What is the transformer?
A
transformer is an electromagnetic device that changes (or converts) AC
electrical energy at one voltage level into electrical energy at another
voltage level, at the same frequency, through the action of a magnetic field.
Types of Construction
The
primary and secondary windings are wrapped one on top of the other with the
low-voltage winding innermost, due to 2 purposes:
- It simplifies the problem of insulating the high-voltage winding from the core.
- It results in much less leakage flux
Types of Transformers and Their
Applications
1.
Based on the Voltage Level
- Step-Up Transformer
- Increases voltage from the
primary to the secondary winding.
- Applications: Power transmission in
electrical grids (e.g., stepping up voltage at power stations).
- Step-Down Transformer
- Decreases voltage from the
primary to the secondary winding.
- Applications: Used in distribution
networks and household appliances (e.g., charging adapters, power
supplies).
2.
Based on Core Material
- Iron Core Transformer
- Uses laminated iron as the
core to minimize energy losses.
- Applications: Power distribution and
electrical applications requiring high efficiency.
- Air Core Transformer
- Uses an air gap instead of an
iron core, reducing eddy current losses.
- Applications: High-frequency applications
like radio transmitters and wireless charging.
3.
Based on the Number of Phases
- Single-Phase Transformer
- Works with single-phase AC
circuits.
- Applications: Domestic appliances,
lighting, and small industrial loads.
- Three-Phase Transformer
- Designed for three-phase
power systems, offering efficient energy transfer.
- Applications: Used in industrial plants,
power grids, and large motors.
4.
Based on Functionality
- Isolation Transformer
- Provides electrical isolation
between primary and secondary circuits without changing the voltage.
- Applications: Safety applications,
medical equipment, and sensitive electronic devices.
- Autotransformer
- Has a single winding that
acts as both primary and secondary, with a variable voltage output.
- Applications: Used in voltage regulators,
stabilizers, and AC motors.
- Instrument Transformer
- Used for measurement and
protection in electrical systems.
- Types:
- Current Transformer (CT) – Measures high currents
safely.
- Potential Transformer (PT) – Measures high voltages
accurately.
- Applications: Power system monitoring, metering, and protection.
Ideal Transformer with Load
- Voltage Ratio: The primary and secondary voltages follow the ratio
- Current Ratio: The primary and secondary
currents follow the inverse ratio
- Power Conservation:
- Instantaneous power input to
the primary = Instantaneous power output from the secondary
Impedance
Transformation
- Secondary Load Impedance: Defined as
- Apparent Impedance at the Primary: The impedance at the primary is transformed based on the square of the turns ratio
, Where 
Cooling systems
in transformers
• Cooling of transformers is very important to
ensure efficient operation, prevent overheating, and maintain durability.
• Transformers can be classified into different types based on the cooling method used.
Classification
of Transformers Based on Cooling Medium
The image categorizes transformers based on their cooling methods:
|
Dry-Type
Transformers |
Oil-Immersed
Transformers |
Subtypes
of Oil-Immersed Transformers |
|
o
Do not
use any liquid (like oil) for cooling or insulation. o
Heat is
dissipated through air convection or forced air. o
Suitable for low- and
medium-power applications |
o
Use transformer
oil as a cooling and insulating medium. o
Provide
better cooling efficiency. o
Widely
used for high-power applications. |
Hermetically Sealed Type o
No
conservator tank is used. o
The oil
volume remains constant as the transformer is sealed. Conservator Type o
Equipped
with a conservator tank to handle oil expansion and contraction. o
Helps
maintain oil pressure within the transformer. |
Common Cooling Systems
•
Oil circulates naturally due to thermal convection.
•
Heat is dissipated into the surrounding air via
radiators.
•
Commonly used in small and medium power
transformers.
•
Oil circulates naturally, but external fans blow
air over radiators to enhance cooling.
•
Suitable for transformers with moderate power
ratings.
•
Oil is pumped through the system, and fans blow air
across radiators.
• Increases cooling efficiency for high-power transformers.
•
Oil
circulates naturally, and heat is transferred to water via heat exchangers.
• Requires a water-cooling system and is used in environments where water is readily available.
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