منتدى الهندسة الكهربية

[CENTER][CENTER][B][U][COLOR=#0000cc][F**T=Arial]C**trol Cables[/F**T][/COLOR][/U][/B][/CENTER][/CENTER]
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[F**T=Arial][COLOR=#000000]The main advantages of PVC Cables can thus be summarized as under:[/COLOR][/F**T][LIST][*][F**T=Arial][COLOR=#000000]The insulati** resistance and breakdown strength are practically unaffected by moisture. These cables are thus suitable for laying even under water.[/COLOR][/F**T][*][F**T=Arial][COLOR=#000000]Cables can be overloaded for short periods without any appreciable effect ** cable life.[/COLOR][/F**T][*][F**T=Arial][COLOR=#000000]The cables can be laid vertically and ** steep slopes as there is no impregnating compound involved.[/COLOR][/F**T][*][F**T=Arial][COLOR=#000000]The cables are flame retardant since PVC ignites with great difficulty and is self extinguishing.[/COLOR][/F**T][*][F**T=Arial][COLOR=#000000]These cables are immune to chemicals normally encountered in practice.[/COLOR][/F**T][*][F**T=Arial][COLOR=#000000]Due to their lightweight, PVC Cables are easy to install and handle. Small bending rapider permits the terminati** of these cables in limited space.[/COLOR][/F**T][*][F**T=Arial][COLOR=#000000]Low tensi** PVC Cables do not normally require sealing ends, when terminated indoor. The terminati**s can therefore be effected quickly and ec**omically.[/COLOR][/F**T][*][F**T=Arial][COLOR=#000000]PVC Cables have tough but smooth outer covering and are thus abrasi** proof.[/COLOR][/F**T][*][F**T=Arial][COLOR=#000000]PVC cables are not affected by vibrati**.[/COLOR][/F**T][*][F**T=Arial][COLOR=#000000]PVC Cables have high short circuit capacity since they can withstand a high transient temperature without any deformati** of insulati** or displacement of c**ductor.[/COLOR][/F**T][*][F**T=Arial][COLOR=#000000]PVC Cables have a l**g service life.[/COLOR][/F**T][/LIST][B][U][COLOR=#0000cc][F**T=Arial]General C**structi** of PVC Cables[/F**T][/COLOR][/U][/B]
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[B][U][COLOR=#0000cc][F**T=Arial]C**ductor[/F**T][/COLOR][/U][/B][F**T=Arial]
[COLOR=#000000]the c**ductor shall be composed of plain copper or aluminum wires complying with IS: 8130-1984. Mining Cables to be used in gassy mines shall be of copper c**ductor **ly.

[/COLOR][B][U][COLOR=#0000cc]Insulati**[/COLOR][/U][/B][/F**T]
[F**T=Arial][COLOR=#000000]The c**ductors are insulated with suitably compounded PVC, which is applied to the c**ductor by extrusi** process.[/COLOR][/F**T]
[B][U][COLOR=#0000cc][F**T=Arial]Core Identificati** & Colour Scheme[/F**T][/COLOR][/U][/B]
[F**T=Arial][COLOR=#000000]Cores are identified by colour scheme of PVC insulati**.[/COLOR][/F**T]
[B][COLOR=#0000cc][F**T=Arial]The following colour scheme is adopted.[/F**T][/COLOR][/B][COLOR=#0000cc][F**T=Arial][/F**T][/COLOR]
[CENTER][F**T=Arial][COLOR=#000000]**e core[/COLOR][/F**T]
[F**T=Arial][COLOR=#000000]Red, Black, Yellow or Blue[/COLOR][/F**T]
[F**T=Arial][COLOR=#000000]Two Core[/COLOR][/F**T]
[F**T=Arial][COLOR=#000000]Red and Black[/COLOR][/F**T]
[F**T=Arial][COLOR=#000000]Three Core[/COLOR][/F**T]
[F**T=Arial][COLOR=#000000]Red, Yellow and Blue[/COLOR][/F**T]
[F**T=Arial][COLOR=#000000]Four Core[/COLOR][/F**T]
[F**T=Arial][COLOR=#000000]Red, Yellow, Blue and Black (reduced neutral core is also Black)[/COLOR][/F**T]
[F**T=Arial][COLOR=#000000]Five core[/COLOR][/F**T]
[F**T=Arial][COLOR=#000000]Red, Yellow, Blue, Black and Light Grey[/COLOR][/F**T]
[F**T=Arial][COLOR=#000000]For cables having **** than 5 cores[/COLOR][/F**T]
[F**T=Arial][COLOR=#000000]Two adjacent cores (counting and directi**al) in each layer are coloured Blue & Yellow respectively and the remaining cores are Light Grey.[/COLOR][/F**T]
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[B][U][COLOR=#0000cc]Inner Sheath[/COLOR][/U][/B][/F**T]
[F**T=Arial][COLOR=#000000]For all cables having two or **** cores, a comm** covering (inner sheath) is provided over the laid up cores either by extrusi** or by wrapping of plastic or proofed tapes. Single core cables do not require inner sheath.[/COLOR][/F**T]
[B][U][COLOR=#0000cc][F**T=Arial]Armouring[/F**T][/COLOR][/U][/B]
[F**T=Arial][COLOR=#000000]Depending up** the applicati**, the cables can be armoured. The armouring can be Round Steel Wire or Steel Strips. In case of cables where diameter over the inner sheath does not exceed 13 mm, the armour c**sists of Galvanized Round Steel Wires; above this size, the armour can be Galvanized Flat Steel Strips or Galvanized Round Steel Wires as per customers' requirement. In case of single core cables intended for use of an A.C. Systems, the armouring shall be of Aluminum Wires/Stripes or any other n**-magnetic material.

Armouring of PVC Mining Cables c**sists of Galvanized Round Steel Wires/Strips, but wherever necessary, a few Tinned Copper Wires/Strips are also included to meet the resistance requirements of armouring for Mining Cables.[/COLOR][/F**T]
[B][U][COLOR=#0000cc][F**T=Arial]Outer Sheath[/F**T][/COLOR][/U][/B]
[F**T=Arial][COLOR=#000000]Over the armouring or in case of unarmoured mechanical c**trol cables, over the inner sheath (for single core cables over the insulati**), a tough outer sheath of PVC are applied by extrusi**. This is normally Black in colour. This provides a tough but smooth outer covering to PVC Cables. The trademark "HMT" al**g with the year/code of manufactured are embossed ** the outer sheath. Wherever desired the customer name can also be embossed ** the cable. The embossing script repeats at desired length of electrical c**trol cables[/COLOR][/F**T]
[B][U][COLOR=#0000cc][F**T=Arial]Type Designati**[/F**T][/COLOR][/U][/B]
[F**T=Arial][COLOR=#000000]The following code is used for designating the type of cable.[/COLOR][/F**T]
[CENTER][COLOR=#000000][B][F**T=Arial]C**stituents[/F**T][/B][F**T=Arial][/F**T][/COLOR]
[COLOR=#000000][B][F**T=Arial]Code[/F**T][/B][F**T=Arial][/F**T][/COLOR]
[F**T=Arial][COLOR=#000000]Aluminum c**ductor[/COLOR][/F**T]
[F**T=Arial][COLOR=#000000]A[/COLOR][/F**T]
[F**T=Arial][COLOR=#000000]PVC insulati**[/COLOR][/F**T]
[F**T=Arial][COLOR=#000000]Y[/COLOR][/F**T]
[F**T=Arial][COLOR=#000000]Steel round wire armour[/COLOR][/F**T]
[F**T=Arial][COLOR=#000000]W[/COLOR][/F**T]
[F**T=Arial][COLOR=#000000]Steel strip armour[/COLOR][/F**T]
[F**T=Arial][COLOR=#000000]F[/COLOR][/F**T]
[F**T=Arial][COLOR=#000000]Steel double round wire armour[/COLOR][/F**T]
[F**T=Arial][COLOR=#000000]WW[/COLOR][/F**T]
[F**T=Arial][COLOR=#000000]Steel double strip armour[/COLOR][/F**T]
[F**T=Arial][COLOR=#000000]FF[/COLOR][/F**T]
[F**T=Arial][COLOR=#000000]PVC outer sheath[/COLOR][/F**T]
[F**T=Arial][COLOR=#000000]Y[/COLOR][/F**T]
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[B][U][COLOR=#0000cc][F**T=Arial]Testing of PVC Cables[/F**T][/COLOR][/U][/B]
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[COLOR=#000000]Testing is a vital part of cable manufacturing and all raw materials and finished cables are thoroughly tested to ensure quality c**trol. HMT has a well equipped testing laboratory for carrying out electrical, mechanical and chemical tests which are required as per relevant specificati**s. The various tests as provided in the Indian Standards are carried out ** HMT Cables. These are classified in three different groups: [/COLOR][/F**T][LIST][*][F**T=Arial][COLOR=#000000]Routine Tests[/COLOR][/F**T][*][F**T=Arial][COLOR=#000000]Type Tests[/COLOR][/F**T][*][F**T=Arial][COLOR=#000000]Acceptance Test[/COLOR][/F**T][*][F**T=Arial][COLOR=#000000] [/COLOR][/F**T][/LIST][B][U][COLOR=#0000cc][F**T=Arial]Routine Tests[/F**T][/COLOR][/U][/B]
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[COLOR=#000000]The following tests c**stitute Routine Tests, which are carried out ** each and every length of cable before it leaves the factory:[/COLOR][/F**T]
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[B][U][COLOR=#0000cc]C**ductor Resistance Test[/COLOR][/U][/B][/F**T]
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[COLOR=#000000]This test ensures that c**ductor resistance is with the specified limits, thereby ensuring that the c**tinuity of c**ductor is maintained throughout the cable length and that the c**ductor has the required cross secti** area. The DC resistance is measured at room temperature and is then corrected to standard reference temperature at 20°C.[/COLOR][/F**T]
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[B][U][COLOR=#0000cc]High Voltage Tests[/COLOR][/U][/B][/F**T]
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[COLOR=#000000]This test ensures that the insulati** will safely withstand the rated voltage ****** permissible normal operati**.[/COLOR][/F**T]
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[B][U][COLOR=#0000cc]Type Tests[/COLOR][/U][/B][/F**T]
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[COLOR=#000000]These tests are carried out ** samples taken from each producti** lot. They are carried out to prove c**formity as regards the general qualities and design to the specificati** of particular type of cable. These tests are enumerated in the relevant Indian Standards.

[/COLOR][B][U][COLOR=#0000cc]Acceptance Tests[/COLOR][/U][/B][/F**T]
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[COLOR=#000000]The customers can request the various acceptance tests as provided in the relevant Indian Standard to be carried out before accepting the cables.[/COLOR][/F**T]
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