Motorola GTR 8000 - DC Power Connection Wire Gauge Calculations for HPD; DC Power Connection Wire Gauge Calculations for Integrated Voice and Data; Table 3-3 DC Power Connection Wire Gauge Maximum Distances for Integrated Voice & Data

3.4.3.2DCPowerConnectionWireGaugeCalculationsforIntegratedV oiceandData
3.4.3.2DCPowerConnectionWireGaugeCalculationsfor
IntegratedVoiceandData
SincethepowersupplydisconnectsitselffromtheDCinputwhenitsensesthatDCvoltagehasdroppedto42VDC,
itisimportanttominimizethevoltagedropintheDCpowersupplyloop(thetotallengthofthe48VDChotwire
andtheDCreturnwire)tonomorethan1Vtotal.Thisensuresthatthemaximumenergyisremovedfromthe
batterypriortodisconnectingthepowersupplyfromtheDCinputline.
Abaseradiotransmittingat100Wwilldrawupto10A*currentwhenoperatingfroma54Vsource(nominal48
VDCsystem).Asvoltagedecreases(duetothestandbybatterydischarging)thecurrentwillincreaseproportionally
(sincethebaseradioappearstobeaconstantpowerload).Atthelowvoltagedisconnectpoint(42Vforanominal
48VDCsystem),thecurrentwillbeupto13A*.Ifasinglepairof2AWGwireisusedtoconnectthebatterytothe
backpanel,themaximumlengthofasingleconductorwouldbe75m(245ft).Useofsmallergaugewirewould
reducethislengthdependingontheresistanceofthewire.
*=Theactualcurrentvaluecanbecalculatedfromthepowerconsumptionvalueinthespecicationstables.See
1.9GTR8000BaseRadio/GPW8000ReceiverSpecications,page1-12.
Todeterminethemaximumlengthofwireforwireotherthan2AWG,thefollowingrelationshipcanbeused:
•Length(meter/feet)=V/I/R
where:
•V=voltagedropinonelegoftheloop(max=0.5V)
•I=currentdrawnbythebaseradioduringDCoperation
•R=resistanceofthewirebeingconsidered(inOhmsperfoot)
Forcommonwiresizes,themaximumdistancesshowninTable3-3apply.
Table3-3DCPowerConnectionWireGaugeMaximumDistancesforIntegratedVoice&Data
AWG
Resistance(ohm/304.8meter/
1000ft)
MaximumDistance(for13A)
20.1563
75m(245ft)
30.1970
60m(195ft)
40.2485
47m(155ft)
5
0.3133
37m(120ft)
60.3951
30m(95ft)
3.4.3.3DCPowerConnectionWireGaugeCalculationsforHPD
SincethepowersupplydisconnectsitselffromtheDCinputwhenitsensesthatDCvoltagehasdroppedto42VDC,
itisimportanttominimizethevoltagedropintheDCpowersupplyloop(thetotallengthofthe48VDChotwire
andtheDCreturnwire)tonomorethan1Vtotal.Thisensuresthatthemaximumenergyisremovedfromthe
batterypriortodisconnectingthepowersupplyfromtheDCinputline.
Abaseradiotransmittingat50Wwilldrawupto7.4Acurrentwhenoperatingfroma54Vsource(nominal48
VDCsystem).Asvoltagedecreases(duetothestandbybatterydischarging)thecurrentwillincreaseproportionally
(sincethebaseradioappearstobeaconstantpowerload).Atthelowvoltagedisconnectpoint(42Vforanominal
6871022P86-A-November20123-19