SYSTEM Electronics ETC-QUAD UL - Power Supply Sizing

page 17
January 2020 - Rev. 1.2
Order Cod. 1902503003
9.3 Terminal board removal
ThefrontpaneloftheMicrostep unitisttedwiththe
I/Oterminalboard.The panelandthus allthewiring
is easily removable from the unit by simultaneously
leveragingonthetwotabsattheendsofthecontainer.
Themaneuverinvolvestheejectionofthefront.
The front is closed by placing the same in its seat
(keepingthetabsopen)andthenclosingthetabsuntil
itclicksintoplace(Figure9.3.1).
Figure 9.3.1 Terminal board removal
9.4 EtherCAT bus wiring
TheEtherCATwiringenablesreal-timecommunication
withthesupervisorandtheadjacentEtherCATnodes.
Use shielded cables that meet the minimum requirements
forcategory5,classDofstandardIEC11801.
ItisrecommendedtouseCat5categoryandshielded
4-wirecables.
TheEtherCATcableshieldallowstoattenuateelectrical
interferences in an industrial environment that might
corruptcommunication.
Donotinstallthecommunicationcablewiththemotor
powercablesorinparallelwiththem,butputthemin
separate cable ducts.
Donotextendthecommunicationcableswithadapters
or extension cables, but use a cable of appropriate
length.Onrequestshieldedcablesandadapterstobe
installedintheeldcanbesupplied.
The EtherCAT cable is connected to the earth of the
ETC-QUADdrivethroughdecouplingcapacitors,asper
EtherCATspecications,toavoidacompensatingcurrent
owingontheshieldoftheconnectingcable.
10. Power supply
sizing
Inorder to sizethe power supplyproperly, one must
carefully assess several factors, such as: the motor
used,thenumberofsimultaneousaxesonewantsto
movesimultaneously,themotorspeedandcurrent,the
brakingtorqueandthemomentoftheload.
Thesectionoftheconductorsandthedistancefromthe
powersourceaectinturnthepowersizing.
Thesupply voltageaects the maximumacceleration
atwhichitispossibletomovethemotor:accordingto
theinductanceofthemotorwinding,infact,thecurrent
takestimeto reachsteady stateconditions, givenby
the formula V = L dI/dt . (where I is the maximum
current applied, typically the boost current starting
fromstandstill).
Onemustmaintainasafetymargintopreventexceeding
180Vinanyoperatingcondition.Itisrecommendednot
toexceed150Vdcofnominalpower.
Itisrecommendedtouseapowersupplythatprovides
arectiedvoltagewitharipplebelow1Vpp:thepower
supplyripplehasanegativeimpactonthetorque.
Thepowersupplymustbecapableofdeliveringpowerto
themotorsthataregoingtooperatesimultaneously:the
RMScurrentat150Vdcpersingleaxiscanbeestimated
approximatelyequalto3Awithtypicalmotorsandspeed
prolesforsteppermotors.
Whenamotorisdecelerated,inthepresenceofaload
withahighmomentofinertia,thekineticenergyofthe
system is converted to electrical drive power, raising
thesupplyvoltage.Thepowersupplymustensurethat
themaximumvoltagedoesnotreachdangerouslevels,
consideringallthemotors thatcould moveovertime
andthatcouldbestoppedatthesametime:onemust
in fact also consider the possible emergency stops in
whichseveralaxesmustbestoppedassoonaspossible.
Theenergythatcannotbeusedbyothermotorsthat
moveisstoredinthecapacitors,ifproperlysizedeven
followingbrakingtests.
If the capacitors are not sufficient to accumulate
the energy input to the power bus, there should be
an active or passive circuit for limiting the transient
overvoltage.
Testsandyearsofexperienceintheuseofsteppermotors
recommendusingatleast2'500uFcapacitors(min250V)
pereachaxiswhichmaymovesimultaneously,uptoa
maximumof25'000uFpermachine,tolimitthestart-up
currentandthestressonthepowerdiodes.
E.g.:foramachineinwhichonecanmoveupto4axes
simultaneously,includea250V10'000uFcapacitor.
The power Bus remains at a dangerous voltage
after switching the machine o. Wait for the
power bus to reach a voltage below 40V before
intervening or remove the terminal board.
Attention!
Risk of Electric Shock, wait 1 minute before operating.
Attention!
Risque de choc électrique, attendez 1 minute avant
d'utiliser.
It is recommended to include a power bus discharge
system.
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