What is transformer its construction and types: Updated [2022]

What is Transformer?

A transformer is derived from two words transfer + form, which means to transfer electrical power from one circuit to another.

It should be noted that it has one great advantage; the input side that has a frequency also comes out in the same form as output, which means the frequency isn’t changed, which is one of the significant advantages of the Transformer.
They are used to decrease or increase the voltage of the electrical supply. It is essential for transmitting power station to your home.
Actually, it is a machine, but it doesn’t have any moving part, that is why it’s referred to as a static machine.

Transformer

Construction

A transformer has two main parts i.e.

Two windings
Metallic Core in which winding is wound.

Core provides a path for flux, so maximum flux passes through the Core; hence two types of losses will occur. Metallic Core :

These lose are;

1. Hysteresis losses
2. Eddy Current losses

Together these losses are called magnetic losses or Iron losses. To overcome these losses, we have to construct it in such a way that it should have minimum losses.

How to reduce Hysteresis losses?

Generally, Core is made up of high-grade silicon steel (to choose the best magnetic material we should choose the steel which has high permeability). It is because it minimizes hysteresis losses.

How to reduce Eddy current losses?

As the Core is made up of thin lamination almost 0.5 or 0.5mm, which reduces the eddy current. This lamination is isolated from each other by varnish.

Windings or Coils:

Electric Current passes through windings, so we need a material that has less Resistivity, so copper is used for carrying the Current. The windings are isolated from each other and are subjected to I^2R losses, which are also called as copper losses.

So it’s based on the arrangement of coils and windings. Transformers are divided, which is discussed below.

Transformer Accessories :

These are the transformer accessories which are really useful and protect the Transformer.

1. 1. 1. 1. Tank
        
        Tubes
        
        Conservator
        
        Oil level indicator
        
        Buchholz relay
        
        Breather and Silica gel
        
        Explosion vent
        
        Thermometer
        
        Bushing
        
        Drain cock
        
        Rail & Wheel

TRANK;

It provides protection to the Core and windings and accommodates oil for cooling and insulation.

The tank of a small transformer is made of sheet steel, and those of large Transformer is made of boilerplates.

TUBES;

Colling tubes or radiators are used for cooling.

CONSERVATOR;

Heat is produced in the Transformer due to power loss in it. Due to this heat, the oil expands, and its volume increases.

For this, some space has to be provided. The layer of oil is in contact with the air, so to reduce the contact area, a small tank is kept above the main tank.

This tank is joined to the main tank with a small pipe. The main tank is completely filled with oil. This little tank is called a conservator.

Oil LEVEL INDICATORS;

This is used to see the level of oil in the conservatory.

BUCHHOLZ RELAY;

Buchholz relay is a gas operator relay. There is one cylindrical chamber, which is joined between the transformer tank and the Conservator. There are two floats made of aluminum. A mercury switch is kept with the cork. The tube is in a slant position in a healthy condition, so the contacts inside remain open. When the fault in the Transformer is just beginning, a small amount of gas is produced in oil. Gas goes up as it is light and accumulates at the top of the relay. Due to this, the level of oil decreases, which causes the upper float to come down, and the top mercury tube comes in the horizontal position, which shorts the contacts. Due to this, the Auxiliary relay is energized, and through its contacts, the alarm sound in the control room. The operator takes action such reduce the load on the Transformer.

A large amount of gas is produced when serious faults occur in the Transformer. Oil also expands, and oil flows rapidly towards the conservatory. So the lower float goes up, and the mercury switch becomes horizontal due to which, the contacts in the tube are shorted. The trip coil of the circuit breaker is connected through these contacts, so the circuit breaker operates, and the Transformer is disconnected from the system.

BREATHER & SILICA GEL ;

When the oil heats up, the air in the conservatory goes out, and when oil cools, atmospheric air goes in the air to mix with the oil, which reduces the dielectric strength of the oil. Breather is used to absorb the moisture from the air going into the Conservator. Pieces of silica gel (CaCls) are kept in the breather. The property of silica gel is to absorb the moisture. When the air goes into the conservatory, the silica gel absorbs the moisture from the air, and the dry air goes into the conservatory.

The color of dry silica gel is blue, and it turns into pink when it is saturated with moisture. A small glass window is provided in the breather through which the color of silica gel can be seen. When the color of the silica gel turns out PINK, the silica gel is removed, and the fresh silica gel is filled. The wet silica gel can be heated and made dry for rescue.

EXPLOSION VENT;

The transformer tank is completely filled with oil. If the spark occurs in the Transformer due to fault, the oil decomposes, and gases are produced. Now the gas occupies more space than oil, so the pressure in the tank increases, and some time explosion may occur. To prevent this, an explosion vent is used. A small pipe is kept at the top of the tank. The pipe carries a thin diaphragm of metal sheet at the open end. Due to the increased pressure, the diaphragm is ruptured, and the gas and oil go out, and the pressure is released, and the explosion is prevented.

THERMOMETER ;

The thermometer pocket is provided for inserting thermometers for the measurement of temperature.

BUSHING ;

HT connection of the transformer tank. Now, tank earth at potential, as a result of this giving insulating support for HT wire. That’s why we use bushing.

- - - - > Porcelain bushing used up-to 20 VK,
      - > Oil field bushing used up-to 33KV,
      - > Synthetic resin bounded condenser used up-to 66KV.

DRAIN COCK;

Drain cock is provided at the bottom of the tank.

It is mainly used for removing oil and waste extricate.

RAIL& WHEEL;

It’s used to carry a transformer from one place to another place with the help of a wheel and rail.

Working Principles

The Transformer operates on mutual induction, which means when voltage is applied to coil or supply is connected to the coil, then flux is produced, and after that, poles are created, North pole and South pole as shown in the figure below.

Supply connected to the coil flux generated.

Waves are generated from the north pole, i.e., electrical lines of force to the south pole, which act as a magnet and then back linked to the north pole, so Electromotive force is produced, which is known as EMF. The process is known as self-induction, however, if you connect or place another coil to the coil where Current and voltage is flowing through it, then the flux will link to the other coil as well which known as mutual induction, so in the short term, if EMF is generated in the second coil due to the first coil, it is known as Mutual induction.

So in the transformer same mutual induction phenomenon occurs; there is no connection between one coil to another, but when u apply voltage at the primary coil, EMF is produced in another coil as well as shown in the figure.

Mutual Induction

Types

There are different kinds of transformers used in electrical systems. Each Transformer has its own purpose. You cannot use the same Transformer for different purposes, it may cause damages.

These are discussed as under;

1. 1. 1. 1. Step-up transformer
        
        Step-down Transformer
        
        Power transformer

Step Up:

As step-up transformers are defined as when Low voltage and high Current are applied at the input side, we will get high voltage low current at the output.

Step-up transformers transform low voltage and high current Ac to high voltage Low current Ac system. As shown in the figure;

Step Up Transformer

It should be noted that in the step-up Transformer, the number of turns in the primary coil is much less than several turns in Secondary coil.

When power is generated, and we want to send it to long-distance, then we use step-up transformers.

Step Down :

The step-down Transformer is just opposite to the step-up Transformer as when high voltage and low current is applied at the input side, we will get low voltage high current at the output.

Step down, transformers transform high voltage low current Ac to low voltage high current Ac system. As shown in the figure;

Step Down Transformer

It should be noted that in step down Transformer, the number of turns in the primary coil is much higher than then the number of turns in the Secondary coil.

Usually, for domestic purposes, we use step down transformers as if we want to decrease the voltage to 220v, then we use a step-down transformer.

Power :

The power transformers are used to transfer higher voltages from the grid to grid the ratings of power transformer, maybe 400KV, 200KV,50KV.

It depends on the transmission lines and also on distance.

Power Transformer

Distribution :

This type of Transformer has lower ratings like 11KV, 6.6KV 230V. As the power that comes to our home is due to the distribution transformer, it is basically a step-down transformer.
If you want to down the power, we use a distribution transformer, as shown in the figure below.

Distribution Transformer

Instrument :

Instrument transformer is an electrical device that is used to transform voltage as well as Current.

Instrument Transformers are utilized in the AC framework for estimation of electrical amounts, for example, voltage, current, power, vitality, power factor, recurrence. Instrument transformers are additionally utilized with defensive transfers for insurance of intensity framework.

The fundamental capacity of Instrument transformers is to step down the AC System voltage and Current. The voltage and the current degree of intensity framework are exceptionally high. It is troublesome and exorbitant to structure the estimating instruments for the estimation of such significant level voltage and Current. By large, estimating instruments are intended for 5 An and 110 V.

Instrument Transformer

The estimation of such enormous electrical amounts can be made conceivable by utilizing the Instrument transformers with these little evaluating estimating instruments. Hence it is the mainstream in the current force framework.

There are two types of instrument transformers.

1. 1. 1. Current Transformer(CT)
    2. Potential Transformer(PT)

Potential Transformer is also called a voltage transformer, the main function of it is to step down the voltage to a safe limit or value.

Potential Transformer

The current Transformer is used for protection and measuring. When the current in the circuit is high and not suitable for applying directly to the measuring instrument, in this case, the current Transformer is used to transform the high Current to the desired value that is suitable for the circuit.

Current Transformer

Single Phase Transformer;

A single-phase transformer is a static device that works on a principle of Faraday’s law of mutual induction. The Transformer transforms Ac power from one circuit to another.

There are two types of windings one is primary to which Ac voltage is connected and another secondary from which we take the output, which is already described below.

Three Phase Transformer;

A three-stage or three-phase transformer is a three-legged iron center. Every leg has a particularly essential and optional winding. Most force is scattered as three-stage AC.

Fundamentally the force organization generators produce power by pivoting 3 curls or windings through an attractive field inside the generator.

The formula ;

In the figure below, the different equations of transformers are given and also shown how to calculate the efficiency of the Transformer.

Efficiency of Transformer

Number of turns ratio calculation

USES OF TRANSFORMER

The Transformer has its own significance. In the current field according to the necessity and application of transformers, it has followings uses as given below;

Application

The most significant uses and use of Transformers are:

It can increase or decrease the degree level of Voltage or Current (when voltage builds, current declines, and bad habit versa because P =V x I, and power is the same ) in an AC Circuit.
It can increment or decrements the estimation of the capacitor, an inductor, or opposition in an AC circuit. It would be able to go through an impedance moving gadget.
It can be utilized to keep DC from going from one circuit to the other.
It can segregate two circuits electrically.
The Transformer is the primary motivation to transmit and disseminate power in AC rather than DC since the Transformer is not chipped at DC, so there are two challenges to transmit power in DC. In the DC Transition, the degree of voltage Step up by Buck and Boost Converter.
The fundamental use of the Transformer is to Step up ( Increase) or Stepdown (Decrease) the Voltage.
At the end of the day, Increase or decrease the degree of Current, while power must be the same.

Different Uses :

Some transformers work as step up or step down if it is step up, it steps up the voltage before transmission.
In the appropriation side, for business or residential utilization of power, the Transformer step down ( decrease) the degree of the voltage of 11kV to 220 V single stage and 440 V three-stage.
The Current Transformer and Potential Transformer likewise used to force framework and in the business. Additionally, it is used for impedance matching.
So these were the straight forward uses and use of a transformer.

Things To Remember

10 transformer safety practices for electricians and industrial professionals

The importance of proactive inspections in the safety of electrical transformers

Using industrial equipment that generates large voltages lapse in the handling of electrical transformers could cause costly equipment malfunctions and even deaths. This is the reason that inspection of electrical transformers is crucial. Regular inspections and maintenance can help detect potential issues early and avoid future problems.

Electrical transformers should be inspected for damaged connectors, worn-out power cords, and smells of burning and lost plugs, as well as malfunctioning parts, to avoid malfunctions and fire dangers. The maintenance team must pay close attention to the ISO 9001 requirements and UL CUL, UL VDE, CE standards to ensure a safe work environment for the equipment and electricians. (Source)

These safety tips for transformers apply to any transformer regardless of its maker or the manufacturer:

1. Ensure to inspect the electrical transformer before installation for any burnt smell, damaged parts, or irregularities in the continuity.

2. All maintenance work should only be done following the time the equipment has been disconnected and removed from the circuit before the system has been closed.

This is essential to ensure there isn’t any leakage of electrical current or continuity between the electrical current of the horse as well as the circuit.

3. The maintenance staff should be equipped with personal protective equipment that has been specifically designed to protect the workers when working on electrical transformers that produce high voltage.

4. Any modifications should not be made to electrical transformers that require over current protection. Over-current protection mechanisms in circuits and conductors should be adjusted to meet the manufacturer’s standards.

5. The transformer’s grounding must be maintained at all times. It stops the build-up of static charges and keeps the windings safe from coming into contact with the enclosures or core.

6. The transformer should be checked frequently to check for bolts, nuts or spare parts that have gotten into the.

7. The electrical transformer and the components that comprise it must be kept dry throughout the day since every contact may cause harm.

8. A sign-in sheet should be posted close to the electrical transformer, warning that people should stay clear of it so that workplace hazards can be avoided.

9. Anyone working with the transformer’s electrical components must be aware of the voltages used to power it.

10. If an anomaly or irregularity is noticed in the working of the transformer’s electrical circuit, it should be turned off, and all cables and power cords need to be removed before determining the part of the transformer that has been not working correctly.

Electrical transformers are a robust device and a vital source of energy for every industry operating with the help of electricity. Still, there are many hazards associated with this machine.

It is crucial to follow all necessary safety precautions to avoid any equipment destruction, electrical fire, or death and ensure that the operations are running smoothly at all times. (Source)

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What is transformer its construction and types: Updated [2022]