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http://catalog.moeller.net

Author: Dipl.-Ing.Wolfgang Esser

Energy-saving interface contactors enable the precisetechnological andeconomic interactionof electromechanicaland electronic switch-gear. The integrationof electronic compo-nents in the newlydeveloped magnetdrive system of thexStart contactorsis the basis for theirexceptionally highperformance.xStart interface contactors now optimally switch electrical equipmentup to 15 kW witha device width ofjust 45 mm. All of Moeller's standard DC contactors up to15 KW are interfacecontactors.

Special Print

Skilful Combination of Technological Advantages

The conventional methodology usedwith automation technology entails func-tion levels. There are optimally imple-mented with electromechanical and elec-tronic switchgear. Particular significanceis attached to the technical precision andeconomic implementation of the inter-faces between the functional levels of the “signal processing”, using electronicautomation systems and the “signal out-put” via the contactors. Important userbenefits are to be found in the optimi-sation of these interfaces.

FFiigguurree 11 indicates the function levelsand the interfaces which enable com-munication between the levels. The indi-vidual functional levels can vary greatlydepending on the tasks and the extent ofthe electrical systems, and in straightfor-ward cases, can extend to simple andsmall control panels which engage eachother.

Contactors, amplifiers betweenlogic processing and equipment

The different conventional actuatingvoltages, frequencies and the varyingapplications (AC and DC are required)make alternating current and direct cur-rent magnetic systems necessary for reli-able movement of the contact mecha-nisms. Contactors are manufactured invast quantities for operation with alter-nating control voltages. However, theuse of contactors with DC current mag-netic systems are preferred for use toge-ther with electronic systems. Based on theextremely positive experiences with the

contactors for large and very large powers, the new contactor frame sizesabove 12 A also received DC-operatedmagnetic drives whose power is electro-nically matched to the respective switch-ing state. This solution is already a proventechnological highlight at Moeller and

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Energietechnik

Skilful Combination of TechnologicalAdvantagesHybrid Interface Contactors Switch Equipment up to 15 kW

The technical description describes the properties of energy-savinginterface contactors and implements their improved features asbenefits for the user. Interface contactors enable the precisetechnological and economic interaction of electromechanical andelectronic switchgear. The integration of electronic components inthe newly developed magnet drive system of the xStart contactors is the basis for their exceptionally high performance.xStart interface contactors now optimally switch electrical equip-ment up to 15 kW with a device width of just 45 mm. All of Moeller's standard DC contactors up to 15 KW are interfacecontactors.

Wolfgang Esser

Dipl.-Ing. Wolfgang Esser (57) is manager productsupport

industrial switch gears businessunit circuit breaker and motor

starter at Moeller GmbH, Bonn. E-Mail: wolfgang.esser@

moeller.net

Figure 1: Functional levels and interfaces of an automation system

Power distribution

Pow

e su

pply

Input

Processing

Output

Pow

er s

ection

• Machine• System• Process

Actuators

Sensors

Man/Machine Dialog

Figure 2: Opened contactor for powers up to 15 kW / 400 V, with the enclosure base, thelaminated iron core, the magnetic coil with the attached electronic circuit board and theenclosure top with armature and the integrated contacts.

features identical dimensions for AC andDC operated contactors. Resource-savingAC current magnetic systems are nowused for both types of voltage. Table 1compares the most significant differencesbetween conventional alternating voltageand direct voltage magnetic systems. Inaddition, the special features of the newelectronically-supported xStart magneticdrive is shown (Figure 2).

The magnet system is the centrepiece ofthe contactors. Its careful dimensioningsignificantly influences

• the mechanical and electrical contactlifespan,

• a reliable level of contact reliability, • the maximum permissible contact use, • the permissible mounting position,• the safe operating range of the actua-

ting voltage,• the effective compatibility with elec-

tronic systems and • finally, the energy balance of the con-

tactor as well as the entire switchgearsystem.

Electronic components with digital semiconductor outputs forDC voltages

Electronic systems and componentscan feature different output-side designs.With automation systems such as pro-grammable logic controllers (PLC), digi-tal semiconductor outputs for DC voltageare most prevalent. Typical for these ty-pes of output is that the output voltage issimultaneously the actuating voltage forthe contactor or a coupling relay. An out-put voltage of 24 V DC is generally

3• Heft 12/2004

Principle differences between AC and DC operated magnet systems

Feature Conventional AC operated contactor

Conventional DC operated contactor

Modern DC operated magnetsystem with electronic supportfrom Moeller

Coil current Is determined by: Frequency, resistance and induc-tance of the coil

Is determined by: Resistive load of the coil

Is determined by: Conversion toreduced holding voltage, (approx.0.1 x Un), resulting in extremely reduced holding power• Very low heat loss• No lateral clearance required

between the contactors

Power consumption Pick-up power is significantly higherthan holding power, inductance ismuch less during switch on than inthe “on” position due to large polesurface clearance

Pick-up power = holding power, meaning that the holding power ishigh with uninterrupted operation

Holding power is extremely low,pick-up power approximately thesame as with conventional DC-actuation

Power of the magnet system is proportional to the square of the coilcurrent

Force alternating between 0 andFmax with a frequency of 2 x f(i)

Proportional to current rise Proportional to current rise

Makes short-circuit ring necessaryso that force > 0 with stroke = 0 mm

Force is always > 0, as the currentis always > 0

Force is always > 0, as the current is always > 0

Current control from pick-up to holdby change of the inductance (polesurface clearance)

Constant current through constantresistance

A time controlled switchover between a pick-up and holding current circuit as it were

Magnet system structure Simple Complicated and larger than an ACoperated system

Dimension of the AC and DC magnet system are identical

Iron core Laminated Solid Laminated

Noise development Humming is possible in holding mode

No hum No hum

Additional functions Optional, external suppressor Usually an external suppressor Generally integrated suppressor(function such as bridge rectifierand fast de-energization)• Prevents dangerous voltage

peaks during shutdown

Protection against polarity reversalusing a diode (device does notswitch on!)• Protects electronics when incor-

rectly connected

Table 1: The table indicates the most important difference between conventional AC and DC magnet systems and the new DC magnetsystems with electronic support

selected. The output loadability of the se-miconductors used differs but is usually0.5 A with today''s systems.

DC semiconductor outputs offer the ad-vantage that they are very affordable andpermit a high packing density in controlsystems. Usually, multiple outputs arecompiled to an output module. These out-puts will not be all simultaneously andpermanently loaded with full rated cur-rent with conventional contactors. Up tonow, a utilization factor had to be frequently considered when engineeringsystems.

“Output level to the powersection” interface

The devices for high-power switchingand protection of the equipment are located in the power section of theswitchgear system. High currents flowhere which switch voltages that are up to690 V. The term “equipment” representsmotors, but can also represent valves asinterfaces to the pneumatics, hydraulics,supply lines or dosing and metering units.Resistive loads such as heating or in some cases lighting represent electricalequipment. With motors, the higher cur-rents must be switched as 3-phase cur-rents. Contactors are required for thispurpose.

Three main possibilities for implemen-tation are available on the interface bet-ween the electronic output of the logicprocessing and the contactor:• indirect actuation with separate, spati-

ally separated coupling elements,• indirect actuation with adapted or inte-

grated coupling elements• and the particularly effective direct

actuation of interface contactors.With the indirect actuation, a coupling

relay for power matching and also formatching the voltage level and voltagetype is used between the electronic out-put and contactors. Compared to separate,spatially separated coupling elements,the space requirement for contactors withintegrated coupling element is less, theclarity is better and the wiring effort is reduced (e.g. with Moeller contactors >500 A).

With direct actuation the output of theelectronic components are connected directly to the coils of the contactors. Thevoltage of the electronic output and con-tactor coil are identical. If contactorswith low power magnet drive systems(Figure 3) are used, this is the connectiontype with the most efficient use of space,mounting and wiring effort and with thelowest propensity for faults.

New DC operated contactors,powerful electronic partners

The most important construction ele-ments of the contactors are the magnetsystem and the contact mechanism. Elec-trical switch-on commands are convertedto forces in the magnet system, whichmove the contact bridge and cause thecontacts to close and remain closed. Con-tactors normally have a monostable switching behaviour. It opens automati-cally when the switch on command is nolonger present. This behaviour is neces-sary for example, to ensure that a motordoes not restart after a malfunction in thesupply of power. Conform to the IEC / EN60 204-1, Safety of machinery – Electri-cal equipment of machines, it may onlyrestart after a new and intentional switchon command is issued.

The contactor contacts can switch alternating current, three-phase current orDC current loads. Contactors are intendedfor relatively fast and frequently actuatedloads that are either switched remotely orfrom an automation system. Interfacecontactors are new at Moeller for the 12– 32 A current range. The interface con-tactors are characterised by their low power consumption and a wide actuationvoltage tolerance range. The interfacecontactors for 17, 25 or 32 A avail of thesame contact mechanisms as the AC oper-ated contactors manufactured in largequantities. Contact form and size, silvercontent and switching distance are iden-tical. The contacts of the interface con-tactors offer the same high level of con-tact reliability. The differences which

enhance the effectiveness are due to thenew magnet system. The magnet systemis now electronically supported (Figure 4)so that the power consumption of themagnet system is matched to the respec-tive force requirement of the contacts.The force requirement is higher when clo-sing the contacts than in the closed state.The switch-on dynamics are improved bythe force adjustment, which becomes evident by an increase in the lifespan ofthe contact as contact bounce is reducedvery significantly by the elimination ofexcessive energy. The magnet systemelectronics ensure a constant voltage onthe magnet system independently of de-viations in the actuating voltage. A con-stant magnetic flux is achieved on themagnet system. Constant switching speedsare thus achieved which also significant-ly enhance the lifespan of the contacts.

A further technical and economic benefit of the new magnet system resultsfrom the general integration of a “fast”suppressor. This suppressor reduces thevoltage induced current peaks of the

drive coils to an acceptable and non-dan-gerous level without causing unaccepta-ble switch off delays. This eliminates theneed for the user to select, purchase andinstall an external suppressor. Throughthe use of a suppressor it is also permis-sible to engineer mechanical contactsbetween electronic outputs and contactorcoils, for example with safety interlocks.

The switch-on voltage tolerance of the

4 Heft 12/2004 •

Figure 3: The electronic-compatible newcontactors with DC interface drives from theMoeller xStart system feature a holdingpower of just 0.5 W and a particularly widevoltage range. Motor starters up to 15 kWonly require a width of 45 mm.

Figure 4: An electronic matching of thedrive forces to the switching sequencereduces power consumption. It ensures adefined voltage threshold for uniform voltageconditions in a wide voltage range. Ultima-tely, it was possible due to the electronics tointegrate an auxiliary contact on a width ofjust 45 mm and to move the coil connectionto the front side for simplified wiring.

Energietechnik

5• Heft 12/2004

Energietechnik

interface contactors extends beyond thedemands of the IEC / EN 60947-4-1 [1] orthe harmonised DIN VDE 0660 standard.The admissible range for safe switch on isbetween 0.7 – 1.2 x Ue. The holding power of the contactors for AC-3 currentsup to 32 A or 15 kW powers at 400 V isonly 0.5 W. Of particular significance inconjunction with electronic controls isthe 24 V DC actuating voltage, as this isthe conventional output voltage on theirsemiconductor outputs. The voltage limitsfor electronic controls are defined in theIEC 61131-2 [2] standard. The interfacecontactor coils have been dimensionedespecially for these wide voltage toleran-ces. Furthermore, several voltage coilranges are available which can be fullyused for the larger voltage tolerances. Ac-cording to Figure 5, the safe operatingrange with regard to the voltage rangeexample between 200 and 240 V, is bet-ween 140 and 288 V.

The large voltage tolerances of the DCmagnetic drives also help with all appli-cations, where a higher voltage drop oc-curs due to the cable lengths. With alter-nating voltages, the cable capacitance'sof longer cables can lead to a voltagedrop. In the worst case, an AC contactorat the end of a long cable will not longerde-energize. DC operated contactorsshould be used preferentially here, as de-layed de-energization of the contactordrive is avoided. Even if the DC-actuatingvoltages are taken from a rechargeablebattery, the wide voltage tolerances areuseful as excess voltages occur during therecharging process.

The new DILM interface contactorsfrom Moeller can now switch with anAC-3 switching duty of up to 15 kW /400 V more than 80 % of all three-phasemotors which are used. The contactorscan now be connected directly withoutfurther components with the digital semi-conductor outputs for DC voltage. Withutilization category AC-1, three-phasecurrents up 80 A or single-phase currentseven up to 400 A can be switched. Thesevalues are particularly interesting for domestic automation applications andfor machines and systems for the gene-ration of electric heat. The larger newcontactors for AC-3 powers up to 75 kWalso have similar magnetic drives, whosehigher power consumption's also are verysignificantly less than conventional con-tactors. These contactors are up to 25 %narrower than their predecessors.

User benefits of interfacecontactors on DC semiconductoroutputs

On output modules where a utilizationfactor had to be observed up to now, theengineering is less of a problem, as thepower consumption of the contactor coil is too small and the critical total load of the output assembly can no longerbe achieved.

The voltage drop on the semiconductoroutputs is for physical reasons and rela-tively high. The load current (coil currentof the contactor) inevitably generates heat losses, which when above the prede-fined limit values impair the reliabilityand lifespan of the output module. This

danger no longer exists with xStart inter-face contactors. Even if an electronic sys-tem has high power outputs, it is morefavourable for the entire electronic sys-tem when the load current is kept as lowas possible and the outputs remain “cold”as a result.

Due to the low coil currents on manycontactors, the heat balance of the entirecontrol panel is more favourable. Controlpanel fans are no longer required in some cases. The sum of the coil currentsmust be supplied by the power supplyunits. The customer benefits of low powerconsumption contactors is also due to thefrequently smaller and more attractivelypriced dimensioning of these power sup-ply modules. The interface contactor inquestion enables a space saving and ex-ceptionally cost-effective fulfilment ofthe latest American market demands fromthe semiconductor industry (SEMI F47[4]), as the bridging of voltage dips with-out add-on modules demanded in thestandard can be achieved.

The contactors belong to the newxStart motor starter system from Moeller.The system also covers – in addition tocontactor relays and contactors – motor-protective circuit-breakers and overloadrelays up to 150 A. Significant advant-ages of the new system result from thesignificant reduction in the number ofvariants and through the dimensional reduction of many components. All mo-tor starters up to 15 kW / 400 V are nowimplemented on a width of just 45 mm. Auxiliary contacts are already imple-mented in this width. New busbar adap-ters and a comprehensive range of elec-trical spacers are on offer for fast andspace saving mounting. But even abovethis system up to 150 A, the very largeMoeller DIL M contactors and DIL Hcontactors up to 2000 A offer an excel-lent electronic compatibility by electroni-cally supported drives.

Literature:[1] IEC / EN 60 947-4-1 and DIN VDE 0660-102

“Low-voltage switchgear and controlgear –

Part 4-1: Contactors and motor-starters; Elec-

tromechanical contactors and motor-starters”

[2] IEC / DIN EN 61 131-2, VDE 0411 part 500

“Programmable controllers - Part 2: Equipment

requirements and tests”

[3] SEMI F47-0999

“Provisional Specification for Semiconductor

Processing Equipment SAG Immunity”

Figure 5: Voltage tolerance of the DIL M17 to DIL M150 DC actuated contactors incomparison with the stipulations of the IEC / EN 60947-4-1 [1] standard. The enhancedundervoltage and overvoltage tolerance provides a significant contribution to reliability andfault-proofing of electrical switchgear, which is combined with electronic controls.

140 V 170 V 200 V 240 V 264 V 288 V

70 % 85 % 100 % 100 % 110 % 120 %

Plus Norm PlusNormRated voltage ofthe contactor coil

Think future. Switch to green.

Moeller addresses worldwide:www.moeller.net/addressE-Mail: info@moeller.net

© 2004 by Moeller GmbHSubject to alterationsVER2100-946GB MDS/ETZ 12/04Printed in the Federal Republic of Germany (12/04)Article No.: 289992

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