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

EPCOS AG 2017. Reproduction, publication and dissemination of this publication, enclosures hereto and the

information contained therein without EPCOS’ prior express consent is prohibited.

EPCOS AG is a TDK Group Company.

Ferrites and accessories

Toroids (ring cores)
General information and overview

Date:

May 2017

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Cautions and warnings

and

Important notes

at the end of this document.

Toroids (ring cores)

General information

Our product line includes a wide range of toroids with finely graded diameters ranging from 2.5 to
202 mm.
Other core heights can be supplied on request. All cores are available in the usual materials.

Applications

■

Toroids are primarily used as EMC chokes for suppressing RF interference in the MHZ region
and in signal transformers.
Typical applications for toroids of NiZn ferrites are LAN chokes. One of the materials available
for this purpose is K10; other materials on request.

The following high-permeability MnZn materials are available for interference suppression:

– R 2.5 through R 12.5 for telecommunications (N30, T38, T46)
– R 13.3 through R 26 for power line chokes (N30, T65, T35, T37, T38)
– >R 34 for chokes and filters in industrial use (T65)

■

Toroids are also increasingly used for power applications. Here, the typical values for amplitude
permeability and power loss, as summarized in the section on “

SIFERRIT Materials

” (page 36),

are applicable to the special power materials.

Coating

Toroids are available in different coating versions, thus offering the appropriate solution for every
application. The coating not only offers protection for the edges but also provides an insulation func-
tion.
For small ring cores, we have introduced a parylene coating which features a low coating thickness
and high dielectric strength.
A coating of the core will cause μ

to drop, depending on the core size. A similar effect might occur

when the core is subjected to high winding forces, especially cores made of the high permeability
materials, T38 and T46.

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Coatings of ring cores

Dielectric strength test

The following test setup is used to test the dielectric strength of the insulating coating: A copper ring
is pressed to the top edge of the ring. It touches the ferrite ring at the edges (see diagram).
The test duration is 2 seconds.

Version

Epoxy
(blue)

Parylene
(transparent)

Main application

Medium/big sizes
(

≥

R 9.53)

Small sizes
(<R 9.53)

Layer thickness

<0.4 mm

0.012 or 0.025 mm

Breakdown voltage
(minimum values)

>1.0 kV (for R 9.53; R 10)
>1.5 kV (for R 12.5 thru R 20)
>2.0 kV (for >R 20)

>1 kV
(standard value)

Mechanical quality

High firmness

Smooth surface

Maximum temperature
(short-time)

approx. 180

approx. 130

Maximum temperature
(long-time)

approx. 130

Advantage

Low influence on A

value

Very low thickness

UL rating

UL 94 V-0

UL file number

E194412/E257941

E194412

Ordering code

B64290

…

B64290

…

Ferrite ring

Metal poles

rms

General information

Toroids (ring cores)

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Chamfer

Large toroidal cores use thick wires that are partially subjected to high mechanical stress during
winding. This can damage the wire insulation as well as the coating of the cores, thus reducing the
breakdown voltage. To avoid this, EPCOS toroids have a chamfer. This prevents any insulation
damage, and produces uniform coating thickness at the same time.

Cutting

Middle size and large toroids are available with gap:

1.) Cut into 2 halves with typical cuting wheel

2.) Cut gap in required thickness.

thickness 1.2 mm.

Three basic questions have to be answered during order:
– toroid cuts into 2 halves/only gap (picture 1 or 2)
– cutting before/after coating

– before: air gap is coated
– after: air gap is not coated, a measurement fixture can be placed into the air gap

– required thickness of the gap

FUS0127-3

Core size

Design

Small

Edges rounded by tumbling

Medium

Chamfer on edges and/or radius on the surface

Medium/big

Chamfer on edges

General information

Toroids (ring cores)

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Structure of the ordering code (part number)

General information

Toroids (ring cores)

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Toroids (ring cores)

B64290

Overview of available sizes

Type

Type code
(ordering code,
block 2)

Page
(Data
book)

Toroid size (d

inch

R 2.50

1.50

1.00

R 0.098

0.059

0.039

P0035

624

R 2.50

1.50

1.30

R 0.098

0.059

0.051

P0072

624

R 2.54

1.27

R 0.100

0.050

P0734

625

R 3.05

1.27

R 0.120

0.050

P0683

625

R 3.05

1.27

2.54

R 0.120

0.050

0.100

P0739

626

R 3.05

1.78

2.03

R 0.120

0.070

0.080

P0733

626

R 3.43

1.78

R 0.135

0.070

P0731

627

R 3.43

1.78

2.03

R 0.135

0.070

0.080

P0745

627

R 3.94

1.78

R 0.155

0.070

P0732

628

R 3.94

2.24

1.30

R 0.155

0.088

0.051

P0061

628

R 3.94

2.24

2.30

R 0.155

0.088

0.090

P0723

629

R 4.00

2.40

1.60

R 0.157

0.094

0.063

P0036

629

R 4.00

2.40

1.80

R 0.157

0.094

0.071

P0692

630

R 5.84

3.05

1.52

R 0.230

0.120

0.060

P0056

630

R 5.84

3.05

3.00

R 0.230

0.120

0.118

P0687

631

R 6.30

3.80

2.50

R 0.248

0.150

0.098

P0037

631

R 8.00

4.00

R 0.315

0.158

P0751

632

R 9.53

4.75

3.17

R 0.375

0.187

0.125

L0062

632

R 10.0

6.00

4.00

R 0.394

0.236

0.157

L0038

633

R 10.0

6.00

7.00

R 0.394

0.236

0.318

L0783

633

R 12.5

7.50

5.00

R 0.492

0.295

0.197

L0044

634

R 12.7

7.90

6.35

R 0.500

0.311

0.250

L0742

634

R 13.3

8.30

5.00

R 0.524

0.327

0.197

L0644

635

R 14.0

9.00

5.00

R 0.551

0.354

0.197

L0658

635

R 15.0

10.4

5.30

R 0.591

0.409

0.209

L0623

636

R 15.8

8.90

4.70

R 0.622

0.350

0.185

L0743

636

R 16.0

9.60

6.30

R 0.630

0.378

0.248

L0045

637

Overview

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Overview of available sizes

(continued)

Type

Type code
(ordering code,
block 2)

Page
(Data
book)

Toroid size (d

inch

R 17.0

10.7

6.80

R 0.669

0.421

0.268

L0652

638

R 18.4

5.90

R 0.724

0.232

L0697

638

R 20.0

10.0

7.00

R 0.787

0.394

0.276

L0632

639

R 20.0

10.0

R 0.787

0.394

L0631

639

R 20.0

10.0

15.0

R 0.787

0.394

0.591

L0710

640

R 22.1

13.7

6.35

R 0.870

0.539

0.250

L0638

640

R 22.1

13.7

7.90

R 0.870

0.539

0.311

L0719

641

R 22.1

13.7

12.5

R 0.870

0.539

0.492

L0651

641

R 22.6

14.7

9.20

R 0.890

0.579

0.362

L0626

642

R 25.3

14.8

10.0

R 0.996

0.583

0.394

L0618

642

R 25.3

14.8

15.0

R 0.996

0.583

0.590

L0615

643

R 25.3

14.8

20.0

R 0.996

0.583

0.787

L0616

643

R 29.5

19.0

14.9

R 1.142

0.748

0.587

L0647

644

R 30.5

20.0

12.5

R 1.201

0.787

0.492

L0657

644

R 34.0

20.5

10.0

R 1.339

0.807

0.394

L0058

645

R 34.0

20.5

12.5

R 1.339

0.807

0.492

L0048

645

R 36.0

23.0

15.0

R 1.417

0.906

0.591

L0674

646

R 38.1

19.05

12.7

R 1.500

0.750

0.500

L0668

646

R 40.0

24.0

16.0

R 1.575

0.945

0.630

L0659

647

R 41.8

26.2

12.5

R 1.646

1.031

0.492

L0022

647

R 50.0

30.0

20.0

R 1.969

1.181

0.787

L0082

648

R 58.3

32.0

18.0

R 2.295

1.260

0.709

L0043

649

R 58.3

40.8

17.6

R 2.295

1.606

0.693

L0040

650

R 58.3

40.8

20.2

R 2.295

1.606

0.795

L0042

651

R 63.0

38.0

25.0

R 2.480

1.496

0.984

L0699

652

R 68.0

48.0

13.0

R 2.677

1.890

0.512

L0696

653

R 87.0

54.3

13.5

R 3.425

2.138

0.531

L0730

654

R 102

65.8

15.0

R 4.016

2.591

0.591

L0084

655

B64290

Toroids (ring cores)

Overview

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Toroids (ring cores)

R 140

103

25.0

R 5.512

4.055

0.984

A0705

656

R 202

153

25.0

R 7.953

6.024

0.984

A0711

657

Type

Type code
(ordering code,
block 2)

Page
(Data
book)

Toroid size (d

inch

Overview

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Mechanical stress and mounting

Ferrite cores have to meet mechanical requirements during assembling and for a growing number
of applications. Since ferrites are ceramic materials one has to be aware of the special behavior
under mechanical load.

As valid for any ceramic material, ferrite cores are brittle and sensitive to any shock, fast tempera-
ture changing or tensile load. Especially high cooling rates under ultrasonic cleaning and high static
or cyclic loads can cause cracks or failure of the ferrite cores.

For detailed information see data book, chapter

“General - Definitions, 8.1”

Effects of core combination on A

value

Stresses in the core affect not only the mechanical but also the magnetic properties. It is apparent
that the initial permeability is dependent on the stress state of the core. The higher the stresses are
in the core, the lower is the value for the initial permeability. Thus the embedding medium should
have the greatest possible elasticity.

For detailed information see data book, chapter

“General - Definitions, 8.1”

Heating up

Ferrites can run hot during operation at higher flux densities and higher frequencies.

NiZn-materials

The magnetic properties of NiZn-materials can change irreversible in high magnetic fields.

Ferrite Accessories

EPCOS ferrite accessories have been designed and evaluated only in combination with EPCOS
ferrite cores. EPCOS explicitly points out that EPCOS ferrite accessories or EPCOS ferrite cores
may not be compatible with those of other manufacturers. Any such combination requires prior te-
sting by the customer and will be at the customer‘s own risk.

EPCOS assumes no warranty or reliability for the combination of EPCOS ferrite accessories with
cores and other accessories from any other manufacturer.

Processing remarks

The start of the winding process should be soft. Else the flanges may be destroyed.

– Too strong winding forces may blast the flanges or squeeze the tube that the cores can not be

mounted any more.

– Too long soldering time at high temperature (>300 °C) may effect coplanarity or pin arrange-

ment.

– Not following the processing notes for soldering of the J-leg terminals may cause solderability

problems at the transformer because of pollution with Sn oxyde of the tin bath or burned insula-
tion of the wire. For detailed information see chapter

“Processing notes”

, section 2.2.

– The dimensions of the hole arrangement have fixed values and should be understood as

a recommendation for drilling the printed circuit board. For dimensioning the pins, the group
of holes can only be seen under certain conditions, as they fit into the given hole arrangement.
To avoid problems when mounting the transformer, the manufacturing tolerances for positioning
the customers’ drilling process must be considered by increasing the hole diameter.

Cautions and warnings

Ferrites and accessories

Cautions and warnings

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Cautions and warnings

and

Important notes

at the end of this document.

Ferrites and accessories

Display of ordering codes for EPCOS products

The ordering code for one and the same product can be represented differently in data sheets,
data books, other publications and the website of EPCOS, or in order-related documents such as
shipping notes, order confirmations and product labels.

The varying representations of the

ordering codes are due to different processes employed and do not affect the
specifications of the respective products

. Detailed information can be found on the Internet

under www.epcos.com/orderingcodes.

Cautions and warnings

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Important notes

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Symbol

Meaning

Unit

A
A

min

Bˆ

CDF
DF
d
E

f
f

cutoff

max

min

g
H
Hˆ
H

h
h/

I
I

Iˆ
J
k
k

Cross section of coil
Effective magnetic cross section
Inductance factor; A

= L/N

Minimum inductance at defined high saturation (

)

Minimum core cross section
Winding cross section
Resistance factor; A

= R

RMS value of magnetic flux density
Flux density deviation
Peak value of magnetic flux density
Peak value of flux density deviation
DC magnetic flux density
Remanent flux density
Saturation magnetization
Winding capacitance
Core distortion factor
Relative disaccommodation coefficient DF = d/

Disaccommodation coefficient
Activation energy
Frequency
Cut-off frequency
Upper frequency limit
Lower frequency limit
Resonance frequency
Copper filling factor
Air gap
RMS value of magnetic field strength
Peak value of magnetic field strength
DC field strength
Coercive field strength
Hysteresis coefficient of material
Relative hysteresis coefficient
RMS value of current
Direct current
Peak value of current
Polarization
Boltzmann constant
Third harmonic distortion
Circuit third harmonic distortion
Inductance

nH
nH
mm

μΩ

= 10

–6

Vs/m

, mT

Vs/m

, mT

Vs/m

, mT

Vs/m

, mT

Vs/m

, mT

Vs/m

, mT

Vs/m

, mT

F = As/V
mm

–4.5

J
s

–1

, Hz

–1

, Hz

–1

, Hz

–1

, Hz

–1

, Hz

mm
A/m
A/m
A/m
A/m
10

–6

cm/A

–6

cm/A

A
A
A
Vs/m

J/K

H = Vs/A

Symbols and terms

Ferrites and accessories

Symbols and terms

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Symbol

Meaning

Unit

L/L

rev

N
P

trans

PF
Q
R
R

s
T

t
t

tan

U
Û
V

Z
Z

Relative inductance change
Inductance of coil without core
Main inductance
Parallel inductance
Reversible inductance
Series inductance
Effective magnetic path length
Average length of turn
Number of turns
Copper (winding) losses
Transferrable power
Relative core losses
Performance factor
Quality factor (Q =

L/R

= 1/tan

)

Resistance
Copper (winding) resistance (f = 0)
Hysteresis loss resistance of a core
R

change

Internal resistance
Parallel loss resistance of a core
Series loss resistance of a core
Thermal resistance
Effective loss resistance of a core
Total air gap
Temperature
Temperature difference
Curie temperature
Time
Pulse duty factor
Loss factor
Loss factor of coil
(Residual) loss factor at H

→

Relative loss factor
Hysteresis loss factor
Relative loss factor of material at H

→

RMS value of voltage
Peak value of voltage
Effective magnetic volume
Complex impedance
Normalized impedance |Z|

= |Z| /N

)

H
H
H
H
H
H
mm
mm

W
W
mW/g

Ω
Ω
Ω
Ω
Ω
Ω
Ω

K/W

mm
°C
K
°C
s

V
V
mm

Ω
Ω

/mm

Symbols and terms

Ferrites and accessories

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Important notes

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All dimensions are given in mm.

Surface-mount device

Symbol

Meaning

Unit

α
α

Φ
η
η

μ
μ

app

rev

tot

ρ
Σ

l/A

Temperature coefficient (TK)
Relative temperature coefficient of material
Temperature coefficient of effective permeability
Relative permittivity
Magnetic flux
Efficiency of a transformer
Hysteresis material constant
Hysteresis core constant
Magnetostriction at saturation magnetization
Relative complex permeability
Magnetic field constant
Relative amplitude permeability
Relative apparent permeability
Relative effective permeability
Relative initial permeability
Relative real (inductive) component of

(for parallel components)

Relative imaginary (loss) component of

(for parallel components)

Relative permeability
Relative reversible permeability
Relative real (inductive) component of

(for series components)

Relative imaginary (loss) component of

(for series components)

Relative total permeability
derived from the static magnetization curve
Resistivity
Magnetic form factor
DC time constant

= L/R

= A

Angular frequency;

= 2

1/K
1/K
1/K

-1

–1

–1/2

Vs/Am

–1

s
s

–1

Symbols and terms

Ferrites and accessories

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Cautions and warnings

and

Important notes

at the end of this document.

The following applies to all products named in this publication:

1. Some parts of this publication contain

statements about the suitability of our products for

certain areas of application

. These statements are based on our knowledge of typical require-

ments that are often placed on our products in the areas of application concerned. We never-
theless expressly point out

that such statements cannot be regarded as binding statements

about the suitability of our products for a particular customer application.

As a rule, EP-

COS is either unfamiliar with individual customer applications or less familiar with them than the
customers themselves. For these reasons, it is always ultimately incumbent on the customer to
check and decide whether an EPCOS product with the properties described in the product spec-
ification is suitable for use in a particular customer application.

2. We also point out that

in individual cases, a malfunction of electronic components or fail-

ure before the end of their usual service life cannot be completely ruled out in the current
state of the art, even if they are operated as specified.

In customer applications requiring a

very high level of operational safety and especially in customer applications in which the mal-
function or failure of an electronic component could endanger human life or health (e.g. in acci-
dent prevention or life-saving systems), it must therefore be ensured by means of suitable de-
sign of the customer application or other action taken by the customer (e.g. installation of pro-
tective circuitry or redundancy) that no injury or damage is sustained by third parties in the event
of malfunction or failure of an electronic component.

The warnings, cautions and product-specific notes must be observed

4. In order to satisfy certain technical requirements,

some of the products described in this pub-

lication may contain substances subject to restrictions in certain jurisdictions (e.g. be-
cause they are classed as hazardous)

. Useful information on this will be found in our Material

Data Sheets on the Internet (www.epcos.com/material). Should you have any more detailed
questions, please contact our sales offices.

5. We constantly strive to improve our products. Consequently,

the products described in this

publication may change from time to time

. The same is true of the corresponding product

specifications. Please check therefore to what extent product descriptions and specifications
contained in this publication are still applicable before or when you place an order.

We also

reserve the right to discontinue production and delivery of products

. Consequent-

ly, we cannot guarantee that all products named in this publication will always be available. The
aforementioned does not apply in the case of individual agreements deviating from the foregoing
for customer-specific products.

6. Unless otherwise agreed in individual contracts,

all orders are subject to the current version

of the “General Terms of Delivery for Products and Services in the Electrical Industry”
published by the German Electrical and Electronics Industry Association

(ZVEI)

7. The trade names EPCOS, CeraCharge, CeraDiode, CeraLink, CeraPad, CeraPlas, CSMP,

CTVS, DeltaCap, DigiSiMic, ExoCore, FilterCap, FormFit, LeaXield, MiniBlue, MiniCell, MKD,
MKK,  MotorCap,  PCC,  PhaseCap,  PhaseCube,  PhaseMod,  PhiCap,  PowerHap,  PQSine,
PQvar,  SIFERRIT,  SIFI,  SIKOREL,  SilverCap,  SIMDAD,  SiMic,  SIMID,  SineFormer,  SIOV,
ThermoFuse,  WindCap  are

trademarks registered or pending

in Europe and in other

countries. Further information will be found on the Internet at www.epcos.com/trademarks.

Important notes