Electrical Engineering
Part-2
Part-2
🔷 Transformers: Working, Types, Losses & Applications
🔷 Introduction
A transformer is one of the most important electrical devices used in power systems. It plays a crucial role in transmitting electrical energy efficiently from one voltage level to another.
In real-world engineering—especially in building services and MEP projects—transformers are widely used for power distribution, load management, and safety.
A transformer is one of the most important electrical devices used in power systems. It plays a crucial role in transmitting electrical energy efficiently from one voltage level to another.
In real-world engineering—especially in building services and MEP projects—transformers are widely used for power distribution, load management, and safety.
🔷 What is a Transformer?
A transformer is a static electrical device that transfers electrical energy between two or more circuits through electromagnetic induction, without changing the frequency.
👉 Main function:
Step up voltage
Step down voltage
A transformer is a static electrical device that transfers electrical energy between two or more circuits through electromagnetic induction, without changing the frequency.
👉 Main function:
Step up voltage
Step down voltage
🔷 Basic Construction of Transformer
A transformer mainly consists of:
A transformer mainly consists of:
🔸 1. Core
Made of laminated silicon steel
Provides a path for magnetic flux
Reduces energy losses
🔸 2. Windings
There are two types of windings:
Primary Winding → Connected to supply
Secondary Winding → Connected to load
There are two types of windings:
Primary Winding → Connected to supply
Secondary Winding → Connected to load
🔸 3. Insulation
Separates windings
Prevents short circuits
Ensures safety
🔷 Working Principle
A transformer works on the principle of electromagnetic induction.
👉 When AC supply is given to the primary winding:
-
Alternating current produces a magnetic field
-
Magnetic flux flows through the core
-
Flux links with secondary winding
-
Voltage is induced in secondary
👉 Formula:
V1 / V2 = N1 / N2
Where:
V = Voltage
N = Number of turns
A transformer works on the principle of electromagnetic induction.
👉 When AC supply is given to the primary winding:
-
Alternating current produces a magnetic field
-
Magnetic flux flows through the core
-
Flux links with secondary winding
-
Voltage is induced in secondary
👉 Formula:
V1 / V2 = N1 / N2
Where:
V = Voltage
N = Number of turns
🔷 Types of Transformers
🔸 1. Step-Up Transformer
Increases voltage
Decreases current
👉 Used in transmission systems
👉 Used in transmission systems
🔸 2. Step-Down Transformer
Decreases voltage
Increases current
👉 Used in distribution (e.g., 11kV to 415V)
👉 Used in distribution (e.g., 11kV to 415V)
🔸 3. Distribution Transformer
Used near load centers
Supplies power to buildings
👉 Common in residential areas
👉 Common in residential areas
🔸 4. Power Transformer
Used in transmission networks
Handles large loads
🔸 5. Instrument Transformer
Used for measurement and protection
Types:
Current Transformer (CT)
Potential Transformer (PT)
Types:
Current Transformer (CT)
Potential Transformer (PT)
🔷 Transformer Losses
Losses reduce efficiency and must be minimized.
Losses reduce efficiency and must be minimized.
🔸 1. Core Loss (Iron Loss)
Due to hysteresis and eddy currents
Occurs in core
🔸 2. Copper Loss
Due to resistance of windings
Depends on load
👉 Formula:
Copper Loss = I²R
👉 Formula:
Copper Loss = I²R
🔸 3. Leakage Loss
Due to leakage flux
Not linking both windings
🔷 Efficiency of Transformer
Efficiency is the ratio of output power to input power.
👉 Formula:
Efficiency = (Output Power / Input Power) × 100
✔ High efficiency (usually 95–99%)
✔ Maximum efficiency when copper loss = iron loss
Efficiency is the ratio of output power to input power.
👉 Formula:
Efficiency = (Output Power / Input Power) × 100
✔ High efficiency (usually 95–99%)
✔ Maximum efficiency when copper loss = iron loss
🔷 Cooling of Transformer
Transformers generate heat, so cooling is necessary.
Transformers generate heat, so cooling is necessary.
🔸 Methods:
Air Cooling (small transformers)
Oil Cooling (large transformers)
Forced cooling systems
👉 Transformer oil:
Provides insulation
Helps in heat dissipation
👉 Transformer oil:
Provides insulation
Helps in heat dissipation
🔷 Transformer Rating
Transformer capacity is rated in kVA, not kW.
👉 Reason:
Power factor varies with load.
Transformer capacity is rated in kVA, not kW.
👉 Reason:
Power factor varies with load.
🔷 Applications in MEP Projects
As a site engineer, you will use transformers in:
✔ Building electrical distribution
✔ Substations
✔ DG set synchronization
✔ HVAC systems
✔ Lift and fire systems
As a site engineer, you will use transformers in:
✔ Building electrical distribution
✔ Substations
✔ DG set synchronization
✔ HVAC systems
✔ Lift and fire systems
🔷 Installation Guidelines (Practical)
✔ Proper earthing must be provided
✔ Ensure adequate ventilation
✔ Maintain safe clearance
✔ Check oil level regularly
✔ Use proper cable sizing
✔ Proper earthing must be provided
✔ Ensure adequate ventilation
✔ Maintain safe clearance
✔ Check oil level regularly
✔ Use proper cable sizing
🔷 Common Problems in Transformers
❌ Overheating
❌ Oil leakage
❌ Insulation failure
❌ Overloading
👉 Regular maintenance is essential
❌ Overheating
❌ Oil leakage
❌ Insulation failure
❌ Overloading
👉 Regular maintenance is essential
🔷 Safety Precautions
✔ Always isolate supply before maintenance
✔ Use protective equipment
✔ Avoid overloading
✔ Ensure proper grounding
✔ Always isolate supply before maintenance
✔ Use protective equipment
✔ Avoid overloading
✔ Ensure proper grounding
🔷 Conclusion
Transformers are a vital part of electrical systems, enabling efficient transmission and safe utilization of electrical energy. A strong understanding of their working, types, and losses helps engineers ensure reliable and efficient operation in real-world applications.
Transformers are a vital part of electrical systems, enabling efficient transmission and safe utilization of electrical energy. A strong understanding of their working, types, and losses helps engineers ensure reliable and efficient operation in real-world applications.
🔷 Electrical Machines (Basics, Types & Working)
🔷 Introduction
Electrical machines are devices that convert electrical energy into mechanical energy or vice versa. In practical engineering, especially in buildings, industries, and infrastructure projects, electrical machines such as motors are widely used.
Understanding electrical machines is essential for installation, operation, and maintenance of systems like pumps, HVAC, lifts, and industrial equipment.
Electrical machines are devices that convert electrical energy into mechanical energy or vice versa. In practical engineering, especially in buildings, industries, and infrastructure projects, electrical machines such as motors are widely used.
Understanding electrical machines is essential for installation, operation, and maintenance of systems like pumps, HVAC, lifts, and industrial equipment.
🔷 What are Electrical Machines?
Electrical machines are devices that operate on electromagnetic principles to convert energy.
👉 Two main categories:
Electrical to Mechanical → Motors
Mechanical to Electrical → Generators
Electrical machines are devices that operate on electromagnetic principles to convert energy.
👉 Two main categories:
Electrical to Mechanical → Motors
Mechanical to Electrical → Generators
🔷 Types of Electrical Machines
🔸 1. Motor
Converts electrical energy into mechanical energy.
👉 Example:
Fans, Pumps, Compressors
Converts electrical energy into mechanical energy.
👉 Example:
Fans, Pumps, Compressors
🔸 2. Generator
Converts mechanical energy into electrical energy.
👉 Example:
DG Set, Power plants
Converts mechanical energy into electrical energy.
👉 Example:
DG Set, Power plants
🔷 What is an Electric Motor?
An electric motor is a machine that converts electrical energy into mechanical rotation.
👉 Working principle:
A current-carrying conductor placed in a magnetic field experiences a force.
An electric motor is a machine that converts electrical energy into mechanical rotation.
👉 Working principle:
A current-carrying conductor placed in a magnetic field experiences a force.
🔷 Types of Motors
🔸 1. AC Motors
These operate on alternating current supply.
These operate on alternating current supply.
🔹 (a) Induction Motor
Most commonly used motor in industries.
👉 Features:
✔ Simple construction
✔ Low cost
✔ High reliability
👉 Types:
Single-phase motor
Three-phase motor
👉 Applications:
Pumps, Fans, Compressors
Most commonly used motor in industries.
👉 Features:
✔ Simple construction
✔ Low cost
✔ High reliability
👉 Types:
Single-phase motor
Three-phase motor
👉 Applications:
Pumps, Fans, Compressors
🔹 (b) Synchronous Motor
Runs at constant speed.
👉 Features:
✔ Constant speed
✔ Used for power factor correction
👉 Applications:
Industrial plants, Power systems
Runs at constant speed.
👉 Features:
✔ Constant speed
✔ Used for power factor correction
👉 Applications:
Industrial plants, Power systems
🔸 2. DC Motors
Operate on direct current.
👉 Types:
Series motor
Shunt motor
Compound motor
👉 Features:
✔ High starting torque
✔ Speed control possible
👉 Applications:
Electric vehicles, Cranes, Lifts
Operate on direct current.
👉 Types:
Series motor
Shunt motor
Compound motor
👉 Features:
✔ High starting torque
✔ Speed control possible
👉 Applications:
Electric vehicles, Cranes, Lifts
🔷 Construction of Induction Motor
🔸 Main Parts
1. Stator
Stationary part
Produces rotating magnetic field
2. Rotor
Rotating part
Produces mechanical output
3. Air Gap
Space between stator and rotor
🔷 Working of Induction Motor
-
AC supply is given to stator
-
Rotating magnetic field is produced
-
Magnetic field cuts rotor conductors
-
Current is induced in rotor
-
Rotor starts rotating
👉 This is called electromagnetic induction
-
AC supply is given to stator
-
Rotating magnetic field is produced
-
Magnetic field cuts rotor conductors
-
Current is induced in rotor
-
Rotor starts rotating
👉 This is called electromagnetic induction
🔷 Slip in Induction Motor
Slip is the difference between synchronous speed and actual rotor speed.
👉 Formula:
Slip = (Ns - Nr) / Ns
Where:
Ns = Synchronous speed
Nr = Rotor speed
Slip is the difference between synchronous speed and actual rotor speed.
👉 Formula:
Slip = (Ns - Nr) / Ns
Where:
Ns = Synchronous speed
Nr = Rotor speed
🔷 Starting Methods of Motor
🔸 1. Direct-On-Line (DOL) Starter
Simple method
High starting current
🔸 2. Star-Delta Starter
Reduces starting current
Used for large motors
🔸 3. Soft Starter / VFD
Smooth starting
Energy efficient
👉 Best for modern systems
👉 Best for modern systems
🔷 Motor Rating
Motor rating is given in:
kW or HP
Voltage
Current
RPM
👉 Example:
5 HP, 415V, 3 Phase Motor
Motor rating is given in:
kW or HP
Voltage
Current
RPM
👉 Example:
5 HP, 415V, 3 Phase Motor
🔷 Losses in Motor
🔸 1. Copper Loss
Due to winding resistance
Due to winding resistance
🔸 2. Core Loss
Due to magnetic effects
Due to magnetic effects
🔸 3. Mechanical Loss
Due to friction and windage
Due to friction and windage
🔷 Efficiency of Motor
👉 Formula:
Efficiency = Output Power / Input Power × 100
✔ High efficiency reduces energy consumption
👉 Formula:
Efficiency = Output Power / Input Power × 100
✔ High efficiency reduces energy consumption
🔷 Applications in MEP Projects
As a site engineer, motors are used in:
✔ Water pumps
✔ HVAC systems
✔ Lifts and escalators
✔ Fire fighting systems
✔ STP/ETP plants
As a site engineer, motors are used in:
✔ Water pumps
✔ HVAC systems
✔ Lifts and escalators
✔ Fire fighting systems
✔ STP/ETP plants
🔷 Practical Tips (Very Important)
✔ Always check motor rating before installation
✔ Ensure proper earthing
✔ Use correct cable size
✔ Provide overload protection
✔ Check rotation direction
✔ Always check motor rating before installation
✔ Ensure proper earthing
✔ Use correct cable size
✔ Provide overload protection
✔ Check rotation direction
🔷 Common Problems
❌ Overheating
❌ Overloading
❌ Voltage fluctuation
❌ Bearing failure
❌ Overheating
❌ Overloading
❌ Voltage fluctuation
❌ Bearing failure
🔷 Maintenance Tips
✔ Regular inspection
✔ Lubrication of bearings
✔ Check insulation resistance
✔ Clean dust and dirt
✔ Regular inspection
✔ Lubrication of bearings
✔ Check insulation resistance
✔ Clean dust and dirt
🔷 Conclusion
Electrical machines, especially motors, are the backbone of modern electrical systems. Understanding their working, types, and applications helps engineers ensure efficient operation and proper maintenance in real-world projects.
Electrical machines, especially motors, are the backbone of modern electrical systems. Understanding their working, types, and applications helps engineers ensure efficient operation and proper maintenance in real-world projects.
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