- Electrical Machines Tutorial
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- Basic Concepts
- Electromechanical Energy Conversion
- Energy Stored in a Magnetic Field
- Singly-Excited and Doubly Excited Systems
- Rotating Electrical Machines
- Faraday’s Laws of Electromagnetic Induction
- Concept of Induced EMF
- Fleming’s Left Hand and Right Hand Rules
- Transformers
- Electrical Transformer
- Construction of Transformer
- EMF Equation of Transformer
- Turns Ratio and Voltage Transformation Ratio
- Ideal and Practical Transformers
- Transformer on DC
- Losses in a Transformer
- Efficiency of Transformer
- Three-Phase Transformer
- Types of Transformers
- DC Machines
- Construction of DC Machines
- Types of DC Machines
- Working Principle of DC Generator
- EMF Equation of DC Generator
- Types of DC Generators
- Working Principle of DC Motor
- Back EMF in DC Motor
- Types of DC Motors
- Losses in DC Machines
- Applications of DC Machines
- Induction Motors
- Introduction to Induction Motor
- Single-Phase Induction Motor
- Three-Phase Induction Motor
- Construction of Three-Phase Induction Motor
- Three-Phase Induction Motor on Load
- Characteristics of 3-Phase Induction Motor
- Speed Regulation and Speed Control
- Methods of Starting 3-Phase Induction Motors
- Synchronous Machines
- Introduction to 3-Phase Synchronous Machines
- Construction of Synchronous Machine
- Working of 3-Phase Alternator
- Armature Reaction in Synchronous Machines
- Output Power of 3-Phase Alternator
- Losses and Efficiency of 3-Phase Alternator
- Working of 3-Phase Synchronous Motor
- Equivalent Circuit and Power Factor of Synchronous Motor
- Power Developed by Synchronous Motor
- Electrical Machines Resources
- Electrical Machines - Quick Guide
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- Electrical Machines - Discussion
Electrical Transformer
In electrical and electronic systems, the electrical transformer is one of the most useful electrical machine. An electrical transformer can increase or decrease the magnitude of alternating voltage or current. It is the major reason behind the widespread use of alternating currents rather than direct current. A transformer does not have any moving part. Therefore, it has very high efficiency up to 99% and very strong and durable construction.
Electrical Transformer
A transformer or electrical transformer is a static AC electrical machine which changes the level of alternating voltage or alternating current without changing in the frequency of the supply.
A typical transformer consists of two windings namely primary winding and secondary winding. These two windings are interlinked by a common magnetic circuit for transferring electrical energy between them.
Principle of Transformer Operation
The operation of the transformer is based on the principle of mutual inductance, which states that when a changing magnetic field of one coil links to another coil, an EMF is induced in the second coil.
When an alternating voltage V1 is applied to the primary winding, an alternating current flows through it and produces an alternating magnetic flux. This changing magnetic flux flows through the core of the transformer and links to the secondary winding. According to Faraday’s law of electromagnetic induction, an EMF E2 is induced in the secondary winding due to the linkage of changing magnetic flux of the primary winding. If the secondary winding circuit is closed by connecting a load, then this induced EMF E2 in the secondary winding causes a secondary current I2 to flow through the load.
Although the changing magnetic flux of primary winding is also linked with the primary winding itself. Hence, an EMF E1 is induced in the primary winding due to its own inductance effect. The value of E1 and E2 can be given by the following formulae,
$$\mathrm{\mathit{E_{\mathrm{1}}}\:=\:-\mathit{N_{\mathrm{1}}}\frac{\mathit{d\phi }}{\mathit{dt}}}$$
$$\mathrm{\mathit{E_{\mathrm{2}}}\:=\:-\mathit{N_{\mathrm{2}}}\frac{\mathit{d\phi }}{\mathit{dt}}}$$
Where N1 and N2 are the number of turns in the primary winding and secondary winding respectively.
On taking the ratio of E2 and E1, we get,
$$\mathrm{\frac{\mathit{E_{\mathrm{2}}}}{\mathit{E_{\mathrm{1}}}}\:=\:\frac{\mathit{N_{\mathrm{2}}}}{\mathit{N_{\mathrm{1}}}}}$$
This expression is known as transformation ratio of the transformer. The transformation ratio depends on the number of turns in primary and secondary windings. Which means the magnitude of output voltage depends on the relative number of turns in primary and secondary windings.
If N2 > N1, then E2 > E1, i.e., the output voltage of the transformer is more than the input voltage, and such a transformer is known as set-up transformer. On the other hand, if N1 > N2, then E1 > E2 i.e., the output voltage is less than input voltage, such a transformer is called step-down transformer.
From the circuit diagram of the transformer, we can see that there is no electrical connection between the primary and secondary instead they are linked with the help of a magnetic field. Thus, a transformer enables us to transfer AC electrical power magnetically from one circuit to another which a change in the voltage and current level.
Important Points
Note the following important points about transformers −
The operation of transformer is based on the principle of electromagnetic induction.
The transformer does not change the frequency, i.e. the frequency of input supply and output supply remains the same.
Transformer is a static electrical machine, which means it does not have any moving part. Hence, it has very high efficiency.
Transformer cannot work with direct current because it is an electromagnetic induction machine.
There is no direct electrical connection between primary and secondary windings. The AC power is transferred from primary to secondary through magnetic flux.
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