C1

T3

T5

RL

M

VCC
TR1
T2

Figure 1.2.3 Sub power supply
inverter operation waveform

Technical Notes-2

T4

T6

Figure 1.2.4 Inverter
PWM output waveform

July 21, 2022

Noise propagated andleaked from power lines

Radiation Interference
Noise radiated from chassis,
cables, etc.

Conducted Immunity

EMS
ElectroMagnetic
Susceptibility

Surge: Noise such as one
due to lightning strikes

Radiation Immunity
Radiation field: Noise such as
one due to radio equipment

Figure 1.3.1 Concept of EMC

1 Noise Basics
4 Propagation Paths of Noise

6 Types of Conductive Noisea. Conductive noise
Refers to noise that propagates through a power line or
PCB tracing.

Noise is divided into two types based on its generation mode: normal mode noise and common modenoise. Normal mode noise is also called differential
mode noise, and refers to noise generated between
power lines. Common mode noise refers to noise
generated between a power line and ground line.

b. Inductive noise
Refers to noise that is induced due to electromagnetic
or electrostatic induction caused by a power line or asignal line of a peripheral device when it is placednear a line or pattern in which noise current flows andpropagates through the line.
c. Radiated noise
Noise radiated by an antenna (or a line be having as
an antenna) that propagates to other devices throughthe air.
PowersupplyOther apparatus[Normal Mode]

Power electronics devices(inverters and switching
power source)

7 Types of and Countermeasures for Noise

Load

a. High-frequency noise

Inductive noise

Other apparatus

Kinds of Noiseb. Pulse noise

Conductive noise
Other apparatus

c. Surge noise

Figure 1.4.1 Propagation Paths of Noise

5 Basics of Noise Reduction
The propagation of noise consists of a noise source,
an entity that is affected by the noise, and propagation path that connects both. To reduce noise:
Reduce the noise level of a noise source
Make it more difficult for noise to propagate
Make equipment less vulnerable to noise
In addition to the abore, designs must consider
standards, quality and cost of noise reduction methods.

Propagation
Paths

Noise source

Input

Noise
sourceInput

Power sourcemachineFigure 1.6.1 Noise Generation Paths(Example in which a noise source is within power equipment)

Radiated noise

Noise Sources[Common Mode]

Power sourcemachineEquipment affectedby a noise failure

a. High-frequency noise
Also called EMI noise or power supply noise andrefers to high-frequency components such as theclock frequency of a computer and switchingfrequency of power sources. As an antinoise
measure, an EMI filter should be installed on the
input side. An appropriate filter should be selectedbased on requirements such as attenuation, mechanical design and cost.
EMI Filter

MotordriverLINE LOAD

100
90

EN55011 Group2 ClassA

QP

80

AV

Level [dBµV]

70

Figure 1.5.1 Overview of Noise Generation
and Propagation Path

Motor

60

No EMI Filter

50
40
30

With EMI Filter

20
10
0
0.1

1

Frequency [MHz]

10

100

Figure 1.7.1 Example of Noise Reduction
by an EMI Filter

July 21, 2022

Technical Notes-3

1 Noise Basics
Output ripple noise from a switching power sourceis also a type of high-frequency noise.
Ripple noise can be reduced with a DC filter designed
fot it.
Switchingpower
supplyLCA50S-12

EMI Filter
IN

Load

OUT

LCA50S-12+SNA-06-223

10mV/DIV 4µ s/DIV

Normal temperature,
Normal humidit
BW:500MHz
LCA50S-12
12V 4.3A

10mV/DIV 4µ s/DIVc. Surge noiseThis noise occurs when a natural discharge (such as
lightning) affects a power line. As the generated
voltage reaches as extremely high as a few kilovoltsor more, EMI filters cannot suppress surge noise. Asan antinoise measure, one could use a part such as avaristor to control surge voltage between power lines
or between a power line and ground. EMI filters canwithstand approximately 2 kV between power lines
and approximately 4 kV between a power line andground (these values are not guaranteed).
If surges are a concern, surge countermeasures
should be selected and installed to handle the EMI
filter’s capabilities.
EMI Filter

Figure 1.7.2 Example of Effectivemess of
Ripple Noise Filter

LINE LOAD

b. Pulse noiseThis noise is generated when a relay or motor is driven.
As peak voltage may reach as high as a few thousand
volts, generic filters may not be able to sufficiently
attenuate noise because its choke coil gets saturated.
As an antinoise measure, one could select a filter thatuses an amorphous core for its superior pulse attenuation characteristic.
Pulse noise

EMI Filter

LINE LOAD

Electronic
control
apparatus[Pulse attenuation characteristic Pulse width: 11µs]
Output voltage [V]

200

100

0

0

0.2

0.4

0.6

0.8
1.0
1.2
Input voltage [kV]

1.4

1.6

1.8

2.0

Figure 1.7.3 Example of Pulse Attenuation
Characteristic(NAP-16-472)

Technical Notes-4

July 21, 2022

Electronic
control
apparatus

Anti-surge Parts
Figure 1.7.4 Proper Installation Location ofsurge Countermeasvres

2 Selection of EMI Filters
1 Rated Voltage

3 Test Voltage (Withstand Voltage)

The rated voltage is the maximum line voltage(nominal value) allowable to be used.
As the rated voltages for some parts used within an
EMI filter are high in reality, however, voltages higher
than the rated voltage of the EMI filter may be usedwithout causing any trouble.
In fact, the rated voltages of filter components areoften higher, in which case the filter can handle actual
voltages that exceed its ratins.
In the case of some EMI filters, the maximum operation voltages are defined by specifications for them,separately from rated voltages.
Note that using EMI filters at voltages lower than theirrated voltages do not pose any problems. For
example, an EMI filter with a rated voltage of AC 250 V
can be used for power lines of AC 100V.

The test voltage is a voltage value that is applied at
the time of withstand voltage test. The withstandvoltage test is to verify that the part does not breakwhen applying a high voltage in a short period of time
between a terminal (line) and the mounting plate(ground) of an EMI filter.
In the case of EMI filters for AC power lines, the test
voltage is generally AC 2000 V or AC 2500 V.

As for line frequency, EMI filters for AC power supply
lines have been basically designed to be used with thecommercial frequency (50 Hz/60 Hz).
Higher frequencies such as 400Hz can cause
problems such as excessive capacitor heating.
Note that EMI filters for AC power lines can also be
used for DC power supply lines.

2 Rated Current
The rated current is the maximum load current(nominal value) that can be continuously carried. If theambient temperature is high, however, the load current
needs to be derated.
Figure 2.2.1 shows an example of a derating characteristic.
100

Load factor[%]

80
60
40
20
0
-40

-30

-20

40

50 55 60

Ambient air temperature[

70

80

90

]

Figure 2.2.1 Derating Curve
This example indicates that when the maximum ambient
temperature reaches 75 , the EMI filter should be usedwith a load factor of approximately 60% (approximately
60% of the rated current) or lower.
Current higher than the rated current would be allowed toflow in EMI filters for a short period of time only. Inrush
current (Up to 40A or 10 times the rated current, single
shots with a length of a few milliseconds) from devices
such as a general switching power source does not cause
any problems, but relatively long and / or repetitive peakcurrent draws can result in the average current exceeding
the filter’s raring.

In withstand voltage tests, the high voltage applied
between a line and ground, results in abnormally highleakage current flow. When carrying out a withstandvoltage test in an acceptance inspection, please set
the cutoff current of withstand voltage test equipment
to an appropriate value (the cutoff current defined in
the specifications for the EMI filter).
For some EMI filters that have ground capacitors withextremely large capacity, DC voltages may be used fortest voltages because the leakage current becomes
too high when AC voltages are applied.

4 Insulation Resistance (Isolation Resistance)
Insulation resistance is a resistance value when applying a specified DC voltage (normally 500 V) between
isolated conductors such as a terminal (line) and themounting plate (ground), and regarded as one indicatorof degree of insulation.
The insulation resistance is found by measuring thevery small current that flows in an insulating material
such as a resin case and capacitor when DC voltage isapplied.

5 Leakage Current
The leakage current is an electric current that flows
from the ground terminal of an EMI filter when thefilter is connected to an AC power line.
Generally, as one sets the capacitance of a groundcapacitor to a higher value, the reduction effect oncommon mode noise will be heightened and at thesame time, the leakage current will increase.
Care must be taken, because large leakage current
could cause a circuit breaker to trip or electric shock
to occur when the EMI filter is not properly grounded.
Current ( ) that flows from each power line to groundis represented with the following expression; it forms
the basis of leakage current calculation.

July 21, 2022

f : Power frequency
C : Capacitance between line
and groundE : Power supply voltage
between line and ground

Technical Notes-5

2

Selection of EMI Filters

6 DC Resistance

8 Circuitry

DC resistance is a resistance value between the input
and output of an EMI filter (the sum of resistancevalues for both directions).
It is mostly accounted for with the coil resistances
but also includes connections between the coils andterminals.
The voltage drop caused by an EMI filter is represented
with the following expression:

The following represents examples of EMI filter circuit
structures.

Voltage drop = DC resistance x Load current

a. Single-phase 1-stage filter
Case

L

1

3
CY

LINE

R

CX

CY

2

Note that specifications for some products define
voltage drops when rated current is carried, instead ofresistance values.

LOAD

CX

4

Figure 2.8.1 Circuit Structure Example ofa Single-phase 1-stage EMI Filter

7 Temperature/Humidity

This figure shows a standard circuit structure forsingle-phase EMI filters.
L and CYs reduce the common mode noise; CXs
and leakage inductance from L reduce the normal
mode noise.
R indicates a discharge resistance for capacitors.

a. Operating temperatureThis is the range of ambient temperatures for which the
product’s usage is guaranteed.
If an ambient temperature is high, the load current needs
to be derated.
b. Operating humidity
This is the range of ambient humidities for which the
product’s usage is guaranteed.
It assumes no condensation.
c. Storage temperature and humidity
The specified ranges of ambient temperatures andhumidities that EMI filters in an unenergized state canbe stored without deteriorating performance. No
condensation is assumed for the storage humidity.

b. Single-phase 2-stage EMI filter
Case

L

1
LINE

L

3

CY

R

CX

CX
CY

2

LOAD
4

Figure 2.8.2 Circuit Structure Example ofa Single-phase 2-stage EMI filter
The above figure represents a circuit structure
example of placing choke coils in two stages toimprove the attenuation characteristic.
The following graph shows an example comparisonof attenuation characteristics for a 1-stage and2-stage EMI filter.
[Common Mode]01020
Attenuation [dB]

30
40
50
60
70
80
90
100
110
00.1

0.1

NAC-06-472
1-stageTechnical Notes-6

1Frequency [MHz]

10

100

NBC-06-472
2-stage

Figure 2.8.3 Example of Comparing Attenuation Characteristics
between 1-stage and 2-stage EMI filters.
July 21, 2022

2

Selection of EMI Filters
 ENEC

9 Safety Standards
a. General description of safety standards
The international standards consist of IEC standards
which concern the electrical fields, and ISO standards
which concern the non-electrical fields.
 IEC(International Electrotechnical Commission)Standardization organization for standards related
to the electrical fields; its headquarters is locatedin Switzerland.
It releases technical standards for electricity basedon the latest sciences and technologies, and eachcountry develops its own specific safety standards
based on the corresponding
IEC standards.

 CISPR(Comite International Special desPerturbations Radioelectriques=International Special Committeeon Radio Interference)
One of IEC’s special committees; it was establishedwith the aim to integrate standards such as allowablevalues and measurement methods for interferingwaves causing radio communication failures, andincludes a standardization committee for EMC(Electro Magnetic Compatibility).

 European Standard / EN Standard(Europaische Norm=European Standard)
The EN Standard was created based on the IEC andCISPR standards, and consists of items almost
similar to those in both standards.
A unique number is assigned to each standard.
(Exampla:IEC939 EN60939)[An example of Certification Authorities
in Europe based on EN Standard]

VDE

Germany

TUV

Germany

DEMKO

Denmark

SEMKO

Sweden(European Norm Electrical Certification)
The safety approval mark in Europe that enables
products to smoothly be delivered among all theEU signatories, EFTA (European Free Trade Area),and East European countries.
Electronic products that are authorized to bear the
ENEC mark do not need to be subjected to application
procedures among the signatories. It provides abenefit of eliminating the need to obtain approval
from each signatory to which they are distributed.
The ENEC mark is intended to apply to products
such as lighting equipment, transformers, information
processing equipment, switches and EMI filters.
EU signatories … Germany, UK, Italy, Denmark,and 24 other countries
EFTA……… Iceland, Norway, Switzerland,and Lichtenstein
East European…Ukraine, Estonia, Belorussia,
countries
Moldova, Latvia, and Lithuania

 North America

UL (Underwriters Laboratories Inc.)

A test organization established in 1894 by theElectrical Bureau of the National Board of Fire
Underwriters. Since then, it has been performing
compliance tests on various electric products.
CSA (Canadian Standard Association)
A non-profit standardization organization establishedin Canada in 1919. Each state law in Canadarequires that electric equipment that needs to beconnected to a public power source conforms to the
CSA standards.

UL

USA

CSA

CanadaAs the US and Canada have signed MRA (Mutual
Recognition Agreement), mutual approval can beobtained. If UL verifies that a certain electric productconforms to the CSA standard, or to the UL andCAS standards, the product is authorized to bear thefollowing approval marks:
CSA
UL,CSA

EN Standard:
Europe standard
signStandard classification number
EN50000 series
EN55000 series
EN60000 series

Sequence
numberStandard classification
number
Reference standards
General European standards
CISPR standards
IEC standards

b. Safety standards for EMI filters
Different products may conform to different safety
standards and bear different approval marks (for use
in different countries). Check the approved safety
standards when considering purchasing them.
IEC939EN60939
UL1283
C22.2 No.8

International standard
EU
USA
Canada

IEC
EN
UL
CSA

c. CCC approval from China
EMI filters do not fall within the scope of CCC.
(as of November 2011)

July 21, 2022

Technical Notes-7

2

Selection of EMI Filters
010 Attenuation Characteristic (Static Characteristic)

Attenuation = 20Log10 (U01/U02) [dB]
U01:Generated voltage when a EMI filter is not inserted [V]
U02:Generated voltage when a EMI filter is inserted [V]*An attenuation of 20 [dB] means that the noise level
reduces to 1/10 of the one without an EMI filter.
Similarly, 40 [dB] and 60 [dB] mean a 1/100 and
1/1000 reduction of the noise level, respectively.

Bas-Rhin

Bas-Rhin20
30

Attenuation [dB]

Attenuation characteristic provides a rough indication ofnoise reduction effect. The graph is derived from plotting
an attenuation characteristic when connecting a EMI
filter to a specified measurement circuit with frequency
on the horizontal axis and with attenuation on thevertical axis.
The measurement methods are shown in Figure 2.10.1
and Figure 2.10.2. The attenuation is given as the ratioof U01 to U02, where U01 is output when EMI filters are
not in the measured circuit and U02 is when an EMI filter
is in the circuit, and normally expressed with the logarithmof that ratio in [dB].

10

40
50
60
70
80
90
100
110
120
0.1

1

Frequency [MHz]Normal Mode

10

100

Common Mode

Figure 2.10.3 Example of Attenuation Characteristic(NAC-16-472)
The attenuation characteristic of EMI filters is affected by
the input and output impedances of a measured circuit.
This attenuation characteristic (static characteristic) ismeasured under the constant condition of input andoutput impedances of 50 regardless of measurement
frequencies. This enables the attenuation characteristics
of different filters to be compared under the same
conditions.
However, actual electronic devices have different power line
impedances, and impedance itself has its own frequency
characteristic and does not take a constant value.
For these reasons, the attenuation characteristics (static
characteristics) that are specified in the catalogs for EMI
filters do not necessarily coincide with those when they
are attached to actual electronic devices.
One must also be careful that when connecting EMI filtersin series, the static characteristic of the resultant series is
not derived from simply adding the static characteristics[dB] of the individual filters.

11 Pulse Attenuation Characteristic
Bas-RhinEMI
Filter

Bas-Rhin

Figure 2.10.1 Attenuation Characteristic
Measurement Method(Single-phase Normal Mode)

Figure 2.11.2 represents how much the EMI filter can
attenuate pulse common mode noises, which may cause
malfunctions of electronic equipment, connected to a
power line. Figure 2.11.1 illustrates the measurement
method.
When terminating the input and output of the EMI filter
with 50 , and applying a specified pulse waveform on
the input, pulse voltages appearing on the output
are measured and plotted with the horizontal axis representing input pulse voltage and with the vertical axis
representing output pulse voltage.

Noise
Simulator

EMI
FilterEMI
FilterInput palace waveform

Figure 2.10.2 Attenuation Characteristic
Measurement Method(Single-phase Common Mode)

Technical Notes-8

July 21, 2022

Output pulse waveform

Figure 2.11.1 Measurement Method forPulse Attenuation Characteristic(Single Phase)2

Selection of EMI Filters[Pulse attenuation characteristic Pulse width: 1 µs]

0NAC-16-472(Ferrite core)

020

NAP-16-472(Amorphous core)

100

0

0.2

0.4

0.6

0.8
1.0
1.2
Input voltage [kV]

000

10

1.4

1.6

1.8

2.0

Attenuation [dB]

Output voltage [V]

200

221

30

471

40

102
50

222

EAP series
10A Rated article

60

Figure 2.11.2 Example of Comparing Pulse
Attenuation Characteristics

472

70

Figure 2.11.2 gives an example of comparing pulse
attenuation characteristics for an EMI filter using a general
ferrite core and one using an amorphous core.
The graph suggests that the amorphous core prevents
the voltage of output pulses from increasing quickly in
relation to rising input pulse voltage (a good pulse
attenuation characteristic).
Beyond a given volt-time product the choke coil of an
EMI filter will saturate, resulting in significantly reduced
noise suppression. The volt-time product (V.T) thatcauses the core to reach magnetic saturation is foundwith the following calculation expression:

According to the expresV : Pulse voltage [V]sion, an EMI filter using a
T : Pulse width [sec]core that has larger
B
B : Change of core’s magnetic(for example, an amorphous
flux density = Bm - Br [T]core) is less vulnerable
Bm: Saturation magnetic
to magnetic saturation,
flux density
assuming that the numbers
Br : Residual magneticof turns and the sizes offlux density
N : Number of turns in a coil [turns] cores are the same.
Ae: Effective cross section [m2]12 Ground Capacitor Codes

80
0.01

0.1

1
Frequency [MHz]

10

100

Figure 2.12.1 Example of Ground Capacitor Codes
and Common Attenuation Characteristics
Generally, the larger capacity one sets a ground capacitor
to, the better the common mode attenuation characteristic.
But, the leakage current will also become larger, whichmeans that there is a tradeoff.
The abundant selections of ground capacitor capacities
make it possible for one to develop the best balance
between attenuation characteristic and leakage current.

13 Options
Our EMI filters can be customized by specifying an
option code.
As the types of set options depend on filter products,
please refer to our catalog.
The following describes the outline of each option:a. DIN rail installation type: DThis type of EMI filter can be installed to a DIN rail
often used for control consoles, etc.

Many EMI filters can support various capacities ofground capacitors by specifying an appropriate code.
The selectable ground capacitor codes depend on thetypes of EMI filters; the following table lists an example
of ground capacitor codes and attenuation characteristics.
Table 2.12.1 Example of Ground Capacitor Codes (EAP series)
Code
000
101
221
331
471
681
102
222
332
472

Line to ground capacitor
Leak Current (input 125/250V 60Hz) (nominal value)
5 µA / 10 µA max
Not Provided
12.5 µA / 25 µA max
100pF
25 µA / 50 µA max
220pF
37.5 µA / 75 µA max
330pF
50 µA / 100 µA max
470pF
75.5 µA / 150 µA max
680pF
0.13 mA / 0.25 mA max
1000pF0.25 mA / 0.5 mA max
2200pF
0.38 mA / 0.75 mA max
3300pF
0.5 mA / 1.0 mA max
4700pF

Model Name
Rated Current

Figure 2.13.1 Examples of DIN Rail Installation
Type EMI Filters
Note that as this type of EMI filter may not produce
proper noise attenuation with grounding through a DIN
rail, one must connect the ground to the protective earthterminal (PE) of the EMI filter. For EMI filters that have
two protective earth terminals, it can connect the groundto either one only.

OptionGround Capacitor Codes

July 21, 2022

Technical Notes-9

2

Selection of EMI Filtersb. Terminal block type: T
These types of EMI filters use a terminal block as
their interface (if the standard product uses aconnector).

0[Option:T]

20

Attenuation [dB]

[Standard Product]e: With switch of line to ground capacitor type : G
These types of Ultra high attenuation type for EU,
With switch of line to ground capacitor.
Standard Product

40
60
80

100

Ultra high attenuation type for EU

120
0.1

1

Frequency [MHz]FTA -50 -683

0Standard Product

20
30
40

0

Option:H

20

60
70

0.01

0.1

1
Frequency [MHz]FTA -100 -104

10

100

Attenuation [dB]5080

FTA -50 -335

Figure 2.13.6 With switch of line to ground capacitor type
(Customers use when Test Voltage)f. Improve differential mode attenuation type : U
These types of change the rated voltage 250V.

Figure 2.13.3 Example of Comparing Common Mode
Attenuation Characteristics between
Standard Product and H-option Productd. Hexagon socket head cap bolt type: S
These types of EMI filters have a hexagon socket
head cap (Allen) bolt in their terminal block ininstead of the standard bolt (cross recessed(Philips) hexagon head bolt).
Customers can select the desired type of bolt fortools they are using.
[Standard Product][Option:S]

40
60

Standard Product80

Option:U

100

FTA -100 -104 -H

120
0.1

1

FTA -50 -683

Frequency [MHz]

10

100

FTA -50 -683-U

Figure 2.13.7 Example of Comparing differential Mode
Attenuation Characteristics between
Standard Product and U-option Productg. Ultra high attenuation type for EU : L
These types of Ultra high attenuation type for EU.
0
20

Attenuation [dB]

Attenuation [dB]

10

100

Figure 2.13.5 Example of Comparing Common Mode
Attenuation Characteristics between
Standard Product and Ultra high attenuation
type for EU ProductFigure 2.13.2 Comparison between
Standard Product and T-option Productc. High permeability choke coil type(ultra low-frequency and ultra high attenuation): H
These types of EMI filters the choke coil core witha high permeability core.
These types improve the common mode attenuation characteristic for low frequencies compared totheir standard products.

1040Standard Product

60
80

100
120
0.1

Option:L
1

Frequency [MHz]FTB-150 -663

10

100

FTB-150 -355-L

Figure 2.13.8 Example of Comparing Common Mode
Attenuation Characteristics between
Standard Product and L-option ProductFigure 2.13.4 Comparison between
Standard Product and S-option Producth. High input voltage : F
These types of change the rated voltage 500VAC/600VDC.
Option code is possible combination.
Please contact us for more information.

Technical Notes-10

July 21, 2022

3 How to Use EMI Filters
1 Ground Wiring
When wiring an EMI filter with a ground wire, use awire as thick and short as possible.
A long ground wire will deteriorate attenuation of highfrequencies due to inductance in the wire.

Long ground wire

100
90
80

Long ground wire

Short ground wire

Level [dBµV]

70
60
50
40
30
20

Short ground wire

10

Chassis ground0

Chassis ground
0.1

1

10

100

Frequency [MHz]Figure 3.1.1 Example of Ground wiring
Effed on Noise
Figure 3.1.2 Proper grounding

If customers connect the metal chassis of their EMI
filter, they can obtain an effect similar to a shortground wire.

2 Input and Output Wiring
Separate input wires from output wires.
If one binds input and output wires of EMI filters, orlays them close to each other, the filters may lose theirproper attenuation effect because the high-frequency
noise component may bypass them.
Twisting input (and / or output) wires in pairs can
redvce noise.

Input and output wires bundled(small distance between wires)

LINE

Motor
driverEMI
FilterBreaker

LOAD
100
90

Input and output wires bundled(small distance between wires)80

Level [dBµV]

70

Breaker

60
50

LINE

40
30
20

Input and output wires
kept separate

Input and output wires kept separate

EMI
Filter
LOAD

10
0
0.1

1

10

100

Frequency [MHz]Figure 3.2.1 Example of Effect ofwiring on Noise

Motor
driverFigure 3.2.2 Input and output wires

July 21, 2022

Technical Notes-11

4 Noise Reduction
1 Input and Output Impedance and Filter Circuit
The input/output impedances of a noise source and a load will have various optimal filter circuits.
General EMI filters take a configuration of a low pass filter that combines L and C. If the expected attenuation effect can
not be obtained, impedances of noise source and load may be the reasons.

Table 4.1.1 Combinations of I/O Impedances and Optimal FiltersHigh

Zi: Input impedance(impedance of noise source)

Noise source

EMI
FilterZo: Output impedance(impedance of load)

Low

Input impedance (Zi)

Output impedance (Zo)
High
Low

Figure 4.1.1 Input/output Impedances of an EMI Filter Circuit

2 EMI Filter Installation and Orientation
Generally, an EMI filter is placed in a way that the LINE terminal is connected to the input side, but it can also be used ina reverse configuration.
However, it may end up producing a different attenuation effect.
100

Connection

EMI
FilterMotordriver

90

Motor

80

M

70
Level [dBµV]

LINE LOAD

TAC-30Connection

EMI
FilterLOAD

MotordriverLINE

Connection

60
50
40
30

Motor

20

M

10
0

TAC-30Connection

0.1

1

10

100

Frequency [MHz]Figure 4.2.1 Direction in which an EMI Filter Is Attached and Connected

Figure 4.2.2 Example of Effed of Filter Orientation on Noise

If the internal circuit consists of a symmetric EMI filter (one of the NBC series or TBC series), the direction in which thefilter is connected will not cause any difference in noise attenuation. But in the case of asymmetric ones, it may cause
difference in the attenuation.
Case

Case
LINE

LOAD

LINE

LOAD

1

4

1

4

2

5

2

5

3

6

3

6

CY
CY

Figure 4.2.3 TAC Series Circuit Diagram(Circuit Is Asymmetric)

CY
CY

Figure 4.2.4 TBC Series Circuit Diagram(Circuit Is Symmetric)
CY: Line to ground capacitor: Mounting Plate

Technical Notes-12

July 21, 2022

4 Noise Reduction
100

3 Combining Multiple EMI Filters

90

Connection

EMI
FilterMotordriverLINE LOAD

Motor

80
70
Level [dBµV]

If one EMI filter cannot provide sufficient attenuation, the attenuation effect can be improved by connecting two filters in series.
However, one must pay attention to the fact that it will result in
combining the leakage current and voltage drop of two EMI filters.

10 Two set Connection
0EMI
FilterEMI
FilterLINE LOAD

LINE LOAD

TAC-30

TAC-30Motordriver

Motor

0.1

1

Frequency [MHz]

10

100

Figure 4.3.2 Example of Effect of Combining
Multiple Filters

M
0
10

EMI
FilterLOAD LINE

LOAD LINE

Motor
driver

20

Motor

30

M

40

TAC-30EMI
FilterEMI
FilterLINE LOAD

LOAD LINE

TAC-30

TAC-30MotordriverMotor

M

Attenuation [dB]EMI
Filter
TAC-30Connection

40

20

60
70

120
0.01

1
Frequency [MHz]

10

100

100
90
80
70
60

Connection

50
40

Connection

30
20

Connection

10
0

0.1

1

Frequency [MHz]

10

100

Figure 4.3.4 Comparing Effects of Different
2-filter Configurations

Motordriver

Motor

M

TAC-30100
90

The LINE side core insertion

80
70
Level [dBµV]

If one EMI filter cannot provide sufficient attenuation, the effect canbe improved by inserting an external core.
Whether a core is inserted on the LINE side or on the LOAD side ofan EMI filter may cause difference in the attenuation characteristic.
Core

0.1

Figure 4.3.3 Comparing Static Characteristics ofDifferent 2-filter cofigurations

4 External Ferrite Core

LINE LOAD

Connection

110

When connecting two EMI filters, the direction in which they areconnected may also cause difference in the attenuation characteristic.
Figure 4.3.3 shows the results of comparing the attenuation
characteristics (static characteristics) due to different directions inwhich two EMI filters are connected.
Figure 4.3.4 shows the actual sample noise characteristics caused by
the connection directions.
Unlike the static characteristic data, connection does not improve
the attenuation in this case. This phenomenon occurred because theinput and output impedances of the EMI filters were different from theconditions of static characteristics.
When trying to optimize the way EMI filters are connected, one mustevaluate by checking actual noise levels.

EMI
FilterConnection

80

100

Figure 4.3.1 Example of EMI Filter Connection Directions

Core

Connection

50

90

Level [dBµV]

Connection

One set Connection

50

30

M

TAC-30Connection

60

With no core

60
50
40
30

Figure 4.4.1 Example of Placing an External Core

20

When adding a core on the LINE side, one needs a core that cangenerate sufficiently large inductance for the choke coil within the EMI
filter.
Just inserting on the LINE side a core whose performance is equal toor less than that of the internal choke coil does not contribute to
reducing noise.
When inserting it on the LOAD side, it will produce a large attenuation
effect because the circuit takes a configuration of a T-type EMI filter circuit.

100

The LOAD side core insertion
0.1

1

Frequency [MHz]

10

100

Figure 4.4.2 Example of Effect of Adding an External
Ferrite Core

July 21, 2022

Technical Notes-13

5 EMC Test
1 CE Marking

3 Radiated Emission

For machines and electric products to be sold in the EU
area, manufacturers are required to bear a CE mark toprove they are in compliance with safety requirements,
quality control, and ecocide prevention. To be allowed to
do so, they must meet appropriate EC directives.
The following describes the EC directives that are
applied to general machinery products:

When operating equipment, the strength of electromagnetic
waves is measured in a range of specified frequencies at alocation 3 or 10 m away from the equipment

EN61000-6-4

Antenna
Turntable

3[m] or 10[m]a. Machinery directive

EUT

This directive covers products that are an assembly ofparts and have a driving section(with the central focus on industrial equipment).

1 - 4[m]0.8[m]

b. EMC directive
This directive is intended to apply to electric parts
which can be sources of radio disturbance or are
affected by electromagnetic interference. It requiresthat two items, emission (EMI) and immunity (EMS),
be met.

Figure 5.3.1 Example of Radiated Emission
Measurement Configuration

4 Power Supply Harmonic Current EN61000-3-2

c. Low voltage directive
This directive is intended to apply to products that
operate with a rated voltage in the range of 50 to1000 V AC or 75 to 1500 V DC.

One analyzes the frequencies of input currents andchecks the value of the harmonic current for each order.

As there are no appropriate EC directives (including
the ones described above) which apply to EMI filters,
EMI filter products cannot bear a CE mark.

5 Electrostatic Discharge EN61000-4-2

However, EMI filters can obtain an ENEC mark, which
has a similar effect on bypassing application proceduresof its signatories.

This test simulates effects of electrostatic discharge(malfunctions or destruction of semiconductor elements)
and includes contact discharge and aerial discharge inits scope.
Ipeak

2 Conducted Emission

100%
90%

EN61000-6-4

The voltages of interfering waves propagated through a
power cable from equipment to the outside aremeasured with LISN in an open site or anechoic
chamber .

at30ns
at60ns10%0.4[m]

0.8[m]

t

30ns
60ns
tr=0.7 to 1ns

EUT

Figure 5.5.1 Discharge current waveform

0.8[m]LISN

Table 5.5.1 Application Level
PowersupplyLevelFirst peak
Current value Current value
Specified discharge current
at 30 ns
at 60 ns
voltage
Rise time

Figure 5.2.1 Example of Conducted Emissions
Measurement Configuration

1

2kV

7.5A

0.7 - 1ns

4A

2A

2

4kV

15A

0.7 - 1ns

8A

4A

: Refer to the description in “Terminology related to EMC
Test” in this document.

3

6kV

22.5A

0.7 - 1ns

12A

6A

4

8kV

30A

0.7 - 1ns

16A

8A

Technical Notes-14

July 21, 2022

5 EMC Test
6 Radio frequency electromagnetic field EN61000-4-3

11 Voltage Dip/Momentary Power Interruption EN61000-4-11

This test checks immunities of equipment to effects ofelectromagnetic waves.

These tests check if equipment functions normally after
momentary voltage drop, or power failure that decreases
voltage to 0.
U

7 Fast Transient/Burst

EN61000-4-4This test checks immunities to burst waves by frominjecting via cable pulses that resemble the results of adischarge.

0

5

25

t
(Duration)

Figure 5.11.1 Example of a Waveform of Voltage Dips

8 Surge

12 Unit of NoiseEN61000-4-5This test checks immunities to surges by applying a
specified surge waveform.

U
1.0
0.9

20Log10

0.5
0.3
0.0

10 [V]
100 [V]
1000 [V]

T2
A

T
T1

max30%

1
1 × 10 -6

120 [dBµV]

140 [dBµV]
160 [dBµV]
180 [dBµV]

t

13 Detection Method

Figure 5.8.1 Example of a Surge Waveform in Voltage

a. Peak detection (PK)

Table 5.8.1 Level
Level
1
2
3
4
X

Noise is represented with 1 [µV] as its reference in [dB].
It is assumed that 1 [µV] equals 0 [dBµV].
For example, 1 [V] is represented as follows:

It detects the heights of peaks of an output waveform.

Open circuit test voltage±10% [kV]
0.5
1.0
2.0
4.0
specialb. Quasi-peak detection (QP)
It detects quasi-peaks through a circuit that has time
constants at the time of charge and discharge.
Quasi-peak detection value equals an intermediate
value between peak and average ones.
This detection has high measurement results whennoise has a long duration or occurs frequently.

9 Conducted Radio-frequency Interference EN61000-4-6
This test checks immunities to conducted disturbances
when electromagnetic waves pass into equipment
through a cable.

c. Average detection (AV)It detects an average of values of an output waveform.
Peak detection (PK)
Quasi-peak detection (QP)

10 Power Frequency Magnetic Field EN61000-4-8

Average detection (AV)This test checks immunities to magnetic fields generated by power frequency currents flowing through an
input line or a power wiring.

Figure 5.13.1 Relations between Detection Methods
and Measurement Levels

July 21, 2022

Technical Notes-15

5 EMC Test
14 Conducted and Radiated Emission Limits (Excerpt)
EN61000-6-3

Standard

EN55011

EN55022

EN60601-1-2

EN50370-1

Standard for
product groups

Standard for product groups

Standard for
product groups

ISM equipment

ISM equipment(medical equipment)

Machine tool−−Group 1
Common Common
standard standard Standard for product groups

Classification

Test item

EN61000-6-4

Product−

Operating environment

Information processing
equipment
20 kVA Exceeding (ITE equipment)−

Class BClass Aor less

Class B

20 kVAClass AClass B Class A Class B

20 kVA Exceeding 16A Exceedingor less 20 kVA or less 16AClass AClass A

QP
Limit

Conducted emission

Level:Unit [dBµV]

AV

0.1 - 50.5MHz

66 - 5679

66 - 5679

100

66 - 5679

66 - 56

79

100

79

100

0.5 - 5MHz

56

73

56

73

86

56

73

56

73

86

73

86

5 - 30MHz

60

73

60

73

90 - 73

60

73

60

73

90 - 7360

90 - 700.15 - 0.5MHz

56 - 4666

56 - 4666

90

56 - 4666

56 - 46

66

90

66

90

0.5 - 5MHz

46

60

46

60

76

46

60

46

60

76

60

76

5 - 30MHz

50

60

50

60

80 - 60

50

60

50

60

80 - 60

60

80 - 60

10m
Law
Limit

Radiated emission

Level:Unit [dBµV/m]

30m
Law

30 - 230MHz

30

40

30

40

50

30

40

30

40

50

40

50

230MHz - 1GHz

37

47

37

47

50

37

47

37

47

50

47

50

30 - 230MHz

−

30

−

−

−

−

−

−

−

−

−

−

230MHz - 1GHz

−

37

−

−

−

−

−

−

−

−

−

−

: Refer to the description in “Terminology related to EMC Test” in this document.

100

70

90

60

80
70

Level [dBµV/m]

Level [dBµV](As of November 2011)

60
50
40
30

50
40
30
20

20

10

10
0
0.1

1

Frequency [MHz]

10

100

100
Frequency [MHz]EN55011 ClassA QP (Group 1)

ClassB

EN55011 ClassA AV (Group 1)

ClassA

EN55011 ClassB QP (Group 1)
EN55011 ClassB AV (Group 1)(the above is also applied to EN55013, EN55014-1, EN55022, and EN60601-1)

Figure 5.14.1 Conducted Emission Limit Graph

Technical Notes-16010July 21, 2022

1000

Figure 5.14.2 Radiated Emission Limit Graph

5 EMC Test

6 Supplement

15 Terminology related to EMC Test

1 Source Voltages in the World

EUT
Stands for Equipment Under Test, and refers to equipmentthat will be tested or provided for a test.

People's Republicof China

Single phase 2 wire
220V

Three phase 4 wire 380V

TaiwanSingle phase 2 wire
110V, 220V

Three phase 4 wire 380V

India

Single phase 2 wire
230V, 240V

Three phase 4 wire
400V, 415V

Indonesia

Single phase 2 wire
220V

Three phase 4 wire 380V

Japan

Single phase 2 wire
100V, 200V

Three phase 3 wire 200V

Korea

Single phase 2 wire
110V, 220V

Three phase 3 wire 200V
Three phase 4 wire 380V

Philippines

Single phase 2 wire
220V, 230V, 240V

Three phase 3 wire 480V

SingaporeSingle phase 2 wire
230V

Three phase 4 wire 400V

ThailandSingle phase 2 wire
220V

Three phase 4 wire 380V

Malaysia

Single phase 2 wire
240V

Three phase 4 wire 415V

Egypt

Single phase 2 wire
220V

Three phase 4 wire 380V

Saudi Arabia

Single phase 2 wire
127V, 220V

Three phase 4 wire 380V

Australia

Single phase 2 wire
240V

Three phase 4 wire 415V

New ZealandSingle phase 2 wire
230V, 240V

Three phase 4 wire
400V, 415V

Austria

Single phase 2 wire
230V

Three phase 4 wire 400V

FranceSingle phase 2 wire
230V

Three phase 4 wire 400V

Germany

Single phase 2 wire
230V

Three phase 4 wire 400V

UK

Single phase 2 wire
240V

Three phase 4 wire 415V

Netherlands

Single phase 2 wire
230V

Three phase 4 wire 400V

Italy

Single phase 2 wire
220V

Three phase 4 wire 380V

Spain

Single phase 2 wire
127V, 220V

Three phase 4 wire 380V

Switzerland

Single phase 2 wire
230V

Three phase 4 wire 400V

Single phase 2 wire
127V, 220V

Three phase 4 wire 380V

USA

Single phase 2 wire
120V, 265V, 277V
Single phase 3 wire
115/230V, 120/240V,
240/480V

Three phase 4 wire
208V, 460V, 480V

BrazilSingle phase 2 wire
127V

Three phase 4 wire 220V

Immunity test
Refers to a test to evaluate the durability of EUT
against electromagnetic interference.

Emission test
Refers to a test to evaluate whether the strength ofelectromagnetic interference emitted from EUT exceeds agiven limit.

Open site
Refers to an experimental facility installed outdoors to
be used for activities such as EMC measurement.

Anechoic chamber
Refers to a facility to be used to create an electromagneticallyisolated environment; the interior surfaces of the chamberabsorb radio frequency waves.

CISPR
One of IEC’s special committees; it was established tointegrate standards such as those for allowable values andmeasurement methods for interfering waves causing radio
communication failures and includes a standardizationcommittee for EMC (Electro Magnetic Compatibility).

Group 1 and Group 2 in EN55011
Group1 : Equipment for laboratories, healthcare, and sciences(Example: frequency counters, spectrum analyzers,
switching power source, and measuring apparatus)
Group2 : Industrial induction heating equipment, induction
heating equipment,
industrial microwave heating equipment, household
microwave ovens,
medical equipment, spark erosion equipment, andspot welders.

ISM equipment
Stands for Industrial, Scientific and Medical radio-frequency
equipment and refers to radio-frequency equipment forindustry, science, and health care.

LISN
Stands for Line Impedance Stabilization Network. It refers toequipment that sends noise components to a measurement
device while monitoring impedances, looking at the powersource from EUT. It is also called AMN (Artificial Mains
Network).

Russia(former republicsof the Soviet Union)

OR D EM PR
O

OR

ES

SO

July 21, 2022

Technical Notes-17