Comparison of advantages and disadvantages between high-voltage motor and low-voltage motor

High-voltagemotorandlow-voltagemotorhavetheirownadvantagesanddisadvantages.Whataretheiradvantagesanddisadvantages?   Comparedwithlow-voltagemotor,high-voltagemotorhasthefollowingadvantages:   1.Thepowerofthemotorcanbeincreasedtoseveralthousand,eventensofthousandsofkilowatts.Thisisbecause,atthesamepoweroutput,thecurrentofthehigh-voltagemotorismuchsmallerthanthatofthelow-voltagemotor.Forexample,theratedcurrentof500KW,4-stagethree-phaseACmotorisabout900Awhenratedvoltageis380V,andonlyabout30Awhenratedvoltageis10KV.Therefore,thewindingofTakanomotorcanbeusedwithsmallerdiameter.Asaresult,thestatorcopperlossofthehigh-voltagemotorwillbesmallerthanthatofthelow-voltageclick.Forlargerpowermotors,whenusinglowvoltage,largerstatorslotsareneededbecauseofthickerconductors,whichmakesthediameterofstatorcoreverylargeandthevolumeofthewholemotorbecomeverylarge.   2.Forlarge-capacitymotors,thetotalinvestmentofpowersupplyanddistributionequipmentusedbyhigh-voltagemotorsislessthanthatoflow-voltagemotors,andthelinelossissmaller,whichcansaveacertainamountofpowerconsumption.Especiallythe10KVhighvoltagemotorcandirectlyusethepowergrid.Inthisway,theinvestmentinpowerequipmentwillbecomeless,theusewillbecomeeasier,andthefailureratewillbecomesmaller.   Comparedwithlow-voltagemotor,thedisadvantagesofhigh-voltagemotorareasfollows:   1.Thecostofwindingisrelativelyhigh,andthecostofrelatedinsulatingmaterialswillincreaseaccordingly.   2.Therequirementofusingenvironmentismuchhigherthanthatoflowvoltagemotor.   3.Theinsulationtreatmentprocessismoredifficult,theman-hourcostismore,andthemanufacturingcycleofthemotorislonger.

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Motor Efficiency in Ground Source Heat Pump System

HighEfficiencyMotorQuestion Accordingtotheworkingefficiencyofthemotor,therearetwokindsofmotorsusedingroundsourceheatpumpsystem:standardefficiencymotorandhighefficiencymotor.Comparedwithstandardefficiencymotors,theefficiencyofhighefficiencymotorscanbeincreasedby2to10percentagepointsaccordingtothedifferentpower.Highefficiencymotorsarerealizedbybetterdesignanduseofspecialmaterialsthatcanreducelosses,butthepriceisabout10%~30%higherthanstandardefficiencymotors,soonlyonefifthoftheMotorssoldworldwidearehighefficiencymotors.Motorefficiencyistheratioofmechanicalpoweroutputtopowerinput,usuallyexpressedasapercentage.Figure1showsthedifferencebetweenstandardmotorandhighefficiencymotor.Highefficiencymotorproducedbyimproveddesignmaterialsandtechnologycangeneratemorepowerperunitpowerconsumption. Usually,highefficiencymotorshavehighloadcoefficient,betterinsulationandvoltagewithstand,lowcalorificvalueandlessvibration,thusincreasingreliability.HighefficiencymotorsmusthaveafullloadefficiencyequaltoorgreaterthanthatofordinarymotorsspecifiedbytheAmericanAssociationofInternationalElectricalManufacturers(NEMA).Inotherwords,amotorefficiencymustbeequaltoorexceedtheNEMAhighefficiencymotorfullloadengineeringefficiencyvaluebeforeitcanbecalledahighefficiencymotor.Thecostofahigh-efficiencymotordependsontheprice,efficiency,usetime,installationandmaintenancecostsandlaborcostsofthemotor.Theextrapurchasecostofhigh-efficiencymotorscanbequicklyrecoveredbysavingoperatingcosts.Usually,theextracostofhigh-efficiencymotorscanbeoffsetbytheenergyconsumptionsavedbytwoyearsofoperation.Forexample,assumingthat50hp,75%oftheloadfactormotorrunsformorethan4,000hoursperyearandtheelectricitycostis$0.04/kWh,animprovementpointcansave4079kwhor$163peryear.Therefore,ahighefficiencymotor,through4%efficiencyimprovement,cansave$1304intwoyearscomparedwiththestandardmotor,basicallymeetthetwo-yearreturnstandard. TheRelationbetweenMotorSpeedandLoad Theloadofcentrifugalpumpsandfansisextremelysensitivetothechangeofspeed.Increasingthespeedbyonly5r/mincanleadtoasignificantincreaseinflowspeedandenergyconsumptionandadecreaseinefficiency.Therefore,whenreplacingapumporfan,thefullloadspeedmustbechosentobeequaltoorlowerthanthespeedofthereplacedmotor.Thepowerofthecentrifugalmotordrivingthefanisproportionaltothecubeoftherotationalspeed.Forexample,ifthespeedofthemotorincreasesfrom1740r/minto1760r/min,thepowerconsumptionwillincreaseby3.5%eventhoughitonlyincreasesby20r/min,andtheairorwatervolumewillchangewiththesquareofthespeed.Slipandspeeddependonload,whichmakesitpossiblefordifferentmotorstodrivethesameload.Forexample,whena100hpmotoroutputs25%ratedpower,itcanbereplacedbya50HPorlowerhorsepowermotor,butatthistimethepoweris50%of50hp,or62.5%of40hp,83%of30HPmotor,and25HPfullloadoutput.Whentheloadofthemotorincreasesgradually,thespeedwilldecrease,andthefull-loadspeedwillbethefull-loadspeed.Hence,theAnhuiElectricPowerMotorindicatesthatonlythemotorwithlowerspeedorlargerloadcanoperateinawayclosetothesynchronousspeed,andthatthemotorwithlowerpowerandfull-loadefficiencycanworkataspeedclosetothesynchronousspeedinsteadofthemotorwithhigherpowerbutlowerspeed,whichcanobviouslysaveoperation.Cost.

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