There are various types of transformer, each with its own applicable usage. However, the main objective of using them is the same – transforming electrical power from one type to another.
In this blog, we will aim at enlightening the readers about Transformer basics and working principle, types of transformer on the basis of voltage, medium, uses, configuration and place of usage, their advantages and limitations.
A Transformer is an electrical device that can be used to transfer the power from one circuit to another by using the principles of electromagnetic induction. There are two types of winding in the transformer i.e. Primary winding and the secondary winding. Primary winding means a winding to which an AC supply is connected and the secondary winding means a winding to which a load is connected. The voltage will be raised or lowered in a circuit, but with a proportional increase or decrease in the current ratings.
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The transformer working depends upon Faraday's law of electromagnetic induction. According to Faraday's laws,
"The Rate of change of flux linkage with respect to time is directly proportional to the EMF induced in a conductor or coil".Faraday's Law
E= N dϕ /dt
E = Induced EMF
N = the number of turns
dϕ = Change in flux
dt = Change in time
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Transformer can be categorized on the basis of voltage level, medium, uses, configuration and place of usage. Now we will discuss each type in detail.
On the basis of voltage level, transformer types are listed below.
|Based On Voltage Level||Voltage||No. of Turns||Current||Rating of Output Voltage||Uses|
|Step-Up Transformer||Vs > Vp||Np < Ns||Ip > Is||220V - 11kv or above||
Doorbell, voltage converter, etc.
|Step-Down Transformer||Vs < Vp||Np > Ns||Ip < Is||
40-220v, 220-110v, or
110-24v, 20v 10v etc.
(Power plants. X-rays machines, micro-waves, etc.)
|Isolation Transformer||Vs = Vp||Np = Ns||Ip = Is||Output voltage which is identical to their input - known as 1:1 transformers||Safety purpose insulation barrier, to cancel noise|
A Step Up Transformer is a device which converts low voltage at primary side to high voltage at secondary side. The primary winding of a coil has less number of turns than the secondary winding.
Vp/Vs = Ns/Np
A Step Down Transformer is a device which converts high voltage at primary side to low voltage at secondary side. The secondary winding of a coil has less number of turns than the primary winding.
Vs/Vp = Ns/Np
Isolation transformer can be step-up transformer or step-down transformer but the primary and secondary voltage values are always equal i.e. turns ratio is always 1. This is obtained with a same number of turns on the primary and secondary windings. Isolation transformers are referred to as "insulated".
Vs/Vp = Ns/Np Where Ns=Np
On the basis of core medium, transformer types are listed below.
|Based on Core Medium||Core Material||Flux Linkage||Eddy Current Losses||Reluctance||Mutual Inductance||Efficiency||Uses|
|Air-Core Transformer||Non-magnetic strip||Through the air||Low||High||Less||Low||Radio-frequency application|
|Iron Core Transformer||Multiple soft iron plates||Through the iron plate bunch||Large||Less||High||High||Power distribution|
|Ferrite Core Transformer||Ferrite core||Through a window or hole||Very Low||Very Low||Very High||Very High||Switch-mode power sup|
Air-core transformers are designed to transfer radio-frequency currents—i.e., used in radio transmitter and communication devices etc. As the name suggests, these transformers have no solid core, which makes them very light in weight, thus making them ideal for small-sized portable electronic devices. Air core transformers create flux using the windings and the air passing through them. This help air core transformer to completely eliminate undesirable characteristics of ferromagnetic core (eddy current losses, hysteresis, saturation, etc.)
In this type of transformer, primary and secondary windings are wounded on multiple iron plates. These iron plates provide perfect linkage path to the generated flux and serve analogous functions in the audio-frequency range. Iron core transformer are widely used and highly efficient as compare to air core transformer.
Ferrite core transformer means a transformer whose magnetic core is made up of ferrite. Ferrites are non-conductive, ceramic compounds that are ferromagnetic in nature. The high magnetic permeability of these transformers makes them ideal for a variety of high frequency transformers, adjustable inductors, wide band transformers, common Mode Chokes, switched-mode power supply and radio frequency applications.
On the basis of usage, transformer types are listed below.
|Based On Usage||Types of Network||Operating Condition||Load Fluctuations||Winding Conditions||Insulated Level||Designed Efficiency||Application|
|Power Transformers||Transmission network of higher voltages||Always operated at full load||Very Less||Primary winding connected with stars, secondary in delta||High||Maximum efficiency at 100% load||Used in generating stations, and transmission substations|
|Distribution Transformers||Distribution network of lower voltage||Operated at load less than full load as load cycle fluctuates||Very High||Primary winding connected with delta, secondary in stars||Low||Maximum efficiency at 60% to 70% load||Used in distribution stations also for industrial and domestic purposes|
Main principle of power transformer is to convert the Low voltage input to a high voltage output. This transformer acts as a bridge between the power generator and the primary distribution grid. This has complex construction due to high power generation and mainly installed at the generating stations and transmission substations. The power transformers are employed in the transmission networks of higher voltages.
Distribution transformers are step down transformer and used in distribution network for industrial and domestic purpose. These transformers convert High grid voltage to the end customer required voltage where the electrical energy is distributed and utilized at the consumer end. In order to distribute the power from power plant to remote locations, these transformers are used.
On the basis of configuration, transformer types are listed below.
|Based On Electrical Supply||Power Supply||Network||No of Coils||No of Terminals||Voltage||Power Transfer Capability||Efficiency||Uses|
|Single-Phase Transformer||The power supply through one conductor||Simple||2||4||Carry 230v||Minimum||Less||For home appliances|
|Three-Phase Transformer||The power supply through three-conductor||Complicated||6||12||Carry 413v||Maximum||High||
In large industries and for running heavy loads
Power or distribution transformer
When there is only one coil at primary side and one coil at secondary side, then the transformer is called single phase transformer. Here the power supplies through a single conductor. This type of transformer accepts single-phase alternating current and output single-phase alternating current, typically at variant voltage level that operates in a unified time phase. These types of transformer are mostly used in the household devices.
Three phase transformer means the power flows through three conductors. Three phase transformer contains six coils, three coils at primary side and three coils at secondary side. This type of transformer accepts three-phase alternating current and output three-phase alternating current, typically at variant voltage level that operates in a unified time phase. These types of transformer are mostly used as a power or distribution transformers
On the basis of place of usage, transformer types are listed below.
|Based On Place Of Usage||Cooling Medium||Maintenance Cost||Sound Operating Level||Price||Efficiency||Uses|
|Dry-Type Transformers(Indoor)||Air as the cooling medium||Low||Noise pollution exist||Expensive||Less efficient||Public places like transportation hubs and company buildings|
|Oil-filled Transformers(Outdoor)||Oil as the cooling medium||High||No noise pollution||Cheap||More efficient||For outdoor, high rated application|
Indoor transformers are usually a Dry type transformer. These transformers use air as cooling medium and usually their primary and secondary side connections are isolated. Dry type transformers are installed in buildings and close to buildings because they are environmentally safer i.e. less flammable. These type of transformers are considered as ideal for shopping malls, hospitals, residential complexes and other commercial areas.
Outdoor transformers are usually an Oil filled transformers. These transformers use oil as cooling medium and are designed to be utilized in outdoor environments due to the chance of oil leakage and spills that create a fireplace risk, and must be protected against environmental conditions.
This is all about the various types of transformer. We hope that after reading this you would gain some valuable insights and ideas out of this blog. If you still have any question you can comment in the comment section below.
One of AllumiaX's recent initiatives is a corporate sponsorship for the GeneralPAC platform which provides tutorials for power systems protection, automation and controls. Here, you will find the video series of Current Transformers. In this series they will be going over the Introduction to Current TransformersBrief Intro to Current Transformers and its Applications, Current Transformer Equivalent Circuit Model.
About The Author
Abdur Rehman is a professional electrical engineer with more than eight years of experience working with equipment from 208V to 115kV in both the Utility and Industrial & Commercial space. He has a particular focus on Power Systems Protection & Engineering Studies.