Question urgent for Sparks


Postby Jeffmo » Wed Jun 13, 2007 8:51 pm

Hi Sparks , i wonder if you could help me with what is probably an easy calculation for you . Can you tell me the maths for finding Zs if i have 10m of copper cable ( 1.5 / 1.00 mm )pvc twin/e if my Ze is 0.6 ohms. I have had a day of number crunching and my brain has melted .Please help as even the easy stuff now seems difficult .Cheers mate Jeff
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Postby BLAKEY1963 » Thu Jun 14, 2007 9:25 am

JEFFMO
MY KEYBOARD IS MAD AT THE MOMENT

RIGHT TO FIND ZS FROM YOUR INFORMATION

ZE = O.6 OMHS

10 METRES OF 1.5 TWIN + EARTH CABLE

R1 = 12.1 MILLIOMH PER METRE ( PHASE CONDUCTOR )
R2 = 18.1 MILLIOMH PER METRE ( C.P.C CONDUCTOR )

MULTIPLIER FOR CONDUCTOR OPERATING TEMPERATURE AT 20 DEGREES C = 1.2

LENGTH OF CABLE RUN = 10 METRES

TOTAL R1 + R2 = 10 X 30 .2 X 1.2 / 1000 = 0.36

ZS = ZE + R1 + R2

ZS = 0.6 + 0.36 = 0.96

TOTAL EARTH LOOP IMPEADANCE = 0.96 OMHS MR JEFFMO
Last edited by BLAKEY1963 on Thu Jun 14, 2007 10:54 pm, edited 2 times in total.
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Postby sparx » Thu Jun 14, 2007 11:40 am

Hi Jeff
sorry for late reply but been offline for a while;
Zs (system) = Ze(external loop L+E) plus R1+R2 (internal loop from con.unit L out to far end of circuit plus E conductor back to con. unit)
eg Ze + R1+R2= Zs.
you don't need to correct readings for temp. as in order to take resistance readings the circuit will be off load & at ambient room temp. which will be very close to tabulated readings in charts.
as a guide without looking tables up if 1.5 mm2 is say 0.12 Ohms then 1.0 should be 1/2 more ie 0.18 Ohms
giving Zs of 0.6+0.12+0.18= 0.9 Ohms
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Postby BLAKEY1963 » Thu Jun 14, 2007 10:15 pm

[quote="Jeffmo"]Hi Sparks , i wonder if you could help me with what is probably an easy calculation for you . Can you tell me the maths for finding Zs if i have 10m of copper cable ( 1.5 / 1.00 mm )pvc twin/e if my Ze is 0.6 ohms. I have had a day of number crunching and my brain has melted .Please help as even the easy stuff now seems difficult .Cheers mate Jeff[/quote]
JEFFMO
DISREGARDE PREVIOUS MESSAGE
TRY THIS

ZS = ZE+ R1 + R2
ZE = O.6 OMHS
R1 = 12.1MILLIOMH PER METRE
R2 = 18.1 MILLIOMH PER METRE

TOTAL R1 + R2 = LENGTH OF RUN X 30.2 X MULTIPLIER OF 1.2 / 1000

( MULTIPLIER OF 1.2 IS CORRECTION FACTOR FOR CONDUCTOR
OPERATING TEMPERATURE AT 20 DEGREES C )

ZS = ZE + R1 + R2 ( 10 X 30.2 X 1.2 / 1000 )

ZS = 0.6 ( ZE ) + R1+R2 ( 0.36 )

ZS = 0.96 OMHS
.
BLAKEY1963
Posts: 654
Joined: Wed Jun 13, 2007 10:57 pm


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