A transformer is an electrical device, used in a system called the electrical power supply. It uses electromagnetic induction to transmute electric power from a single circuit to another. A power transformer is used as an interface to step-up or step-down electric power without changing the frequency of the alternating current.
Power transformers are generally liquid-immersed and have a lifespan of about thirty years. Depending on the range, power transformers are either small (500 – 7500 kVA), medium (100 MVA), or large (above 100 MVA).
Applications of Power Transformers
Power transformers are used in various electronic circuits and to alter voltage under high power conditions. Power transformers are used in power plants, industrial plants and electric utility plants in the transmission and distribution of electric power. In high voltage transmission networks, power transformers are used to step-up and step-down voltage for the purpose of heavy duty transmission. Power transformers form a part of the distribution network before it reaches the substations where distribution transformers are more widely used.
Power transformers do not connect directly to consumer electrical lines, meaning that the power fluctuations for a power transformer are very less. They work at very high loads with maximum efficiency because their cores are designed to do so. In comparison, a distribution transformer works more efficiently at lower loads since they are not fully loaded at all times and has much more power fluctuations since it is directly connected to consumer lines.
Construction and Working
A power transformer in India and elsewhere are designed to have maximum efficiency at high loads, and their cores are designed accordingly. Constructing a transformer is quite easy if the specifications of its requirements are known.
The transformer’s core consists of a laminated set of metal sheets, around which there are conducting coils wound. The primary coil has an incoming electric current that induces a magnetic force in the core which, in turn, induces an electromotive force or a voltage in the secondary coil. This is in accordance to Faraday’s law of induction, and there is absolutely no contact between the two coils of the transformer.
Specifications of Power Transformers
Power transformers india can either be single-phase transformers or three-phase transformers depending on their purpose. There are some specifications that must be considered when building a power transformer. Maximum voltage and power ratings, maximum secondary current rating and o/p type are some of these specifications. Typically, a power transformer has the following specifications:
- A 3Ø phase
- A frequency of 50-60 Hertz
- Primary voltage of 22.9 kV
- Secondary voltage of 6.6/3.3 kV
- A tap voltage of 23.9-R22.9-21.9-20.9-19.9kV
More specifically, the weight, dimension, and construction of a power transformer depend on its capacity, exciting voltage, and other such factors. For example, a power transformer with a capacity of 1000 KVA has an exciting current of 4.5 % and a voltage requirement of 1.3%; the height, depth, and width should correspond to 1700mm, 1960mm, and 2200mm respectively. This makes its total weight, including the volume of oil (900 liters), come up to 3500kg, giving it an efficiency of about 98.5 %. Similarly, the values of each dimension can be plotted according to the requirements of the transformer.
For different electrical appliances, the requirements of transformers are different even if the principle is the same. International standards make an important distinction between distribution transformers and power transformers in the sense that though they both form a part of power transmission, Distribution transformers India are concerned with the local transmission of power; whereas, power transformers are concerned with transmission between power generators and distribution circuits.