Buck–BoostTransformers
Buck-Boosttransformersaresmall,singlephase,drytype distributiontransformersdesignedandshippedas insulating/isolatingtransformers.Theyhaveadualvoltage primaryandadualvoltagesecondary.Thesetransformerscanbeconnected forawiderange ofvoltagecombinations.Themostcommonuseistobuck(lower)orboost (raise)
thesupplyvoltageasmallamount,usually5to27%. Buck-boosttransformersareincompliancewithNEC Article210.9, Exception1whenfieldconnected as
anautotransformer.
Themajoradvantages ofBuck-boosttransformersaretheir lowcost, compactsizeandlightweight.Theyarealsomoreefficientandcost lessthanequivalentisolationtransformers. Whenconnectedasanautotransformer,theycanhandleloadsupto20 timesthenameplaterating.Abuck-boost transformer istheidealsolutionforchanging linevoltageby smallamounts.
Whenabuck-boosthastheprimaryandsecondarywindings connected,perrecommendedinstructions,itbecomesan autotransformer.Now,onlythesecondarywindingsare transformingvoltageandcurrent.ThemajorityofthekVA
loadpassesdirectlyfromthesupplytotheload.Thisisthe
reasonbuck-boosttransformerscansupplyaloadwitha muchlargerkVAratingthanthenameplateindicates.
Lowvoltagelightingcontrolapplications
SolaHDbuck-boosttransformersaredesignedtosupply powertolow voltagelightingcircuits,controlpanels or othersystemsrequiring12, 16, 24, 32, or48 Volts.When connectedasaninsulatingtransformer(byfollowingthe wiringdiagramlocated afterthespecificationtables onthe insideofthetransformer case), thetransformer’scapacity matchesthenameplatekVArating.
SolaHDbuck-boosttransformersarealsosuitedforlowvoltagelandscape lighting.TheyareULListedforoutdoor serviceandtheircompact sizemakes themtheperfect solutionforprovidingpowertoaccentlightingapplications. ElectricalConnectiondiagramsareshownattheendof
thissection.
Usedimmersontheoutput ofthetransformerthataredesignedandratedforusewithmagneticloads.Westronglyrecommendcontactingthedimmermanufacturerforadvice onyourspecificlightingapplication.
CertificationsandCompliances
•Listed
-UL506
-CSAC22.2No.66
Accessories
•SurgeProtective Devices
•ActiveTracking®Filters
Threephase,buck-boostapplicationsrequiretwoorthree transformers.Checkthe“QuantityRequired”columnoftheThreePhaseSelectionTablesfortheexactquantity.
FusingBuck-BoostTransformers
Fordeterminingthecorrectsizeofbreaker orfuseforagiven
rangeofinputoroutputampereratings,refertoSection
450.4, oftheNationalElectricCode (NEC).
Whereanovercurrentprotection deviceisrequired,the electricalconnectionsandselectiontableswillreference appropriately.
UsingtheSelectionTables
1. DetermineifyouaretryingtoBoost(raise)orBuck (lower)yourvoltage.Selectaninput/outputvoltagecombinationthatcomesclosesttomatchingyour applicationfromtheappropriatesingleorthreephasechartsonthefollowingpages.
2. Moveacross yourselectedinput/outputvoltagerowto theamperageorkVAratingclosestto,butgreaterthan theratingrequiredbyyourload.
3. Readingthetopofthecolumnwillgiveyouthe catalognumberoftheexactbuck-boosttransformer youneed. SeetheSpecificationTablesonthe
nextpage.
4.Connectthetransformersaccordingtothediagramindicated.SeetheElectricalConnectionssectionatthe endofthissection.Connectiondiagramsarepackedwitheachtransformer.
Selection Steps
1.InputLineVoltage
Measure thesupplyvoltagewithavoltmeter.
2.VoltageRequiredfortheLoad
Checktheloadequipmenttodetermine thevoltage
requirement.
3.kVAorAmpereRatingoftheLoad
FindeithertheloadkVAortheloadamperage requirements.Thisinformationislistedonthenameplateoftheloadequipment.
4.Frequency
Either50 or60 Hz.The frequencyofthetransformer mustmatchthefrequencyoftheload.
5.NumberofPhases
Singleorthreephaselineandloadmustmatch.
(Atransformercannotconvertsingletothreephase.)A common applicationistomakeasinglephaseconnectionfromathreephasesupplybyusingonephaseofthethreephasesupplycircuit.Becarefulnot tooverloadthatphaseofthethreephasesupply.For buck-boostapplications thesupplymustprovideload kVA–notjustthenameplateratingofthebuck-boost.RefertotheSelectionTablesonthefollowingpages.