What Are Electric Transformers?
Electric Transformers are stationary devices designed to transfer electrical power between circuits, while maintaining the same frequency.
These systems are purpose-built to change voltage levels higher (+) or lower (-) which in turn changes (inversely) the current. The transfer of voltage is based upon principles of electromagnetic induction and mutual induction.
Working Principles Of Electric Transformers
Electric transformers work on the principles put forward by Faraday’s laws of electromagnetic induction. The basic premises includes that electricity produces magnetic fields AND that magnetism produces electricity.
Without a doubt magnetism is one of the most important components of everything in electrical systems. Transformers take advantage of magnetic properties, to change voltage levels either higher or lower.
We manipulate the strength of the magnetic field in the transformer, and through this the electrical force and electrical power changes. In doing this, we sometimes use a conductive wire (as in copper) and as we go through the process we set electrons in motion for electricity transmission.
Transformers will change voltage levels based on the configuration of the coils around their core. While alternating current goes through the transformer, the changing magnetic field creates an electromotive force on the output wire on the core when wired with this changing magnetic field
Electricity needs to be carried at a higher voltage over long distances, or in between power plants for efficient transfer.
Thus, electrical motion becomes hazardous, risking electrical shock, explosion or accidental contact with secondary circuits as the electrical energy attempts to fire through the equipment but is being limited, to the amount that is safe, for human/operational costs.
When electricity reaches a final destination it needs to lower voltage to not destroy, or fry everything it connects to and keep it safe from electrical risk factors.
Sub stations are at the power plants to be able to step down high initial voltage, into safe level three voltage, to transfer from an entire disposal unit. In reality, the power plant has many sub stations that ultimately to step down a lower voltage power supply that suits the design of a business and its equipment’s intended safe use.
Transformers regulate voltage levels to the voltages which are required for all, most, of our home appliances like stoves, air conditioning, computers, heaters, and televisions; in the local residential sense.
Industrially transformers are used to change the voltage to any higher voltage, in the step-up process, so the electrical equipment can tolerate the highest amount of voltage; including a millisecond before the power supply takes the high voltage dangerous levels away from the electrical equipment.
A transformer reduces voltage levels from the amount of wire turns wrapped on the primary to the secondary winding when the primary has to have a higher amount of wire turns as compared to the secondary.
Conversely, A transformer increases voltage levels to where the primary has to have fewer wire turns than the secondary.
It is standard that a transformer has the same number of wire turns; if so the voltage transfer function just passes through the voltage being supplied.
While all transformers have energy loses in one way or the other, just in sole energy conversion from inductance into heat which loss is intended; it is usually hard to cool or lost manage those losses through heat energy since transformers are mainly static, if actual heat exceeds its designed deployment of insulation for the transformer wires eventually it will breakdown insulation; Cooling can be done two ways, air and oil.
Air cooling uses moving air over the coiled wire to take away and dissipate heat energy; ambient air is also taking heat energy from coiled wire moving through air. The other cooling method for the transformer besides air is oil or water immersion.
The core is simply a utilization of the wire (or wire windings) will be connected by a magnetic core material, which is mainly iron or ferrite and the core is usually laminated with conductive copper or enamel coated material.
Parts of Electric Transformers
The electric transformer is made of several parts, which help with the electrical transformer design and performance, these parts will be briefly listed in the sections to follow.
Transformer Core
The core will suspend the primary and secondary winding and provide a low reluctance path for the electromagnetic flux. The core consists of thin sheets of oriented, premium steel separated by insulating material, which helps the core minimize hysteresis and eddy currents.
The steel has less than 0.1 %carbon content and has silicon content that further helps reduce eddy currents. In the case of a three-phase transformer, each of the core’s limbs holds the primary and secondary windings for each phase, which are connected via magnetic yokes.
The core can be constructed in two main types: core type or shell type, in which the core surrounds the windings.
The Transformer Winding
There is a primary and a secondary winding for each transformer phase. The windings consist of multiple turns of copper or aluminum conductors, which are insulated from themselves and the core.
The winding category and configuration is dependent on the current rating, short circuit strength, temperature rise, impedance, and voltage surge.
The winding that is rated for higher voltage is the HV winding, and the one rated for lower voltage is the LV winding.
High voltage windings usually have conductors that are thinner compared to LV windings that are placed closer to the core. Shell type transformers may have their HV windings sandwiched between LV coils, which may be segmented into several pieces.
Core type transformers can have four categories of winding, and the category selected will be based on the current capacity and number of turns.
The Transformer Insulation
Because a transformer can be damaged severely from inadequate insulation, it is one of the most vital considerations in a transformer.
Insulating materials must be chosen to ensure that the insulation provides high dielectric strength, high temperature resistance, and high mechanical properties.
Common insulation materials for transformers include cotton, synthetic textiles, and paper. These materials will be used as insulation between windings, the core, and between active components.
Transformer tanks
The tank has two functions: to protect the core and windings from the environment and store oil. Except for some components and accessories, the tank provides support.
Tanks are typically made from shaped steel plates, though shaped aluminum sheets may instead be used to save weight, despite aluminum being generally more costly than steel.
Transformer oil
In oil-immersed transformers, transformer oil serves several functions that improve performance. It enhances insulation between electrical conducting parts and cooling properties, and helps identify fault locations.
Connections and bushings
In a transformer, terminals are used to connect incoming and outgoing cables. Internal electrical terminals are connected through bushings at the ends of the windings.
Bushings provide a separation between terminals and tank and provide safe passage for electrical conductors connecting the terminals to the windings. Bushing materials can include epoxy resins and porcelain.
Oil conservators
The oil conservator is above the tank and bushings. The conservator contains a rubber bladder to permit for expansion and contraction of oil with changes in temperature. An indicator is attached to the oil conservator to indicate oil level; an oil pipe links the conservator to the main tank.
Electric transformer breather
Breathers provided in oil-immersed transformers allow the oil to remain dry. The expansion and contraction of air in the oil conservator tank occurs as the temperature changes.
The air enters and exits the conservator through a breather that contains silica gel to ensure the air entering the conservator is dew-free.
Cooling: Radiators and fans
Because of the heat generated during the power lost in a transformer, heat generated as a result of power loss must be managed. Dry-type transformers rely on ambient air for cooling; oil- immersed transformers can cool using different methods.
A fan and some radiators might be utilized, based on the power rating, loss in a manufacturer’s room, and cooling requirements of a unit. The cooling process moves heat from the core and windings into the oil in the tank that is dissipated through the radiators.
In larger transformers, forced cooling methods can use cooling radiators to make the heat displacement even more effective.
Emergency Release: Explosion Vent
An explosion vent is designed to relieve the oil and gas buildup in a transformer. The explosion vent is located on the top of the conservator tank.
The vent consists of a metal service pipe with a diaphragm located on top. When the internal oil pressure becomes excessive or unsafe, the diaphragm ruptures, venting the excess pressure to atmosphere safely.
Voltage Regulation – Tap Changers
Tap changers are utilized on the transformer’s secondary voltage, and alter the turns ratio of the second transformer voltage. Tap changers are classified as on-load, and off-load tap changers.
On-load tap changers are used to adjust the system while the current is still flowing. Off-load tap changers are used when the transmission transformers are off-load.
Protection – Buchholz Relay
The Buchholz relay is commonly used in distribution oil immersed transformers with ratings over 500 kVA. This relay monitors currents and voltage, with an additional safe monitoring function for gases resulting from oil decomposition during a short circuit.
When gases are detected, the relay signals an alarm, and trips the circuit breaker to interrupt current flow.
Although the previous discussed common components used in large oil immersed transformers, more components may be used depending on each manufacturers room’s design.
This would include extra protection relays, as well as installation sensors (pressure and temperature), heat exchangers (optimizing cooling), and protection relays.
Types of Electric Transformers
All electric transformers operate as a result of Faraday’s laws of electromagnetic induction, and can be built or classified in different ways to meet a specific application or requirements.
Iron Core Transformers
This type of electric transformer is considered to be a very efficient transformer. Iron core transformers typically consist of many iron plates, all made of materials with excellent magnetic properties.
This type of electric transformer facilitates quick magnetizing and demagnetizing processes. This feature has made them extremely desirable.
The iron plates are normally silicon steel and covered with compliant paint to reduce heat dissipation from operation.
Isolation Transformers
All electric transformers utilize induction and do not rely on a conductive connection with electricity for conversion. Technically speaking, all electric transformers are isolation transformers.
The primary purpose of an isolation transformer is to transfer electrical power from one source to another piece of electrical equipment, while isolating that piece of electrical equipment from the original power source.
Isolation transformers function similarly to the other transformer types, but they are designed specifically to isolate electricity, or the electrical piece of equipment, from the power source.
Uses of isolation transformers include uninterruptible power supplies, robotics, test and measurement systems, motor controls and industrial control panels, data communication systems.
Ferrite Core Transformers
These electric transformers handle loss of energy in an efficient manner in high frequency applications because they use ferrites as cores which are high permeability materials. They have a standard E-type configuration, and can be fitted into various functions or regulated in size.
Step Up Transformers
These transformers are well-suited for applications in power transformation and modification applications because they convert lower voltages to higher voltages, reduce amperage, and the effects of resistance, great.
Both direct and indirect energy transfer occurs at the termination of the transformation process.
In a transformer, the electric energy passes through two sets of coils, with the second set having a higher ratio of windings and they form complete coil assembly Some applications for step-up transformers may have a single set of windings, others may have a second – an extra tertiary set of windings.
All electric transformers have two sets of coils to do these conversions. The coil windings can be used with a core with ferrite material or laminated core and the coils can be copper wire, enamel coated, or bare copper.
Step-up transformers have wire coils from elemental coil sets which include aluminum, nickel, copper, chromium and steel, which can help utility companies be less energy dependant and more energy efficient
High Voltage transformers
The voltage of a power transmission line is a direct indicator of how much power can be passed in a transmission line.
And these High Voltage transformers are used for either changing the volts, usually within high voltage applications, thus giving a low degree of uncertainty for high voltage services or components to high voltage power lines.
high voltage transformers refers to any electric transformer that operates higher than 600 volts and up to 5000 volts, wherein a volt is the measurement of electromotive force.
High Voltage electric transformers have the ability to directly provide direct metering and limitations in high voltage circuit transformers, including over voltage conditions, staff safety and so on.
High Voltage electric transformers can be used to support electrostatic applications in industrial and scientific environments.
Toroidal Core Transformers
A toroidal shape is helping to decrease inductance leakage in the transformer to maintain high inductance being absorbed within the transformer however allows maximum inductance to be utilized on a specific load.
Toroidal transformer construction is based on shorter more compact windings, is lighter and assumes conductively higher inductone or inductive loads on higher rated lower physically rated transformers. Their windings take longer but more costly to manufacture.
Air Coil Transformers
These can be seen from air coils with no magnetic core, air coil transformers are used in radios and small electronic manuals.
The inch of operation is based on flux linkage between two coils which are magnetically coupled coils/ windings known name as primary and secondary coils/ windings.
The transformers create flux from their windings and the ambient air. When winding coils, plastics (especially plastic tubing) and cardboard are used for low magnetic permeability when wrapping the coils.
Laminated Core Transformers
Laminated core transformers appear to use a core made of laminated sheets of iron and nickel. The nickel helps reduce energy losses during energizing windings.
The major advantage of using laminated core transformers is the ability to reduce eddy currents leading to improved energy transfer between the primary coil and the secondary coil.
Pulse Transformers
Pulse transformers are commonly operated on direct current (DC) because their flux density is invariant with time and does not pass through zero. They typically connect load resistance with a pulse power source.
Examples of pulse transformers in use are radar systems, for those of you serving on submarines, where radar transmitters require a high voltage and high impedance. Obviously, anyone using radar would be a source of high voltage in the output with output tubes such as magnetrons.
Small pulse transformers can produce short electrical surges to pass telecommunications and specialty equipment such as camera flashes and radar systems. Medium-sized pulse transformers should be used in applications which requirement electric circuits.
Current Transformers (CT)
Current transformers are good for measuring the flow of electricity in electrical transmission lines. Power transformers have a reason for controlling voltage.
Current transformers are intended for measuring and for monitoring flow of current, for measurement purposes. It is important to understand how these transformers work because current transformers are also used to control the flow of electricity to electric circuitry.
Low Voltage Transformers
Low Voltage transformers are power transformers and are used to change the voltage capacity associated with a low voltage electrical transmission line.
A low voltage transformer is the size that can be held between two fingers and is also much lighter than a high voltage transformer. Most lower voltage transformers simply transfer or change 120 volts to 12 volts or 24 volts.
Automatic Transformers
Automatic transformers are electric transformers that have a single winding. These electric transformers are more cost effective than a conventional power transformer.
In a autotransformer, the TM winding is the primary winding and the TM winding is the secondary winding (and also has craft three taps as electrical connection points).
The advantages of an autotransformer are very compact, good price, very light. The autotransformer is useful in applications with variable and different voltage levels.
Polyphase Transformers
Polyphase transformers have three or more conductors, they can have as many as fifteen phases. Polyphase transformers have multiple windings on both the primary and secondary core. Many Polyphase transformers will use zigzag colored wire, especially when some form of grounding is necessary.
Zig Zag Transformers
Zig Zag Transformers can be used to derive a neutral reference point for underground systems. Zig zag transformers can be used in many industries because they can provide a neutral point for grounding.
The petrochemical and power distribution and automotive industries all utilize the zig zag transformer. Zig zag transformers have a primary winding only but no secondary winding (Although zig zag transformers consist of six windings on three separate cores).
A zig zag transformer has two halves of windings; the only difference is the way that the two halves are interconnected and so there is only one way of winding and connecting the zig zag transformer winding, so there is a difference in connection of the coils and the core.
Three Phase Transformers
A three-phase transformer is arguably the best polyphase transformer to use. It is possible to connect three single-phase transformers to a three-phase system and call it a three-phase transformer.
However, it is a more economical option to utilize a dedicated three-phase transformer. Three-phase transformers have three primary and secondary windings that can be arranged in a generation of configurations, either delta or star, for example, a three-phase delta-delta or star-star.
Three-phase transformers are key and fundamental in directing and controlling electric current when transferring it from the wires, to homes, or businesses.
A current transformer for example controls and turns the current from the electric line to the next areas or equipment to be put in motion.
A transformer that is power connected is generally the most effective method of operating electrical systems and select electrical appliances in a safe manner.
Power Transformers
This type of transformer acts between the grid and the generators; or for energy to get sent to a substation; the size of the transformer needs cooling. It typically uses oil and cooling agents.
It is an expensive system due to its three-phase characteristics. However, it is more advantageous even though the cost of these transformers is higher than single phase systems, they have more capabilities than single phase systems. These transformers are classified into three types based on their voltage specifications.
Distribution Transformer
These transformers act as step down transformers to reduce high voltages to low voltages when electrical energy is carried over two coil sections where the second coil section has less windings.
The amount of power that can be developed if the coil is greater or lesser when compared to geographical area.
Measurement transformer
These transformers are normally used to isolate main power and voltage and convert to a smaller ratio.
Applications of Electric Transformers
Electric transformers play an important daily part in the adjustment of electrical current to be used in any appliance, these transformers control voltage flow while appliances are being charged, allowing a regulated voltage flow to prevent excessive voltage from flowing, without controlled voltage flow appliances can be destroyed by electrical surges.
Electric transformers play an important role in steel production, supplying high voltages for melting and welding, and low current for cooling processes.
They also are important in chemical processing as they are used to supply power for electrical activity during electrolysis, including electroplating of metals like aluminum, copper and zinc.
Transformers control the electrical current allowing for accurate control of whether the electrolysis, electric current is used properly to drive these chemical reactions.
Advantages of Electric Transformers
The electric transformer, in regard to costs, remain the cheapest and most efficient source for transmission and isolation of electrical voltage.
Transformer types provide a great deal of applications; for example, current transformers can be used as step down transformers for measuring devices.
Transformers can be seen as step-up or step-down depending upon the installation. Similar to current transformers, they have multiple taps on the primary winding to change input voltage.
Disadvantages of Electric Transformers
The electric transformer relies on cooling electrical energy is lost as waste energy in the form of heat, high enough to prematurely destroy the insulation on windings. Electric transformers are not designed for DC voltage.
Maintenance is complicated with electrical transformers, because transformers have failure modes such as oil leaks, over spanning and harmonics would lead to degradation and consequential damage.