Samlexpower PST-1000-12 Owner's manual - Section 8 |
32 | SAMLEX AMERICA INC.
- Ac induction motors: Thesearecommonlyfoundinpowertools,appliances,well
pumpsetc.Theyexhibitveryhighsurgedemandswhenstarting.Significantvoltage
drop in these circuits may cause failure to start and possible motor damage.
- PV battery charging circuits: These are critical because voltage drop can cause a dis-
proportionatelossofchargecurrenttochargeabattery.Avoltagedropgreaterthan
5%canreducechargecurrenttothebatterybyamuchgreaterpercentage.
Fuse Protection in Battery circuits
Abatteryisanunlimitedsourceofcurrent.Undershortcircuitconditions,abatterycan
supplythousandsofAmperesofcurrent.Ifthereisashortcircuitalongthelengthof
thecablesthatconnectsthebatterytotheinverter,thousandsofAmperesofcurrent
can flow from the battery to the point of shorting and that section of the wire will be-
comered-hot,theinsulationwillmeltandthecablewillultimatelybreak.Thisinterrup-
tionofveryhighcurrentwillgenerateahazardous,hightemperature,high-energyarc
withaccompanyinghigh-pressurewavethatmaycausefire,damagenearbyobjectsand
cause injury. To prevent occurrence of hazardous conditions under short circuit condi-
tions,anappropriatefuseshouldbeusedinthebatterycircuitthatwilllimitthecur-
rent,blowinaveryshorttimeandquenchthearcinasafemanner.forthispurpose,UL
ClassTfuseorequivalentwithAmpereInterruptingCapacity(AIC)ofatleast10,000A
shouldbeused(AsperULStandard248-15).Thisspecialpurposecurrentlimiting,very
fastactingfusewillblowinlessthan8msundershortcircuitconditions.Appropriate
capacityoftheaboveClassTfuseshouldbeinstalledwithin7”/178mmofthebattery
Plus(+)Terminal.Thefusewillrequireacorrespondingfuseholder.
WARninG!
Useofanappropriatelysizedexternalfuseasdescribedaboveismandatoryto
provide safety against fire hazard due to accidental short circuit in the battery
wires.PleasenotethattheDCsidefuse(s)insidetheunitaredesignedtopro-
videprotectiontotheinternalcomponentsoftheinverter.ThesefuseswillNoT
blow if there is a short circuit along the length of wires connecting the battery
and the inverter.
Recommended Sizes of Wires and external Fuses
Thefollowingsizesofwiresandexternalfusesarerecommended.Thedistanceof3ft.
(.91metres)/6ft.(1.83metres)/10ft.(3.05metres)isthedistancebetweenthebattery
and the inverter. The running length of routing of the wire should be considered if the
wiring run is not straight but circuitous. The recommended size of wires will limit the
voltagedropto2%ofthenominalbatteryvoltage(0.24Vfor12Vbatteryand0.48Vfor
the24Vbattery)
Thelengthofthewireforcalculatingvoltagedrophasbeentakenas2timesthedis-
tance between the inverter and the battery assuming that 2 lengths of wires (one Posi-
tiveandoneNegative)areusedfortheconnection.DCresistancevaluesarebasedon
uncoated,strandedcopperconductorsatatemperatureof167°f/75°C.Thistempera-
ture is typical of operating power circuits.