Electric Transformers

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Electric transformers

Electrical transformers are machines that transfer electricity from one circuit to another with changing voltage level but no frequency change. Today, they are designed to use AC supply, which means that fluctuation in supply voltage is impacted by the fluctuation in the current. So, an increase in current will bring about an increase in the voltage and vice versa.

Transformers help improve safety and efficiency of power systems by raising and lowering voltage levels as and when needed. They are used in a wide range of residential and industrial applications, primarily and perhaps most importantly in the distribution and regulation of power across long distances.


The Construction of an Electrical Transformer

The three important components of an electrical transformer are a magnetic core, primary winding, and secondary winding. The primary winding is the part that is connected to an electrical source, from where magnetic flux is initially produced. These coils are insulated from each other and the main flux is induced in the primary winding from where it is passed to the magnetic core and linked to the transformer’s secondary winding through a low reluctance path.

The core relays the flux to the secondary winding to create a magnetic circuit that closes the flux, and a low reluctance path is placed within the core to maximize flux linkage. The secondary winding helps complete the movement of the flux that begins at the primary side, and using the core reaches the secondary winding. The secondary winding is able to pick momentum because both windings are wound on the same core and hence their magnetic fields help to create motion. In all the types of transformers, the magnetic core is assembled by stacking laminated steel sheets leaving the minimum required air-gap between them to ensure the continuity of the magnetic path.

 

Functioning of transformer

An electrical transformer uses Faraday’s electromagnetic induction law to work – “Rate of change of flux linkage with respect to time is directly proportional to the induced EMF in a conductor or coil”.

A transformer’s physical basis lies in the mutual induction between two circuits that are linked by a common magnetic flux. It is usually equipped with 2 windings: primary and secondary. These windings share a magnetic core that is laminated, and the mutual induction that takes place between these circuits helps transfer electricity from one point to another.

Depending on the amount of linked flux between the primary and secondary windings, there will be different rates of change in flux linkage. To ensure maximum flux linkage, i.e. maximum flux passing through and linking to the secondary winding from the primary, a low reluctance path is placed common to both windings. This leads to greater efficiency in working performance, and forms the core of the transformer.

The application of alternating voltage to the windings in the primary side creates an alternating flux in the core. This links both windings to induce EMF in the primary as well as the secondary side. EMF in the secondary winding causes a current, known as load current, if there is a load connected to the secondary section.

This is how electrical transformers deliver AC power from one circuit (primary) to another (secondary), through the conversion of electrical energy from one value to another, changing the voltage level but not the frequency.


Electrical Transformer: Efficiency and Losses

An electrical transformer does not employ any moving parts to transfer energy which means that there is no friction and hence no windage losses. However, electric transformers do suffer from negligible copper and iron losses. Copper losses occur due to heat loss during the circulation of currents around the copper windings, resulting in loss of electrical power. This is the greatest loss in the operation of an electrical transformer. Iron losses are caused by the lagging of the magnetic Molecules that lie within the core. This lagging happens in response to the alternating of the magnetic flux which results in friction and this friction produces heat which leads of loss of power in the core. This loss can be greatly reduced if the core is constructed from special steel alloys.

The intensity of power loss determines the efficiency of an electrical transformer and it is represented in terms of power loss between the primary and secondary windings. The resulting efficiency is then calculated in terms of ratio of the power output at the secondary winding to the power input at the primary winding. Ideally, the efficiency of an electrical transformer is anywhere between 94% to 96%


Types of Transformers

Electrical transformers can be classified into different categories depending upon their end-use, construction, supply, and purpose.


On the Basis of Design

  • Core Type Transformer This transformer features two horizontal sections with two vertical limbs and a rectangular core with a magnetic circuit. Cylindrical coils (HV and LV) are placed on the central limb of the core type transformer.
  • Shell Type TransformerThe shell type transformer has a double magnetic circuit and a central limb with two outer limbs.


On the Basis of Supply

  • Single Phase TransformerA single-phase transformer has only one set of windings. Separate single-phase units can offer the same results as three-phase transfers when they are externally interconnected.
  • Three Phase TransformerA triple-phase (or three-phase) transformer has three sets of primary and secondary windings to form a bank of three single phase transformers. The three phase transformer is mainly used for generation, transmission and distribution of power in industries.

On the Basis of Purpose

Step Up Transformer

This type is determined by the number of turns of wire. So, if the secondary set has a greater number of turns than the primary side, it means that the voltage will correspond to that, which forms the base of a step up transformer.

Step Down Transformer

This type is typically used for stepping down the level of voltage in the power transmission and distribution Network and so its mechanism is the exact opposite of a step up transformer.

These transformers are used to relay and protect instruments simultaneously.


On the Basis of Cooling

  • Self-Cooled Oil-Filled TransformersThis type is generally employed in small transformers of up to 3 MVA and is it designed to cool itself by the surrounding air flow.
  • Water-Cooled Oil-Filled TransformersThis type of electrical transformer employs a heat exchanger to facilitate the transfer of the heat from the oil to the cooling water.
  • Air-Cooled (Air Blast) TransformersIn this type of transformer, the heat that is generated is cooled with the help of blowers and fans that force the circulation of air on the windings and the core.


Main Characteristics of a Transformer

All transformers share some common features regardless of their type:

  • The frequency of input and output power is the same
  • All transformers make use of electromagnetic induction laws
  • The primary and secondary coils are devoid of electrical connection (except for auto transformers). The transfer of power is through magnetic flux.
  • No moving parts are required to transfer energy, so there are no friction or windage losses as with other electrical devices.
  • The losses that do occur in transformers are smaller than those in other electrical devices, and include:
    • Copper loss (electrical power lost in the heat created by circulation of currents around the copper windings, considered the heaviest loss in transformers)
    • Core loss (eddy current and hysteresis losses, caused by lagging of magnetic molecules in response to the alternating magnetic flux within the core)

Most transformers are very efficient, delivering between 94% to 96% energy at full load. Very high capacity transformers may deliver up to 98%, especially if they operate with constant voltage and frequency.


Uses of Electrical Transformer

The major uses of an electrical transformer include:

  • Raising or lowering the voltage level in the circuit of an AC.
  • Increasing or decreasing the value of an inductor or capacitor in an AC circuit.
  • Preventing the passage of DC from one circuit to another.
  • Isolating two electric circuits.
  • Stepping up the voltage level at the site of power generation before the transmission and distribution can take place.

Common applications of an electrical transformer include pumping stations, railways, industries, commercial establishments, windmills and power generation units.

 


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An electric transformer is a static device that transfers energy by electromagnetic induction. A transformer consists of two or more coils of wire wound around a core. The coils are insulated from each other and from the core. When an alternating current (AC) is passed through one coil, it creates a Magnetic Field. This magnetic field induces an AC voltage in the other coil. The voltage in the second coil is proportional to the number of turns in the coil and the magnetic flux density.

Transformers are used to step up or step down voltage. A step-up transformer increases the voltage, while a step-down transformer decreases the voltage. Transformers are also used to isolate two circuits from each other.

Transformers are used in a wide variety of applications, including power distribution, electronics, and telecommunications. They are also used in medical equipment, industrial machinery, and many other applications.

Transformers are very efficient devices. They can transfer power with very little loss. Transformers are also very reliable devices. They can operate for many years without any problems.

Transformers are safe devices. They do not produce any harmful emissions. However, they can be dangerous if they are not properly installed or maintained.

Transformers require very little maintenance. They should be inspected regularly for signs of damage. If a transformer is damaged, it should be repaired or replaced immediately.

Transformers can be troubleshooted by checking the voltage and current levels. If the voltage or current levels are not correct, the transformer may be damaged.

Transformers can be tested by using a variety of methods. One common method is to use an ohmmeter to measure the resistance of the windings. Another common method is to use an oscilloscope to measure the voltage and current waveforms.

Transformers are manufactured to a variety of standards. The most common standard is the American National Standards Institute (ANSI) standard. Other common standards include the International Electrotechnical Commission (IEC) standard and the British Standards Institution (BSI) standard.

The first transformer was invented in 1831 by Michael Faraday. Faraday discovered that an electric current could be induced in a coil of wire by a changing magnetic field. This discovery led to the development of the transformer.

Transformers have come a long way since Faraday’s invention. Today, transformers are used in a wide variety of applications. They are an essential part of the modern world.

The future of transformers is bright. They are likely to become even more efficient and reliable in the future. They are also likely to be used in new and innovative applications.

What is a transformer?

A transformer is a device that transfers electrical energy from one circuit to another without a change in frequency. It does this by using electromagnetic induction to create a magnetic field that induces a voltage in a second circuit.

How does a transformer work?

A transformer consists of two coils of wire that are wrapped around a ferromagnetic core. The primary coil is connected to the input voltage, and the secondary coil is connected to the output load. When current flows through the primary coil, it creates a magnetic field. This magnetic field induces a voltage in the secondary coil. The voltage in the secondary coil is proportional to the number of turns in the secondary coil and the ratio of the number of turns in the primary coil to the number of turns in the secondary coil.

What are the different types of transformers?

There are two main types of transformers: power transformers and audio transformers. Power transformers are used to transmit and distribute electrical power. Audio transformers are used to amplify and reproduce Sound.

What are the advantages of using a transformer?

There are several advantages of using a transformer. Transformers can be used to increase or decrease voltage, which can be useful for a variety of applications. Transformers can also be used to isolate two circuits from each other, which can be important for safety reasons.

What are the disadvantages of using a transformer?

There are a few disadvantages of using a transformer. Transformers can be bulky and heavy, which can make them difficult to transport. Transformers can also be expensive, depending on the size and type of transformer.

What are some safety considerations when using a transformer?

There are a few safety considerations when using a transformer. Transformers should always be used with the proper insulation to prevent shock. Transformers should also be used with the proper voltage rating to prevent damage.

Where are transformers used?

Transformers are used in a variety of applications, including power transmission, distribution, and conversion. Transformers are also used in audio equipment, such as amplifiers and speakers.

What is the future of transformers?

The future of transformers is likely to be bright. Transformers are a versatile and efficient way to transfer electrical energy. As the demand for electrical energy continues to grow, the demand for transformers is likely to grow as well.

  1. A transformer is a device that:
    (A) transfers energy from one circuit to another
    (B) converts AC power to DC power
    (C) converts DC power to AC power
    (D) increases or decreases the voltage of an AC power source

  2. The primary coil of a transformer is connected to the:
    (A) input AC power source
    (B) output AC power source
    (C) load
    (D) both the input and output AC power sources

  3. The secondary coil of a transformer is connected to the:
    (A) input AC power source
    (B) output AC power source
    (C) load
    (D) both the input and output AC power sources

  4. The turns ratio of a transformer is the ratio of the number of turns in the primary coil to the number of turns in the secondary coil. The turns ratio determines:
    (A) the voltage ratio of the transformer
    (B) the current ratio of the transformer
    (C) both the voltage and current ratios of the transformer
    (D) neither the voltage nor current ratios of the transformer

  5. A step-down transformer is a transformer that:
    (A) increases the voltage of an AC power source
    (B) decreases the voltage of an AC power source
    (C) converts AC power to DC power
    (D) converts DC power to AC power

  6. A step-up transformer is a transformer that:
    (A) increases the voltage of an AC power source
    (B) decreases the voltage of an AC power source
    (C) converts AC power to DC power
    (D) converts DC power to AC power

  7. A transformer is an efficient device, meaning that:
    (A) most of the input power is converted to output power
    (B) most of the input power is lost as heat
    (C) the output power is always less than the input power
    (D) the output power is always greater than the input power

  8. The main advantage of using a transformer is that it:
    (A) allows you to transmit power over long distances
    (B) allows you to change the voltage of an AC power source
    (C) allows you to convert AC power to DC power
    (D) allows you to convert DC power to AC power

  9. The main disadvantage of using a transformer is that:
    (A) it is an inefficient device
    (B) it is a bulky device
    (C) it is a noisy device
    (D) it is an expensive device

  10. Transformers are used in a variety of applications, including:
    (A) power transmission
    (B) power distribution
    (C) electronics
    (D) all of the above

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