# 2021-10-30 Electrical Tranformer Design

It is impossible to explain the construction of the most common forms of transformer in any manner so clear and concise as to enable an inexperienced person easily to comprehend the operation of the most common form of transformer.

One must understand the theory of electrical science fully in order to thoroughly comprehend the operation of transformers, but, in order to use this great agent in many practical ways, without understanding theory, it is almost necessary to be sufficiently familiar with it to grasp, in a general way, the principles of the operation of transformers.

It is very difficult to make anyone understand, even after explanations, that all three wires are in circuit at all times, although only two are in circuit at the same time. The reason for this lies in the fact that the wire of the one circuit is in the magnetic field of the two poles of the core of the transformer while it is not in the field of the second circuit, while at the same time the wire of the second circuit is in the field of the first circuit while it is not in that of the second circuit.

Yet, at any instant, each of these two circuits has a current of amagnitude proportional to the current of the other. For this

## Transformer simplified Calculation :

The proportion of voltage of source to load is called matchingtransformer.Example: Given,Voltage of load is 20v.Voltage of source is 6V.Then matching transformer is 6/20 =3/5.

### Voltage Transformer :

The difference of voltage between 2 points is called difference of voltageof that point.

### Power Transformer :

The difference of power between 2 points is called difference of power of that

point.

Calculation: The difference of power P in volts and current in Amp in one

point and difference in power in another point is equal to differenceof voltage in that point.

Example: P in given point is 4 and in another point is 3 .Then difference in P in this point is 4- 3 =1.

### Current Transformer:

The difference of current in one point and difference of current in another

point is equal to difference of voltage in these point.

Example: P in given point is 4 and in another point is 3 .Then difference in P in this point is 4- 3 =1.

Power Factor: Power factor is the ratio of real power and apparent power.

This is also called apparent power. It is called apparent power because it is measured by voltmeter and ampmeter. It is called apparent power because it is taken from voltage and current generated by the real power. It is called apparent power because it represents the useful generated power and real generated power.

## Prefixes

The word "transformer" is the common name for the passive electrical component that is used to step down (transform) voltages and step up (transform) current in an alternating current system. Transformers are used to match voltages between a supply and a load. Transformers allow a direct current power supply to a consumer be connected to a supply voltage while alternating current can be connected to a supply voltage while alternating current power supply . Transformers change both the voltage and the current in a power system.

Power transformers increase voltage from a low value to a higher value to feed a load while reducing the current from a higher value to a lower value. In power transmission systems, power transformers designed for high power values up to a few MW are used to increase the voltage for efficient transmission over long distances and to reduce the voltage for efficient distribution to a load.

These types of power transformers are not three-phase a.c. but a.c. power that is generated from a.c. power by a process called a.c. power rectification. The output of a.c. power transformers is usually a.c. power. In other power distribution systems, such as a.c. power distribution systems in commercial and residential buildings, power transformers designed for low power values from a few to a few hundred VA are used to step up the voltage from a.c. power generated from a.c. power source, such as the public grid, to connect the load with the power grid.

**There are three types of transformer based on their use.**

Transformers used in power transmission systems

Transformer used in power distribution systems

Transformers used in electronic circuits for power conversion

and power control.

**Power transformers are commonly used for three purposes.**

Power transmission

Power distribution

Power conversion

Transformers used in power transmission systems are designed to transform voltage and current. These transformers can handle high power, up to several megawatts. They are heavy, large, very expensive, and they require maintenance every year.

A power transformer is designed to connect electrical loads located far apart. They are physically too large for residential or commercial use. They are typically found in power stations, public utilities, and large factories. Metallurgical insulation is used to prevent dangerous leakage of electromagnetic fields.

Power transformers are used to increase the voltage for efficient transmission over long distances and reduce the voltage for efficient distribution to loads.

Power can be transmitted by high voltage ( HV ) AC transmission over a limited distance, the distance depending on the voltage of the supply. The prevailing voltages are usually 110, 220 or more. For longer distances, or where the voltage is too low, the power is transformed to a lower voltage by the use of special transformers.

Networks designed to supply Diesel generators, can have the same voltages as the normal system. Power transformers are sized to match the supply voltage to the requirements of the load. A transformer used to supply 80 kV to a load will have a secondary winding with a high secondary voltage and low secondary current.

Using transformers to increase voltages is more efficient. Transmission distances are greater, more power is transmitted over the same wire size, and the load is more dispersed. Under normal conditions, transformation ratios of two to one are used.

Power transformers are designed to work with both 3-phase and 1-2-3 phase power. When three-phase power is used, the power is reduced when it leaves the transformer. A three-phase transformer will reduce the power by one third, while a two-phase transformer will reduce the power by one half. When using a three-phase power transformer, the primary voltage must be the same as the secondary voltage.

## The Power Transformer

It is very difficult to make anyone understand, even after explanations, that all three wires are in circuit at all times, although only two are in circuit at the same time. The reason for this lies in the fact that the wire of the one circuit is in the magnetic field of the two poles of the core of the transformer while it is not in the field of the second circuit, while at the same time the wire of the second circuit is in the field of the first circuit while it is not in that of the second circuit. Yet, at any instant, each of these two circuits has a current of magnitude proportional to the current of the other. For this reason, the transformer is called a step-up transformer.

If two step-up transformers having primary and secondary windings of the same number of turns and the same size and without any interconnecting wires between them be used:

1: To step-up voltage and to step-down current; and

2: To step down voltage and to step-up current then these transformers will have no effect on each other, as one will be doing exactly what the other is doing. In the first place the wire of the first circuit will always be in the magnetic field of the second circuit and the wire of the second circuit will always be in the magnetic field of the first circuit. In the second place each circuit will have a current of magnitude proportional to the other, so the voltage will be the same and there will be no effect on either circuit.

The transformer can be used as a regulator by interchanging the primary and secondary circuits. As the currents will be the same for both transformers, the voltage will be the same, but the voltage will be increased as the current will be decrease. In this case the current of the load current will be greater than the current supplied by the source. Since the voltage is increased, the power lost in heating the windings will also be increased. To increase the current a smaller number of turns should be used.

When a transformer has a low voltage secondary winding and a high voltage primary winding it is called a step-down transformer. The structure of a step-down transformer is the same as a step-up transformer, but interchanging the positions of the two windings. A step-down transformer is used when the load is located near the voltage source. The voltage of the secondary winding of a transformer is proportional to the number of turns.

A step-down transformer is used when the load is located near the voltage source. of the secondary winding of a transformer is proportional to the number of turns.

A step-down transformer is used when the load is located near the voltage source.