Features Of On Load Transformer

  • Electric Circuit is made using electrolytic grade with 99.99% pure High-Quality Copper from our regular and reputed vendor HINDALCO & STERLITE with Foil winding in L.V coil of transformer.
  • Magnetic Circuit is made using step-lap design for lower losses and low magnetizing current of core by using high quality CRGO material with grades such as ZDKH, ZDMH, AMORPHOUS, MOH, etc.
  • High Dielectric Insulation property to withstand lightening impulse and voltage surges.
  • ONAN through natural convection for effective cooling through axial and radial ducts.

Technical Specifications

Onload Transformers are installed where voltage fluctuations from HV side are continuous. So onload transformer changes tap using AVR without any power-cut and give constant output voltage. Thus, over-all power consumption of industry gets optimized hence results in power savings.


Type Indoor/ Outdoor Pad Mounted
Voltage Class 11, 22, 33 kV
Vector Group Dyn11
No. of phase 3 phases
Frequency 50/60 Hz
Tap Range +5% To -15% in 1.25% steps in 17 position or +5% To -15% in2.5% steps in 9 Positions or as per requirement of customer.
Winding Material Copper/ AluminiumFoil.
Applicable Standards BIS-1180
Painting Epoxy, Polyurethane or specified by customer
Standard Fittings
Protective Devices
  • Buchholz Relay with alarm and trip contact for transformers from 500 KVA to 5000 KVA
  • Oil Temperature Indicator with alarm and trip contact for transformers from 630 KVA to 5000 KVA
  • Winding Temperature Indicator with alarm and trip contact for transformers from 800 KVA to 5000 KVA
  • Magnetic Oil Level gauge with alarm contact for transformers from 1250 KVA to 5000 KVA
Optional Accessories
  • Neutral C.T
  • Jacking Pads
  • Shut-off Valves
  • Annunciation/Inspection Window
  • Pressure Release Valve with contacts
Advantages of Foil Winding

For achieving losses as per BIS-1180 we have developed FOIL WINDING for L.V coil of the transformer. Following are main advantages of foil winding.

  • Temperature rise is lower due to high face-area for current flow.
  • High Mechanical strength towards AXIAL and RADIAL forces in comparison to conventional layer winding.
  • Inter-turn Fault is vanished out due to foil winding as compared to layer winding
  • No need of transposition due to foil winding which gives exact results as compared to conventional winding.
  • Increased reliability
  • Reduced size.
  • Higher ambient temperature operating capacity.
  • Improved electrical stress resistance.
  • Better overall regulation.
  • Temperature control copper foil dissipate heat more effectively than conventional layer winding.
  • Consistent performance-controlled copper losses.
  • These Process enhance the transformer’s short – circuit withstand capability.
  • Due to on load tap changer, the voltage at LV side remains in limit against the voltage fluctuation from HV side.
  • For changing tap, shut down of factory is not reliable. But due to on load transformer you can or RTCCchange the tap even when your factory is in full load.
  • As there is RTCC panel with AVR (Automatic Voltage Regulator), LV side voltage remains in desire range by changing tap automatically.
  • Due to on load transformer increase industrial machinery life’s, low maintenance & low power conception.