COREMATERIAL Clause Samples
COREMATERIAL. 5.1.1 Transformercoreshallbewoundcoretypeconstructionusingnewandhighqualitycoldrolledgrain oriented (CRGO)steelwith heat resistant insulating coatingorAmorphousmetal.
5.1.2 Thebiddershouldofferthecoreforinspectionandapprovalbythepurchaserduringmanufacturingstage . CRGO steel for core shall be purchased only from the approved vendors, list of which is available at ▇▇▇▇://▇▇▇▇.▇▇▇▇▇▇▇▇▇▇▇▇▇▇.▇▇▇/ims/ComponentList/Power- former%20upto%20420%20kV-CM%20List.pdf
5.1.3 Thetransformershallbesuitableforoverfluxing(duetocombinedeffectofvoltageandfrequency)upto1 2.5%withoutinjuriousheating.Theoperatingfluxdensityshallbesuchthatthereis a clear safemargin overtheoverfluxinglimitof12.5%.
5.1.4 No- loadcurrentshallnotexceed3%offullloadcurrentandwillbemeasuredbyenergizingthetransformeratr atedvoltageandfrequency.Increaseof12.5%ofratedvoltageshallnotincreasetheno-loadcurrent by6%offullloadcurrent.
5.1.5 Please refer to “Check-list for Inspection of Prime quality CRGO for Transformers”
COREMATERIAL. 6.1.2.1 Thecoreshallbestack/woundtypeofhighgradeColdRolledGrainOrientedorAmorphousCoreannealed steellaminationhavinglowlossandgoodgrainproperties,coatedwithhotoilproof insulation,boltedtogether and tothe framesfirmly to prevent vibrationornoise. The coreshallbestressrelievedbyannealingunderinertatmosphereifrequired.Thecompletedesignofcore mustensurepermanencyofthecorelosswithcontinuousworkingofthetransformers.Thevalueofthema ximumfluxdensityallowedinthedesignandgradeoflaminationusedshallbeclearly statedintheoffer.
6.1.2.2 Thebiddershouldofferthecoreforinspectionandapprovalbythepurchaserduringmanufacturingstage . CRGO steel for core shall be purchased only from the approved vendors, list of which is available at ▇▇▇▇://▇▇▇▇.▇▇▇▇▇▇▇▇▇▇▇▇▇▇.▇▇▇/ims/ComponentList/Power- former%20upto%20420%20kV-CM%20List.pdf
6.1.2.3 Thetransformerscoreshallbesuitableforoverfluxing(duetocombinedeffectofvoltageandfrequency) upto12.5%withoutinjuriousheatingatfullloadconditionsandshallnotgetsaturated. Thebiddershallfurnishnecessary designdatainsupportof this situation.
6.1.2.4 No- loadcurrentupto200kVAshallnotexceed3%offullloadcurrentandwillbemeasuredbyenergisingthetra nsformeratratedvoltageandfrequency.Increaseof12.5%ofratedvoltageshall notincreasetheno- loadcurrent by 6%of full loadcurrent. No- loadcurrentabove200kVAandupto2500kVAshallnotexceed2%offullloadcurrentandwillbemeasured byenergisingthetransformeratratedvoltageandfrequency.Increaseof12.5%ofratedvoltageshall notincreasetheno-loadcurrentby 5%offull loadcurrent.
6.1.2.5 Please refer to “Check-list for Inspection of Prime quality CRGO for Transformers” attached at Annexure-A. It is mandatory to follow the procedure given in this Annexure.