EMC-compatible - Induteq...Conductive arrangement of mains filters on gland plates or mounting...

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Rittal practical assembly tips

EMC-compatibleenclosure assembly

The definition of electromag-netic compatibility (EMC) isthe ability of an electricaldevice to function satisfacto-rily in its electromagneticenvironment without adver-sely affecting this environ-ment, which may includeother equipment.

On the basis of this, theessential requirements ofEMC are: To prevent/reduceinterference emission andto offer defined resistanceagainst interference.

EMC is an indispensable ele-ment of quality, and the pro-tection requirements regu-lated by law, along with thetechnical risks, EMC must betaken into account at theplanning stage when devel-oping equipment.

With the enclosure, as ahousing for electrical/elec-tronic controls and systems,the following points must beobserved:

– These days, the intelli-gence contained insideenclosures is becomingever faster, i.e. shorterswitching times and steeper pulse edges, leading to ever higher frequencies of voltagesand currents.

– Ever lower energy con-sumption, i.e. lower vol-tage/current levels,means that componentsare more readily influ-enced by interference.

– The siting of controls in ever more confinedspaces, i.e. smallerdistances between components and cables,causing ever more fre-quent interference on different paths.

– Technical progress willexacerbate these riskseven further.

A standard enclosure madeof coated sheet steel canmake a significant contribu-tion towards the EMC ofcontrols for machinery andsystems, provided somesimple population rules aretaken into account.

In applications with high-frequency field-boundinterference, the use of anRF-shielded enclosure witha superior shielding effectmay be required. The onlyway to draw definite con-clusions about the type ofenclosure which is neces-sary or adequate to complywith certain standard limitsis by conducting measure-ments.

This brochure is intended toprovide recommendationsfor EMC-compatible enclo-sure assembly and usage inmachinery and systems fordaily workshop practice.

The Rittal EMC concept

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Paint

SZ 2415.000

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Comprehensive potential equalisation

Measures within the enclosure

Cabling rules

This section contains valuable tips andinformation on comprehensive potentialequalisation.

This section contains practical sug-gestions for EMC measures within theenclosure.

This section tells you the points youshould take into account with cabling.

Explanation of symbols The following symbols have been used inthis manual for illustrative purposes.

We have also assigned system accessoriesto the drawings, to make ordering easier.

very good good very poor

very sensitive sensitive

poor

Effectivenessof the EMCmeasures

Immunityto inter-ference

Strippaint

Paint surfacewith contactpaint

high low

Inter-ferenceemission

Enclosure forpower distribution

Enclosure forcontrol andmeasurementtechnology

Steel reinforce-ment in concreteceilings, metallic basesin false ceilings

Earth connections

5m

Duct forpower cable

Duct forlow-powercable

4


For EMC purposes, ideally there should be low andhigh-frequency potential equalisation between all metalicmasses, enclosures, machine and system compo-nents, which should be meshed as closely as possible.

Measuringdevice

Enclosure

Machine

1

1

2

1 Power supply2 Data/control connection

Measuringdevice

Enclosure

Machine

1

1 2

Enclosure 1

Cable

Cable

Earth connection2Enclosure

Reference potential

Enclosure 1

Cable

Reference potential

2Enclosure

Loop

5


Basic principle: Avoid large cable loops; lay current-carrying cables as close as possible to the referencepotential.

Cable routing in machinery and equipment

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L

B

Potentialequalisationrail

EarthingstrapsSZ 2412.210 –SZ 2412.325

In practice: Maximumpossible cross section,large-area conductivemounting, low-inductive(therefore, a rectangleis better than a roundconductor)

Green-and-yellowPE conductor

Ideally:LB

< 3

Potential equalisationconnections

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Paint

SZ 2415.000

Paint

SZ 2415.000

Plain washerand spring lockwasher

Screw connection

Springlockwasher

Screw connection

How to attach earthing straps

How to screw-fix metallic parts

Preparationof the contact points Contact cutter

for frame sectionSZ 2414.000

Contact cutterfor earthing boltsSZ 2414.500

Potential equalisationconnections

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Green-and-yellowconductor

Potential equalisation between enclosures via a metallic cable duct

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1 Conductive connection2 Contact paint provides protection against corrosion

1

2Paint

SZ 2415.000

How to connect metallic cable ducts to the enclosure

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Paint

SZ 2415.000

Paint

SZ 2415.000

Conductive connectionof metallic cable ducts

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Comprehensive potential equalisationConductive connection of metallic cable ducts

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Conductive attachment of metallic cable ducts

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Welded earthing strap

Conductive connection between machine and system components

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High outputs Low outputs

Input Low outputs High outputs

Functional enclosure layout / spatial division

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High outputs Low outputs

Div

idin

g ar

ea

More powerfulcomponents

Mains Actuators Transducers, probes,detectors

Protect sensitive assembliesby means of encapsulation,shielded case/subrack withinthe enclosure

Functional enclosure layout, division via internal partitions

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Enclosure within an enclosure

Potential equalisationvia suitable rails orconductive mounting plate

Air-conditioning apertureswith RF filters

Mains filter/overvoltageprotection at the point of entry,with large-area contact

Unshielded control cablesvia filter openings conductivelyconnected to the enclosureentry point

Conductive sealbetween the enclosure andremovable enclosure panels

Shielded viewing window,as small as possible

Shielded cables via EMC PGscrewed cable glands

For optimum shielding effect:

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EMC earthing straps

Earth strapsSZ 2412.210 –SZ 2412.325

SZ 2412.210 –SZ 2412.325

Improve the shielding effect via optimum potential equalisationof the enclosure surfaces

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Painted sheet metal

Long

PE

con

duct

or

Conductive mounting plate

The mounting plate as a potential equalisationsurface: all components with a conductive housing can be conductively mounted with alarge contact area.

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Potential equalisationon the mounting plateSZ 2367.060 -SZ 2367.120

Ideally: All-round contact

EMC shield busSZ 2413.375 andSZ 2367.060 - SZ 2367.120

EMC gland platesPS 4314.060 -PS 4314.080

EMC cable glandsSZ 2411.090 -SZ 2411.360

Solderedring terminal

Tin-platedbraiding

Cable shields should be contacteddirectly at the point of cable entry, where possible

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Power supply

Output:To actuator or to machine

Paint =insulation

SZ 2367.060-SZ 2367.120

Filter

Power supply

Output:To actuatoror tomachine

FilterPowersupply

Output: To actuatoror to machine

Filter

CA

CA =controlassembly

CA

CA

Important: Spatially separate inputand output cables from one another;use as shielded cables

Conductive arrangement of mainsfilters on gland plates or mounting plate,cable shield contacting ongland plates or mounting plate

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Paint =insulation

Power supply

Filter

Important: Ensure there islarge-area conductive connectionbetween the filter housing andthe mounting surface;avoid cable loops to the referencepotential

Paint

SZ 2415.000

Filter

Power supply

Filter

Position filters directly at the point of enclosure entry/exit, where possible

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Metallic earth

Position transformers on gland plateswith large-area conduction, conductive connection of the shield

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Cabling rules

Multi-wire cable,shielded,in metal tube

or in metalliccable duct

Multi-wire cable

Unused conductor

Shielded,twistedcable pair

Shielded, twistedcable pair withextra shielding

Imm

unit

y to

inte

rfer

ence

Unshielded,twisted cable pair

Multi-wire cable,unshielded

Multi-wire cable,shielded

Inte

rfer

ence

emis

sio

n

Cable selection/routing

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Cabling rules

C cable tube,surface-mounted

Surfacecablingwith cableclamps orother fixingcomponents

Sheathings,open layingof bus cablesetc.

Steel conduit

Steelcable duct

Cable traysor sheetsteel supports

Cable routing between enclosures and machine/system parts

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Cabling rules

Open metallic cable duct Open mounting angle

Areas with effective shieldingagainst electromagnetic fields

Plasticcable duct

Solidmetallic cable duct

Routing of cables in the cable ductSelection/population of cable ducts

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Cabling rules

Unshielded cable

D

Unshielded cable

Unshielded cable

Unshielded cable

Immunity tointerference

Interferenceemission

Very sensitive High

Sensitive Low

D as large as possible

How to route cables with different interference emission and interference sensitivity in cable ducts

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Cabling rules

= lambda: wavelengthof the maximum frequencyoccurring in the vicinity

Reference potential(machine chassisor separate rail)

L ≤ 10 m

L ≈10

m

Reference potential orpotential equalisation railwith connection to chassis

Cable shield withpotential equalisation on one side

Cable shield withoutpotential equalisation contact

Shield contacting to potential equalisation

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Cabling rules

Output

Control

Sig

nals

> 2

0 cm90

°90

°

Connect unused conductor to reference potential

Use right-angled cable cross-overs wherever possible, and ensure adequatedistance between interference-emitting and sensitive cables

< 2

0 cm

Cable routing

Fix it by fax:

Simply copy and complete this form, and fax it us !

From:

Surname First name

Company Department

Road

Town/post code

Telephone Fax

Request for information:

Please send me more information about:EMC subracksEMC instruments casesEMC wall-mounted enclosuresEMC enclosure systemsEMC fan-and-filter units

Please telephone me to arrange an appointment.My extension is:

Please send me …… additional copies of this brochure.

Reliable protection against interference

Play it safe with the Rittal EMC range.Sophisticated standard products for EMC-compatiblepackaging of electrics, electronics and data communica-tions provide reliable protection against electromagneticinterference. Rittal EMC solutions are available as:

• EMC subracks• EMC instrument cases• EMC wall mounted enclosures• EMC enclosure systems• EMC fan-and filter units• and a wide range of EMC accessories.

New! Ripac MicrocomputerPackaging System:The complete subrack solution with the com-prehensive EMC concept.

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Rittal-Werk � Rudolf Loh GmbH & Co. KG � P.O. Box 16 62 � D-35726 HerbornTelephone (0 27 72) 5 05-0 � Telefax (0 27 72) 5 05-23 19 eMail: [email protected] � Internet: http://www.rittal.com

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EMC-compatible - Induteq...Conductive arrangement of mains filters on gland plates or mounting...

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