Power Transformer Working Principle, Types & Real-World Applications
A passive electrical device that transfers electrical energy from one electrical circuit to another or multiple circuits, is known as a transformer. In any one coil of transformer the varying current is produced in varying magnetic flux, in the transformers core. This includes a varying electromotive force across any of the other coils that would be around the same core.
Without the metallic connections between the two circuits electrical energy can be transferred between the separate coils. In 1831 the Faraday's law was introduced which stated the induced voltage effect in any coil due to changing magnetic flux encircled by the coil. Transformers are very commonly used in AC for increasing low voltage at high current or decreasing high AC voltage at low current.
Transformer Electronics
Transformers perform a great work in many systems, for example in AC. There are few different types of transformers as single and double phase voltage transformers. In the single phase voltage transformer there is no direct electrical connection between the two coil windings thereby also giving it the name of isolation transformer. Usually the primary winding is connected to the input voltage supply and transforms or converts the electrical powers into magnetic fields. Whereas the job of the secondary winding is to convert the magnetic field which is altering into electrical power producing the required output voltage.
Let us assume the transformers turn ratio assuming an ideal transformer and the phase angle.
\[\frac{N_{P}}{N_{S}} = \frac{V_{P}}{V_{S}} = n = \text{Turns Ratio as :}\] фp = фs.
The order of the number while expressing a transformer's turn ratio value is very important as the turn ratio 3:1 expresses a very difficult transformer relationship, then output voltage is the one in which the turns ratio is given as : 1:3.
Types of Power Transformers
Electrical power generation at a low voltage level is very cost effective. This low voltage power can be transmitted to the receiving end. If this low voltage power is transmitted then it results in greater line currents which indeed cause more line losses. But if the level of voltage of power is increased then the current of the power is reduced which causes reduction in ohmic in the system and cross sectional area of the conductor that is reduction in the cost of the system and it also improves the voltage of the system.
Transformers can be categorized in different ways, depending upon their use purpose and construction etc. sometimes these classifications overlap; that is a transformer can be both a setup transformer and a three phase transformer. Another classification of transformer is set up and set down transformers.
A set up transformer converts a low voltage and high current to high voltage and low current from the primary side of the transformer to the secondary side. A step down transformer converts high voltage and low current to the low voltage, high current from the primary side of the transformer to the secondary side. Electrical power, distribution and instrument transformers are some other transformers.
Construction of Power Transformer
The transformer consists of electric circuits, magnetic circuits, dielectric circuits, tanks, accessories. The main elements of a transformer are secondary windings and primary windings and steel core. Transformers core is made up of silicon steel so that it can provide a continuous magnetic path. Usually the core is laminated to minimize eddy current loss. The transformer's magnetic circuit consists of yoke and core, the circuit provides a path to the flow of magnetic flux. Laminated steel sheets are used to make the core of the magnetic transformers and the sheet consists of silicon steel assembled to provide a continuous magnetic path.
The transformer's electric circuit construction consists of primary and secondary windings usually made up of copper. The rectangular cross section of conductors are generally used for low voltage winding and also for high voltage winding for large transformers. According to the core construction in which the secondary and primary windings are placed around it, the transformer is named as shell type or the core type transformer.
Applications of Power Transformers
Transformers can easily alter from one voltage to another from higher to lower and from lower to higher. These transformers can be used in various electronic devices and circuits and are also available in various forms.
The application of power transformers includes distribution and transmission of electrical power. Power plants also use these transformers very widely. Industrial plants, traditional electricity utility companies are also few places where power transformers are used. High voltage transmission networks to step up and step down voltage, power transformers are used. For the transmission of heavy load these transformers are used. Compared with the distribution transformers these transformers are big in size, they are used in transmission and producing. Transformers are used as set up devices for the purpose of transmission so that the loss can be reduced to power flow with a specific amount. These transformers are designed to use the core parts for maximum and will function near to the keen point B-H curve.
FAQs on Power Transformers: Complete Physics Guide
1. What is a power transformer and what is its working principle?
A power transformer is a static electrical device that transfers electrical energy between two or more AC circuits. It works on the principle of mutual induction. When an alternating voltage is applied to the primary coil, it creates a changing magnetic field in the core. This changing flux induces a voltage in the secondary coil, allowing energy to be transferred without a direct electrical connection.
2. What are the main components of a power transformer?
The main components that make up a power transformer are:
- Laminated Core: Made from thin sheets of soft iron to provide a path for magnetic flux and reduce energy loss.
- Windings: These are the primary and secondary coils, typically made of insulated copper wire.
- Insulating Material: Such as insulating paper and oil, used to prevent short circuits between the windings and the core.
- Conservator Tank: A tank placed above the transformer to hold extra oil and allow for its expansion and contraction with temperature changes.
- Cooling System: Often consists of cooling tubes or fins that help dissipate the heat generated during operation.
3. Can you explain the difference between a step-up and a step-down transformer?
A step-up transformer is designed to increase voltage. It has more turns of wire in its secondary coil than in its primary coil. This is used at power plants to raise the voltage for efficient long-distance transmission. In contrast, a step-down transformer is used to decrease voltage and has fewer turns in its secondary coil than in its primary. These are commonly used in substations and local distribution networks to lower the voltage to a safe level for homes and businesses.
4. Where are power transformers used in the real world?
Power transformers are essential parts of the electrical power grid. They are used in two main places: at power generation stations to step up the voltage for efficient transmission over long distances, and at electrical substations to step down the voltage before it is distributed to consumers like homes, offices, and factories.
5. Why is the core of a power transformer made of laminated sheets instead of a solid block?
The core is laminated to minimise energy loss caused by eddy currents. A changing magnetic flux induces small, circulating currents within the iron core itself. In a solid core, these currents would be large, generating significant heat and wasting energy. By using thin, insulated iron sheets (laminations), the path for these currents is broken up, drastically reducing the eddy current loss and improving the transformer's efficiency.
6. Why can't a transformer operate on a DC (Direct Current) supply?
A transformer relies on a changing magnetic flux to induce a voltage in its secondary coil. A DC supply provides a constant current, which creates a steady, unchanging magnetic field. Without a change in magnetic flux, the principle of mutual induction does not work, and no voltage can be induced in the secondary winding. Therefore, a transformer is fundamentally an AC device.
7. What are the main ways a transformer loses energy during operation?
Even though transformers are highly efficient, they still have some energy losses. The main sources are:
- Copper Loss: Heat generated in the copper windings due to the resistance of the wire (also known as I²R loss).
- Iron Loss: Energy lost in the core, which includes Hysteresis Loss (from repeated magnetisation and demagnetisation) and Eddy Current Loss (from induced currents in the core).
- Flux Leakage: When some of the magnetic flux from the primary coil does not link with the secondary coil, resulting in an incomplete energy transfer.
8. What happens if you continuously overload a power transformer?
Overloading a power transformer forces it to carry more current than its design limit. This leads to excessive heat building up in the windings. If this continues, the high temperatures can damage the insulating material around the coils, causing it to degrade and crack. This can eventually lead to a short circuit and permanent failure of the transformer.
