Parts of transformer and its function

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These are the main parts of a High Power Three Phase Electrical Transformer

  • Metallic core 
  • Holding Frame
  • Winding
  • Tank
  • On Load Tap Changer
  • Bushing and terminals
  • Radiator wings/Cooling tubes
  • Breather
  • Bucholz Relay
  • Explosion valve/Gas Release valve
  • Control panel
Lets discus each part one by one
  • Metallic Core: This forms the magnetic circuit of the transformer, the core not only holds the  three phase winding (LV and HV both) but also provide low reluctance path for the magnetic flux produced by the winding carrying alternating current. The flux of one winding link with the other winding while completely remain confined in the core. Core is made up of high grade silicon steel sheets, each sheet of core in known as lamination. The core is laminated to reduce eddy current loss. The material of core is popularly known as CRGO means Cold Rolled Grain Oriented which means during preparation of steel sheets for the core the sheets are made by pressing (rolling) relatively cold metal dough through rollers, makes the grains of the sheet to get aligned in one direction. The steel sheets offers low magnetic reluctance in the direction of oriented grains. The steel sheets are cut by using punching machines in special shapes and are arranged to form complete core of the transformer. 
crgo core of electrical transformer shell type construction
Laminated three phase high power transformer metallic core

  • Holding Frame: Steel frame is used to hold all the laminations of the core so that during working of transformer the laminations remain braced against heavy electromagnetic forces produced due to varying flux in the core. The frame must be made ho high quality steel so that it not only bare the mechanical load of the core and also of the three phase winding.
high quality transformer core frame 100 mva
Holding Frame of thee phase transformer

  • Winding: Winding for each phase is made up of copper conductor in three phase high power transformer. conductors are covered with insulating paper taps so that no short circuit will occur between winding turns.
paper tap insulation on transformer winding
Copper winding of one phase of a high power transformer 
First a layer of paper is used over each leg/limb of shell type core. wooden strips are placed over periphery of limb at equal distance which holds wooden separators. The separators are place between each winding disc.


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