33 Prerequisite-3_-Comprehensive-Electrical-Engineering-Fundamentals.pptx.pdf

Electric vehicle fundamental

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Prerequisite 3:
Comprehensive Electrical
Engineering Fundamentals

2. Agenda
04 Power Electronic Devices
02 Synchronous Machines
03Electrical Machine Losses
05
Voltage and Current
in Electrical Machines
06 DC Machine Speed Control
Slip in Induction Machine01

3. Slip in Induction Machine

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Induction machines, also known as asynchronous motors, are one of the most common types of electric
motors used in various industrial and domestic applications. They operate on the principle of
electromagnetic induction.
Slip in Induction Machine
Induction Machines

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Slip in Induction Machine
Slip in induction machine is a crucial concept that describes the relative speed difference between the
rotating magnetic field produced by the stator (the stationary part) and the rotor (the rotating part) of the
motor. This difference in speed is necessary for the induction machine to generate torque and operate as a
motor.
Slip in Induction Machines

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Slip in Induction Machine
When an AC voltage is applied to the stator windings of an induction motor, it generates a rotating magnetic
field. This rotating field induces voltage and current in the rotor windings, which, in turn, create a magnetic field
in the rotor. The interaction between these magnetic fields results in the generation of mechanical torque,
causing the rotor to rotate.

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●The rotor speed does not perfectly
match the speed of the rotating
magnetic field in the stator due to
factors such as load conditions and
electrical losses.
●This speed difference is precisely
what slip quantifies.
●It is typically expressed as a
percentage or a fraction.
Where:

●s is the slip (expressed as a decimal or
percentage).
●Ns is the synchronous speed of the rotating
magnetic field in revolutions per minute
(RPM).
●Nr is the rotor speed in RPM.
The slip of an induction motor can be calculated using
the following formula:
Slip in Induction Machine

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Implications of Slip
●Speed Control: By varying the slip, it is possible to control the speed of the motor. A higher slip results in
lower rotor speed and, consequently, a slower motor.
●Torque Production: Slip is directly related to the torque produced by the motor. Higher slip generally
leads to higher torque output, making induction motors well-suited for applications requiring high
starting torque.
●Efficiency: Higher slip corresponds to lower motor efficiency since a significant portion of electrical power
is dissipated as heat due to the slip-induced rotor current.
●Stability: Monitoring and controlling slip is essential for maintaining stable and reliable motor operation,
especially under varying load conditions.
Slip in Induction Machine

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Significance of SlipSlip (S)Rotor Speed (N)
Synchronous Speed
(Ns)
Slip is typically expressed as a percentage and plays a fundamental role in the performance
and behavior of induction motors.
Slip in Induction Machine

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●The synchronous speed (Ns)
of an induction motor is the
theoretical speed at which
the rotating magnetic field
produced by the stator
rotates.
●It is directly related to the
frequency (f) of the power
supply and the number of
poles (P) in the motor.
The formula for synchronous speed is:
Ns = 120 * f / P
Where:
●Ns is the synchronous speed in
revolutions per minute (RPM).
●f is the frequency of the power supply
in hertz (Hz).
●P is the number of motor poles.
Slip in Induction Machine
Synchronous Speed (Ns)

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Rotor Speed
The rotor speed is the actual speed
at which the rotor of the motor
turns. This speed is always slightly
less than the synchronous speed
because of slip.
Slip in Induction Machine
Rotor Speed (N)

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Slip is defined as the difference
between the synchronous speed
(Ns) and the rotor speed (N),
divided by the synchronous
speed.
It is usually expressed as a percentage:
S = ((Ns - N) / Ns) * 100%

Where:
●S is the slip in percentage.
●Ns is the synchronous speed.
●N is the rotor speed.

Slip in Induction Machine
Slip (S)

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Slip is essential for the operation of
induction motors.
Without slip, there would be no
relative motion between the
stator's rotating magnetic field and
the rotor, and therefore, no
induction of current in the rotor
windings.
Slip is required for the following reasons:
●Induction of Current
●Start-up
●Load Variation

Slip in Induction Machine
Significance of Slip

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Induction of Current: The difference in speed between the stator and rotor creates a relative motion, which
induces current in the rotor windings. This induced current generates a magnetic field in the rotor that
interacts with the stator's magnetic field, producing the motor's torque.
Start-up: During motor startup, the rotor is stationary, and the slip is at its maximum (usually around 100%). As
the motor accelerates, slip decreases, and the motor approaches its rated speed.
Load Variation: Slip also varies with changes in load. As the mechanical load on the motor increases, the slip
increases, allowing the motor to deliver more torque to overcome the load.
Significance of Slip
Slip in Induction Machine

15. Synchronous Machines

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Synchronous Machines
●Synchronous machines are a type of
alternating current (AC) electrical machine
that operates synchronously with the
frequency of the power supply.
●These machines come in two main forms:
synchronous generators (alternators) and
synchronous motors.
●They are widely used in power generation
and industrial applications for their ability to
maintain a constant speed and for their role
in maintaining power system stability.
Operation of Synchronous Machine

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Field Winding
Control
Synchronizing
with the Grid
Operation as a
Motor
Operation as a
Generator
Synchronous
Speed (Ns)
The operation of synchronous machines involves the following key points:
Synchronous Machines

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The synchronous speed of a synchronous
machine is determined by the frequency (f)
of the power supply and the number of poles
(P) in the machine.
Synchronous Machines
The formula for synchronous speed is:
Ns = 120 * f / P
Where:
●Ns is the synchronous speed in
revolutions per minute (RPM).
●f is the frequency of the power
supply in hertz (Hz).
●P is the number of motor poles.
Synchronous Speed (Ns)

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When a synchronous machine is operated as
a generator, it is connected to a prime mover
(such as a steam turbine or a diesel engine)
that provides mechanical energy.
The machine converts this mechanical energy
into electrical energy, and its output voltage
and frequency are synchronized with the
power system to which it is connected.
Synchronous Machines





Diesel Engine
Operation as a Generator

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Synchronous Motor
In motor mode, a synchronous machine is
supplied with electrical energy and rotates at
a constant speed. Synchronous motors are
used in applications where maintaining a
precise speed is essential, such as in
industrial processes and large machinery.
Synchronous Machines
Operation as a Motor

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Synchronous Generators
Synchronous generators are crucial for
power generation because they can be
synchronized with the electrical grid's
frequency. This synchronization ensures that
the generated power is in phase with the
grid, making it possible to feed electricity
into the grid and maintain grid stability.
Synchronous Machines
Synchronizing with the Grid

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Synchronous Machines
Synchronous machines have a field winding
on the rotor that allows control of the
machine's power factor and reactive power
output. By adjusting the field excitation, the
machine's reactive power output can be
controlled to support the power system's
voltage stability.
Synchronous Machines
Field Winding Control

23. Electrical Machine Losses

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Electrical Machine Losses
Electrical machine losses refer to the energy that is converted into heat and lost within an electrical machine
during its operation. These losses reduce the overall efficiency of the machine, as they represent energy that
does not contribute to the machine's intended output but instead dissipates as heat.

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Brush and Commutator
Losses
Dielectric
Losses
Stray Load
Losses
Mechanical
Losses
Iron Losses
(Core Losses)
Copper Losses
(I²R Losses)
The operation of synchronous machines involves the following key points:
Synchronous Machines

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Copper Losses (I²R Losses)
●Copper losses occur due to the resistance of
the electrical conductors (usually copper
wires or windings) within the machine.
When current flows through these
conductors, some of the electrical energy is
converted into heat due to the resistance of
the material.
●Copper losses are directly proportional to
the square of the current (I²) flowing
through the conductors and are significant
at higher current levels.
Synchronous Machines
Copper Losses (I²R Losses)

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Iron Losses (Core Losses)
Iron losses, also known as core losses or
magnetic losses, occur in the iron core
of the machine due to the cyclic
magnetization and demagnetization of
the core material as the magnetic field
alternates.
Synchronous Machines
Iron Losses (Core Losses)

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Hysteresis Losses
Synchronous Machines
Hysteresis Losses: These losses occur because the
core material has a finite magnetic hysteresis loop.
Energy is dissipated as the core magnetizes and
demagnetizes with each cycle of the alternating
current.

Eddy Current Losses: Eddy currents are circulating
currents induced in the core material due to the
changing magnetic field. These currents encounter
resistance within the core, leading to energy losses
in the form of heat.
Iron losses consist of two main components

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Mechanical losses, also known as
mechanical energy losses or mechanical
power losses, refer to the energy
dissipated or lost in the form of heat
due to various frictional and resistance
forces within mechanical systems

These losses occur when mechanical
components interact and move relative
to each other, converting some of the
input mechanical energy into thermal
energy.
Synchronous Machines
Mechanical Losses

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Synchronous Machines
Friction Losses: These losses are associated with
the friction between bearings, shafts, and other
moving components. Lubrication can help reduce
friction losses.

Windage Losses: Windage losses result from air
resistance encountered by rotating components,
such as the rotor or fan blades.
Mechanical losses occur within the moving parts of the machine and include:

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Stray Load Losses
Stray load losses occur due to the leakage of
magnetic flux in the machine. This results
from imperfect magnetic coupling between
different parts of the machine, leading to
energy losses in the form of heat.
Synchronous Machines
Stray Load Losses

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Dielectric losses occur in the insulation
materials used within the machine. While
these losses are typically small, they can
become significant in high-voltage
applications. Dielectric losses result from the
resistance of insulating materials to the flow
of electric current.
Synchronous Machines





Dielectric Losses
Dielectric Losses

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In direct current (DC) machines, additional
losses occur at the interface between the
brushes and the commutator. These losses
result from the electrical contact resistance
and friction between the brushes and the
commutator segments.
Synchronous Machines
Brush and Commutator Losses





Brush and Commutator Losses

34. Power Electronic Devices

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Power Electronic Devices
Power electronic devices are semiconductor devices designed for controlling and converting electrical power.
They play a crucial role in various applications, such as motor drives, voltage regulation, power conversion, and
energy management.

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Power DiodesPower TransistorsMOSFETsIGBTs
Some common types of power electronic devices include IGBTs, MOSFETs, power transistors, and power
diodes.
Power Electronic Devices

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IGBTs
●Insulated Gate Bipolar Transistor (IGBT) is a
semiconductor device that combines the
features of both the MOSFET
(Metal-Oxide-Semiconductor Field-Effect
Transistor) and the BJT (Bipolar Junction
Transistor).
●It is widely used in various high-power
electronic applications, such as motor drives,
power inverters, and induction heating systems,
due to its high efficiency and fast switching
capabilities.
Power Electronic Devices
Insulated Gate Bipolar Transistor (IGBT)

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An IGBT consists of three main layers - P-type (positive), N-type (negative), and a thin layer of insulating material
(oxide) between them. It also has a gate terminal, which is used to control the flow of current between the
collector and the emitter.
Structure and Working Principle
Power Electronic Devices

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IGBTs
●Collector: The collector is the layer of the
IGBT that carries the current. It is typically
made of N-type semiconductor material.
●Emitter: The emitter is made of P-type
semiconductor material and is responsible
for emitting the current out of the device.
●Gate: The gate is separated from the
collector-emitter path by the insulating oxide
layer. By applying a voltage at the gate
terminal, the conductivity between the
collector and emitter can be controlled.
Structure and Working Principle
Power Electronic Devices

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Structure and Working Principle
Power Electronic Devices
When a voltage is applied to the gate terminal, it creates an electric field across the insulating layer. This field
allows or blocks the flow of current between the collector and the emitter. When a positive voltage is applied to
the gate relative to the emitter, it repels the holes (P-type charge carriers) in the channel under the gate,
allowing electrons (N-type charge carriers) to flow from the collector to the emitter. This is known as the "on"
state, and the IGBT conducts current.

Conversely, when a negative voltage is applied to the gate relative to the emitter, it attracts the holes in the
channel, effectively blocking the flow of electrons. This is the "off" state, where the IGBT does not conduct
current.

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Example: Controlling an Electric Motor Using an IGBT-Based Inverter Circuit.
Power Electronic Devices
In this scenario, an IGBT-based inverter adjusts an electric motor's speed by rapidly switching IGBTs on and off,
creating a pulse-width modulated (PWM) waveform. Varying the waveform's duty cycle controls the motor's
voltage and speed. When IGBTs are "on," the motor runs; when "off," it slows. This precise control is crucial,
especially in electric vehicles, optimizing energy use. IGBTs are vital in power electronics, ensuring efficient
high-power device control in diverse applications.

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●High Voltage and Current Handling: IGBTs can handle high voltages and currents, making them suitable for
high-power applications.
●Fast Switching Speeds: They can switch on and off rapidly, allowing for precise control over the connected
device.
●High Efficiency: IGBTs have low conduction losses, leading to high efficiency in power conversion
applications.
●Simple Drive Requirements: The input signals required to drive IGBTs are relatively simple, enhancing their
ease of use.
●Modulation Capabilities: IGBTs can be modulated using techniques like PWM to control the average power
delivered to a load.
Advantages of IGBTs
Power Electronic Devices

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●Electric Vehicles: IGBTs are essential in electric vehicles for motor drives and power inverters. As the
automotive industry shifts toward electric vehicles, the demand for high-performance IGBTs is expected to
rise.
●Wide Bandgap (WBG) Semiconductors: Silicon Carbide (SiC) and Gallium Nitride (GaN) are emerging as
alternatives to traditional silicon IGBTs. WBG materials offer higher efficiency and can operate at higher
temperatures.
●Smart Grids and Renewable Energy: With the rise of renewable energy sources like solar and wind, IGBTs
will continue to play a vital role in converting and controlling the generated power for grid integration.
Future Trends
Power Electronic Devices

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MOSFET
MOSFET, or Metal-Oxide-Semiconductor
Field-Effect Transistor, is a fundamental type of
transistor used in electronic devices. It's a
three-terminal semiconductor device that can be
used for amplification and switching electronic
signals.
Power Electronic Devices
MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor)

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●Gate (G): The gate terminal controls the flow of current between the source and drain terminals. It is
separated from the semiconductor material by a thin insulating layer, usually made of silicon dioxide (SiO2).
●Source (S): The source terminal is the source of the charge carriers (either electrons for N-channel MOSFET
or holes for P-channel MOSFET) that flow through the MOSFET.
●Drain (D): The drain terminal is where the charge carriers exit the MOSFET, forming the output of the
device.
A MOSFET has three main components:
Power Electronic Devices

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P-Channel
MOSFET
N-Channel
MOSFET
Working Principle
Power Electronic Devices
The operation of a MOSFET is based on the control of an electric field in a semiconductor device. There are two
main types of MOSFETs: N-channel and P-channel, referring to the type of charge carriers (electrons or holes)
they use.

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●When a positive voltage is applied to the gate relative to the source (G > S), it creates an electric field that
attracts electrons towards the interface between the semiconductor material (usually silicon) and the
insulating layer (oxide).
●This electric field forms a conductive channel between the source and drain, allowing current to flow when
a voltage is applied between the drain and source (D > S).
●When the gate-source voltage is zero or negative, the channel closes, and no significant current flows
between the source and drain.
N-Channel MOSFET
Power Electronic Devices

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●When a negative voltage is applied to the gate relative to the source (G < S), it creates an electric field that
repels holes in the semiconductor material.
●This repulsion forms a conductive channel between the source and drain, allowing current to flow when a
voltage is applied between the drain and source (D < S).
●When the gate-source voltage is zero or positive, the channel closes, and no significant current flows
between the source and drain.
P-Channel MOSFET
Power Electronic Devices

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●Amplification: In electronic circuits to amplify signals.
●Switching: Controlling high-power devices like motors and lights.
●Memory Cells: In integrated circuits as memory cells in RAM (Random Access Memory).
●Signal Processing: In analog and digital signal processing circuits.
MOSFETs are widely used in various applications:
Power Electronic Devices

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Power Transistor
A power transistor, often referred to as a power
bipolar junction transistor (BJT), is a type of
semiconductor device designed to handle high
currents and voltages in various electronic
circuits.


Power Electronic Devices
Power Transistor

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●Emitter (E): The emitter is the region where current carriers (electrons for NPN transistors or holes for PNP
transistors) are injected into the transistor.
●Base (B): The base controls the flow of current carriers between the emitter and collector. By varying the
base current, the transistor can be turned on and off, allowing or restricting the flow of current between
the collector and emitter.
●Collector (C): The collector is responsible for collecting the majority charge carriers (electrons for NPN
transistors or holes for PNP transistors) and passing them to the external circuit.
Structure
Power Electronic Devices

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Working Principle
Power transistors operate on the same basic principles as regular transistors but are specifically designed to
handle high power levels. When a small current flows into the base terminal, it controls a much larger current
flowing between the collector and emitter. This amplification effect is crucial in various applications where a
small input signal needs to control a larger output signal.
Power Electronic Devices

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PNP Power
Transistor
NPN Power
Transistor
Types of Power Transistors
Power Electronic Devices

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NPN Power Transistor
In NPN transistors, the current
flows from the collector to the
emitter when a positive voltage
is applied to the base relative to
the emitter.
Power Electronic Devices
NPN Power Transistor

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PNP Power Transistor
In PNP transistors, the current
flows from the emitter to the
collector when a negative voltage
is applied to the base relative to
the emitter.
Power Electronic Devices
PNP Power Transistor

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●Collector Current (IC): The maximum current a power transistor can handle without being damaged.
●Collector-Emitter Voltage (VCEO): The maximum voltage that can be applied between the collector and
emitter without breaking down the transistor.
●Switching Speed: Power transistors have slower switching speeds compared to other types of transistors,
such as MOSFETs, due to their construction.
Characteristics
Power Electronic Devices

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Power transistors find applications in a wide range of electronic circuits where high-power amplification or
switching is required:
●Power Amplification: Power transistors are used in audio amplifiers, RF (Radio Frequency) amplifiers, and
other high-power amplification circuits to boost weak signals to higher power levels.
●Switching Circuits: They are employed in switching circuits to control the on/off state of devices like
motors, relays, and LEDs in applications ranging from industrial automation to consumer electronics.
●Voltage Regulation: Power transistors are used in voltage regulation circuits, such as voltage regulators and
voltage stabilizers, to maintain a stable output voltage despite fluctuations in the input voltage.
●Power Inverters: In power inverters, power transistors are used to convert DC (Direct Current) power from
batteries or solar panels into AC (Alternating Current) power for household appliances and industrial
equipment.
Applications
Power Electronic Devices

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Power Diodes
Power diodes are semiconductor devices that
allow current to flow in one direction only,
commonly used in electronic circuits for
rectification and switching applications.
Power Electronic Devices
Power Diodes

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Power diodes are typically made of a semiconductor material like silicon. They consist of two layers: the P-type
(positive) layer and the N-type (negative) layer. The boundary between these layers is called the P-N junction.
Structure
Power Electronic Devices

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When a positive voltage is applied to the anode (P-type material) and a negative voltage to the cathode (N-type
material), it creates a forward bias. In this state, the diode conducts electricity, allowing current to flow from the
anode to the cathode. When the voltage is applied in the reverse direction (reverse bias), the diode blocks the
current flow, acting as an open circuit.
Working Principle
Power Electronic Devices

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Types of Power Diodes
Power Electronic Devices
Rectifier Diodes
These diodes are used for
rectifying alternating
current (AC) into direct
current (DC). They allow
current to flow in only one
direction, converting the
negative half-cycles of AC
into positive DC.
Zener Diodes
While often used for
voltage regulation, Zener
diodes can also be
considered power diodes.
They maintain a constant
voltage across their
terminals when properly
biased, which is useful in
various voltage regulation
applications.
Schottky Diodes
Schottky diodes have a
lower forward voltage drop
compared to regular
diodes, making them
suitable for high-frequency
applications where fast
switching is necessary.

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Types of Power Diodes
Power Electronic Devices
Fast Recovery Diodes
These diodes have a fast
recovery time, meaning they can
switch on and off rapidly. This
characteristic is essential in
applications where rapid
switching is required to minimize
heat dissipation and increase
efficiency.

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●Rectification: Power diodes are fundamental in converting AC to DC in power supplies, allowing electronic
devices to operate on DC power.
●Voltage Regulation: Zener diodes are used for voltage regulation in various electronic circuits, maintaining
a constant voltage across their terminals.
●Switching: Power diodes are used in switching applications, controlling the flow of current in electronic
circuits.
●Protection: Diodes are used in circuits to protect sensitive components from voltage spikes, a common
application being flyback diodes in inductive loads like motors and solenoids.
●Welding: Power diodes are used in welding machines, converting high voltage, low current AC power into
low voltage, high current DC power used for welding.
Applications
Power Electronic Devices

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●Forward Voltage Drop (V_F): The voltage across the diode when it is conducting current.
Different types of power diodes have varying forward voltage drops.
●Reverse Recovery Time (t_RR): The time it takes for the diode to transition from the
conducting state to the non-conducting state when the voltage polarity across the diode is reversed.
Characteristics
Power Electronic Devices

65. Voltage and Current in Electrical Machines

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Voltage and Current in Electrical Machines
Voltage Blocking
●Voltage blocking, also known as voltage blocking diode or reverse voltage protection diode, is a type of
diode used in electronic circuits to prevent reverse voltage from damaging sensitive components.
●Diodes are semiconductor devices that allow current to flow in one direction only and block current in
the opposite direction.
●In the context of voltage blocking, a diode is placed in series with a circuit to ensure that the current can
only flow in one direction, protecting the circuit from potential damage caused by reverse polarity.

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Voltage Blocking
●This property is vital in rectifiers, where alternating current (AC) is converted into direct current (DC).
●Diodes, for example, need to block the negative voltage half-cycle of AC, allowing only the positive
half-cycle to pass through.
●Ensuring diodes can handle this reverse voltage is essential for their proper functioning in rectification
circuits.
Voltage and Current in Electrical Machines

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Voltage Blocking
●Voltage blocking diodes are commonly used in various applications such as power supplies, solar
panels, and battery-powered systems.
●They are essential for preventing accidental reverse polarity connections, which can lead to short
circuits and damage electronic components.
Voltage and Current in Electrical Machines

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Current Conduction Direction
The direction of current flow is
defined as the direction in which
positive charges move. Historically,
early scientists established the
convention that electric current flows
from the positive terminal of a
battery or power source to the
negative terminal. This convention is
called conventional current flow.

In reality, electrons, which are
negatively charged particles, are the
carriers of electric current in most
conductors. Electrons move from the
negative terminal of a power source
to the positive terminal. This
movement of electrons is opposite to
the direction of conventional current
flow.
Voltage and Current in Electrical Machines

70. DC Machine Speed Control

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●DC machine speed control involves varying the voltage applied to the armature (the rotating part of the
motor) to control the speed of the motor.
●By changing the voltage, the electromagnetic torque in the motor is altered, which directly impacts the
speed.
●Lowering the voltage reduces the motor speed, and increasing the voltage speeds it up.
●This method is widely used in applications where precise speed control is necessary, such as in conveyor
systems, electric vehicles, and robotics.
DC Machine Speed Control

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Armature Voltage Control
●Armature voltage control is a method of controlling the speed of a DC machine by varying the voltage
applied to the armature (the rotating part of the machine).
●By changing the armature voltage, the electromotive force (EMF) generated in the armature winding is
altered, which affects the speed of the motor.
DC Machine Speed Control

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How Does Armature Voltage Control Work?
Voltage Variation
By increasing or decreasing
the voltage applied to the
armature, the speed of the
motor can be controlled.
When the voltage is
increased, the motor runs
faster, and when the
voltage is decreased, the
motor slows down.Ṅ
Effect on Torque
The torque produced by the
motor is directly
proportional to the
armature current. When
voltage is increased, the
armature current increases,
producing more torque and
allowing the motor to
overcome higher loads.
DC Machine Speed Control

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Effect on Back
EMF
Speed
Regulation
Field Windings
Flux Control
Flux control involves varying the magnetic field (flux) within the motor. The magnetic field directly influences the
motor's speed.
DC Machine Speed Control

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How Does Flux Work?
Field Windings
DC machines have field
windings that create the
magnetic field. By changing
the current flowing through
these windings, the
strength of the magnetic
field (flux) can be varied.
Effect on Back EMF
The strength of the
magnetic field affects the
back electromotive force
(EMF) generated in the
armature. This back EMF
opposes the applied
voltage and influences the
armature current, thus
affecting the motor's speed.


Speed Regulation
Increasing the field current
strengthens the magnetic
field. This, in turn, reduces
the speed of the motor.
Decreasing the field current
weakens the magnetic field,
increasing the speed.
DC Machine Speed Control

76. © Copyright Intellipaat. All rights reserved.
Any Questions?

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