Power Transformer

A power transformer is an electrical device consisting of one coil of wire placed in close proximity to one or more other coils, used to couple two or more alternating-current (AC) circuits together by employing the induction between the coils. The coil connected to the power source is called the primary coil, and the other coils are known as secondaries. A power transformer in which the secondary voltage is higher than the primary is called a step-up power transformer; if the secondary voltage is less than the primary, the device is known as a step-down power transformer. The product of current time’s voltage is constant in each set of coils, so that in a step-up power transformer, the voltage increase in the secondary is accompanied by a corresponding decrease in the current.

  • Power Transformers are used in Transmission network so they do not directly connect to the consumers, so load fluctuations are very less. The average loads are nearer to full loaded or full load and these are designed in such a way that maximum efficiency at full load condition. These are independent of time so in calculating the efficiency only power basis is enough.
  • These are also used in Distribution Network so directly connected to the consumer so load fluctuations are very high. These are not loaded fully at all time. Average loads are about only 75% of full load and these are designed in such a way that max efficiency occurs at 75% of full load. As these are time dependent the all day efficiency is defined in order to calculate the efficiency.
  • Power transformers are used for transmission as a step up devices so that the I2r loss can be minimized for a given power flow.

Power transformer is designed for maximum efficiency at 100% load as it always runs at 100% load being near to generating station.




Technical Specifications

  • 'Tap Changer' options available
  • "Off Circuit Manually Operated" and "On Load Tap Changer" (OLTC) with AVR and RTCC panel
  • Prime quality, low loss, high permeability 'Cold Rolled Grain Oriented' silicon steel for core to achieve low no load losses
  • Electrolytic copper with insulating paper multi covered round wires and strips for both the primary and secondary windings to achieve low load losses
  • ONAN /ONAF cooling with conventional pressed steel radiators
  • Terminal arrangement is done for primary and secondary as per site requirements in these power distribution transformers and single phase distribution transformers
  • Low viscosity power distribution transformer oil with in numerous superior grades for specific usage


  • Rating
  • No load loss
  • Impedance
  • Flux density of core
  • Current density of winding
  • Overall tank dimension


  • One of the major advantages of power transformer is that they have outstanding capability to survive overloads and Tailor-made to suit customer requirements.
  • These are best for use in outdoor, exposed moisture, salt or dust laden atmospheres and are widely employed in chemical plants, oil and gas terminals where regular maintenance of the transformers is not possible because of poor accessibility factors.

Most Suitable for

  • Industrial Purposes
  • Electricity Board
  • Domestic and Consumer Transformers
  • Wind Mill Power transmission
  • ordinance factories
  • Defence departments
  • navel & air force units
  • Power generation houses & Electricity boards
  • Atomic power stations
  • CPWD, PWD, Dairy department, Railways etc.