Transformers are the device which is capable of receiving AC power at one voltage and delivering it at another voltage. In this way transformer help in achieve better transmission efficiency, while transferring the power over longer distances with high voltages.
In this article we will go through the working and construction of a three-phase transformer, by starting from its simplest form. The basic working principle a transformer is based upon the electromagnetic induction. According to this principle varying magnetic flux associated with the loop will induce an electromotive force across it. Such a fluctuating magnetic field can easily be produced by a coil and alternating EMF system. A magnetic field a produced by a current carrying conductor around it.
With the fluctuating nature of the alternating current, the magnetic field associated with the coil will also fluctuate. This magnetic flux can be effectively linked to a secondary winding, with the help of a core made up a ferromagnetic material. This fluctuating magnetic field will induce an EMF in the secondary coils due to electromagnetic induction. Since the turns are arranged in a series, the net EMF induced across the winding will be the sum of the individual EMFs induced in each turn. Since through primary and secondary winding same magnetic flux is passing, the EMF per turn for both the primary and secondary coils will be the same.
Three-phase transformers are use three single phase transformers but their coil configuration are different. Here the primary and secondary coils sit concentrically. In a three phase transformer two more such winding are employed.
Transformers with high power ratings are designed with a special kind of winding which is known as Disc winding, Where separate disk windings are connected in series through outer and inner crossovers. The low voltage windings of a transformer are generally connected in a delta configuration and the high voltage linings are connected in a star configuration.Hence from a three-phase step up transformer we can draw four output wires which is a three phase power wires and one neutral.
High-voltage insulated bushings are required to bring out the electrical energy. The transformer core are made of thin insulated laminations steel. Such steel laminations are stacked together as shown to form a three-phase limbs. By using the thin lamination the energy losses due to eddy current formation are decreases. The low voltage winding are usually placed inside near the core
Different kind of energy loss occur during transferring power from the primary to secondary coil. All these types of energy losses are dissipated as heat energy. So for better performance of transformer it is usually immersed in a cooling oil, which dissipate the heat. The oil dissipates the heat through natural convection. The Oil when absorb heat will expand . A conservator tank which helps to accommodate for change in volume.
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