# Power Transformers

View Notes

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.

Q1. What Happens When we Overload a Transformer?

Ans: Generally overloading will take years to destroy a transformer. When we increase the load the windings heat up and then cool down again when it is decreased. In the overloading transformers can result in cracks in the insulation, since there is no oil to cool it and result in the failure of the transformer.

Q2. What is Inside a Power Transformer.

Ans: Transformers force is a static electricity equipment that is used in a number of ac voltage (current) into the same frequency of several or other values of voltage of equipment. When alternate current fills the primary winding then alternating flux is generated.

Q3. If we Overload a Transformer What Happens?

Ans: The output voltage would drop considerably when the transformer is overloaded. The voltage in our domestic plug will also be low. If we are using these plugs for usage of some devices in our home it may be dangerous. When the load increases then it heats up and the cooling down ratio decreases.

Q4. Till What Capacity a Transformer can be Overloaded?

Ans: Due to the continuous charging lode of a transformer, they are only designed for giving efficiency up to 50%. Only 50% load they can bear. Now, considering the particle constraint loading is to be considered upto a window of 50 to 60% loading for optimum operations.