illusions Posted March 4, 2008 Report Share Posted March 4, 2008 hi . m about to install 2 by 10kw motors using star delta starter. flc of each motor is 25A. what should be the size of the cable. Link to comment Share on other sites More sharing options...
chrisevo Posted March 4, 2008 Report Share Posted March 4, 2008 I would need to know how long cables are to be and of what type? Link to comment Share on other sites More sharing options...
Jay Tee Posted March 5, 2008 Report Share Posted March 5, 2008 hi . m about to install 2 by 10kw motors using star delta starter. flc of each motor is 25A. what should be the size of the cable. There are a lot of ways to determine the cable size since different type of cable may have different ampere rating. However, for minimum requirement, you may use the following formula: For DC and single phase motor S= (2.L.I. pf)/(C.VU) or S = (2.L.P)/(C.VU.U) For Three Phase motor: S=(1.73.L.I.pf)/(C.VU) or S = (L.P)/(C.VU.U) where S = cable size in mm sq L = cable length in meter I = Rated ampere P = power of motor in watt CU = Voltage drop allowable( such as 2.5% of usage voltage)..depend on country regulation U = Voltage pf = power factor C = conductivity of cable if Cu = 56, Al = 35, Fe = 8.5 To get the final result, S shall be divided with the temperature surrounding factor: 20 Deg C: 1.4 25 Deg C : 1.3 30 Deg C : 1.22 35 Deg C : 1.13 40 Deg. C : 1.00 45 Deg. C : 0.87 For example, S = 3.5 with surrounding temperature around 45 Deg. C, then the final result shall be (3.5)/(0.87). From here, you will select the cable size based on the standard manufacturer available like 1.5, 2.5, 4.0 and etc. For safety, I would suggest you choose one step higher then the final result. Link to comment Share on other sites More sharing options...
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