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Cable Calc Question
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<blockquote data-quote="viperrowe2606" data-source="post: 509663" data-attributes="member: 33782"><p>Hi all, really hope someone can help me as I am doing something wrong when it comes to cable calcs, I am currently working my way through my lvl 3 EAL. Would someone be able to work through this question so i can see where i am potentially going wrong. Thanks in advance.</p><p></p><p>TN C S = 0.35</p><p></p><p>Ambient temp = 20</p><p></p><p>3ph DB (BS EN 60898)</p><p></p><p>3ph circuit for car lift, wired in pvc singles in trunking with 3 other circuits, circuit length 8M.</p><p></p><p>3 ph supply to a two post vehicle lift: 400 V 3 kW with a p.f of 0.85,</p><p></p><p>My calcs so far:</p><p></p><p>3000/ 1.732x4000.85 = </p><p></p><p>Ib = 5.094A</p><p></p><p>In = 6A (type C) (6A ≥5.094A)</p><p></p><p>6A/0.65(cg)</p><p></p><p>Iz = 9.23A</p><p></p><p>It = Cable Size = 1mm2</p><p></p><p>38x5.094x8/1000 =</p><p></p><p>Voltage drop = 1.54V</p><p></p><p>36.20(R1+R2) x 1.20(multiplier table I3 OSG) x 8 / 1000 = 0.34</p><p></p><p>0.34+0.35(Ze) = </p><p></p><p>Zs = 0.69</p><p></p><p>230/0.69 = </p><p></p><p>Isc = 333A</p><p></p><p>Adiabatic (0.2s as 3ph?) = 1.29mm (needs to be same or smaller than line?)</p><p></p><p>I must be doing something wrong, please help.</p></blockquote><p></p>
[QUOTE="viperrowe2606, post: 509663, member: 33782"] Hi all, really hope someone can help me as I am doing something wrong when it comes to cable calcs, I am currently working my way through my lvl 3 EAL. Would someone be able to work through this question so i can see where i am potentially going wrong. Thanks in advance. TN C S = 0.35 Ambient temp = 20 3ph DB (BS EN 60898) 3ph circuit for car lift, wired in pvc singles in trunking with 3 other circuits, circuit length 8M. 3 ph supply to a two post vehicle lift: 400 V 3 kW with a p.f of 0.85, My calcs so far: 3000/ 1.732x4000.85 = Ib = 5.094A In = 6A (type C) (6A ≥5.094A) 6A/0.65(cg) Iz = 9.23A It = Cable Size = 1mm2 38x5.094x8/1000 = Voltage drop = 1.54V 36.20(R1+R2) x 1.20(multiplier table I3 OSG) x 8 / 1000 = 0.34 0.34+0.35(Ze) = Zs = 0.69 230/0.69 = Isc = 333A Adiabatic (0.2s as 3ph?) = 1.29mm (needs to be same or smaller than line?) I must be doing something wrong, please help. [/QUOTE]
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