**EDB3053**

ELECTRICAL MACHINES

ELECTRICAL MACHINES

**1. Introduction to**

Machinery Principle

Machinery Principle

**2. Transformer**

**3. AC Machines**

**4. DC Machines**

**Synchronous Generator**

**Induction Motor**

**DC Motor**

**DC Generator**

Learning Outcome

Understand the

fundamental laws

in the

dynamic magnetic

systems and their relation to the electrical machines.

The Magnetic Field Principle

What is an Electrical Machine?

Equipment that is able to

convert

either

mechanical

energy to

electric

energy, or electric energy to mechanical energy.

The process is also known as

electromechanical energy conversion.

Power Concept

Magnetic field produces

when

current flow

in a wire

A

time changing magnetic field

induces voltage

in a coil of wire if it is passes through the coil.

Basis of transformer

“A

current-carrying wire

in the presence of

magnetic field

has

force induced

on it” (Basis of

motor

)

A

moving wire

in the presence of a

magnetic field

has a

voltage induced

in it” (Basis of

generator

)

Faraday’s Law

Ampere’s Law

Electromagnetic Force

(Lorentz force)

Second Newton’s Law

In Electrical Machines

The Magnetic Field

Production of Magnetic Field

Magnetic Circuits

Example

Magnetic Behavior of Ferromagnetic Material

Energy Loss in a Ferromagnetic Material

Hysteresis Loss

Eddy Current Loss

Hysteresis Loss

Eddy Current Loss

INTRODUCTION TO MACHINERY PRINCIPLE

By:

Mohd Fakhizan Romlie, PhD

Email: fakhizan.romlie@petronas.com.my

Transformers

Voltage Regulation

2.Why Transformers are Important?

Make electricity generation possible at the most economic generator voltage level

Make electric power transmission take place at the most economic transmission voltage

Supply electric power to users at a safe and suitable voltage

Autotransformer

By:

Mohd Fakhizan Romlie, PhD

email: fakhizan.romlie@petronas.com.my

Learning Outcomes

1.What is a Power Transformer?

A device that changes AC electric power voltage level to AC electric power another voltage level at the same frequency through magnetic field action

Consist of two or more coils of wire wrapped around a common ferromagnetic core

Construction & How it works

Ideal Transformer

vs

Real Transformer

Ideal Transformer

Real Transformer

Per Unit System

Three Phase Transformer

How does a Transformer Work ?

Construction

The permeability of the core, approaches infinity

No core losses

No resistance in the windings

No leakage flux

Therefore:

Schematic Diagram

Example

Power

Impedance Transformation

Understand the purpose of a transformer in a power system

Know the voltage, current and impedance relationships across the windings of an ideal transformer

Understand how real transformers approximate the operation of an ideal transformer

Be able to explain how copper losses, leakage flux, hysteresis and eddy current are modeled in a transformer equivalent circuit

Use the transformer equivalent circuit to find the voltage and current transformations across a transformer

Be able to calculate the losses and efficiency

Be able to derive the equivalent circuit of a transformer from measurement

Understand per unit system

Be able to calculate voltage regulation

Understand auto transformer

Understand three phase transformers

Solution

LOSSES

ACCOUNTED

???

1. Copper Losses

2. Eddy Current Losses

4. Leakage Flux

3. Hysteresis Losses

EQUIVALENT CIRCUIT

OPEN CIRCUIT TEST

Referred to Primary Side

Referred to Secondary Side

Approximation - current excitation branch 2-3% only

Resistive heating losses in the primary and secondary winding of transformer. Proportional to square of current.

Resistive heating losses in the core of transformer. Proportional to square of voltage applied to transformer.

Associated with magnetic domains in the core. It is a function of voltage applied to the transformer.

Flux escape from the core and pass through only one side of the transformer. Its produce leakage inductance in the primary and secondary winding.

How?

1. Select 2 base quantities

- usually selected - voltage and power

2. Use electrical law

Example

Eliminates the need for voltage-level conversions and impedance transformation at every transformer.

Machine and transformer impedances fall within a fairly narrow range according to voltage and power ratings of the device.

Efficiency

EXAMPLE

Example

Voltage and Current Relationship

Apparent Power Rating

Advantage

The Internal Impedance

Example

AC Machinery Fundamentals

Rotating Magnetic Field

Student should be able to explain using their own words - with proper diagrams

Definition

LO

Evaluate the fundamental operation of AC Machines

Voltage Regulation and Speed Regulation

AC Machines Power Flow and Losses

A Simple Loop in a Uniform Magnetic Field

By:

Mohd Fakhizan Romlie, PhD

email: fakhizan.romlie@petronas.com.my

Voltage Induced?

Forced Induced?

Detail explanation with equations related in section 3.1 of Chapman

Student should be able to explain the concept using their own words - with proper diagrams

Motor Power flow

Generator Power Flow

Generator - Voltage Regulation

Motor - Speed Regulation

The ability of a generator to keep a constant voltage at its terminals as load varies.

Ability of a motor to keep a constant shaft speed as load varies

Synchronous Generators

Speed

Construction and Operation Principle

LO

Analyze the performance characteristics of synchronous machines

How to Obtain Model Parameters?

Equivalent Circuit

Internal Generated Voltage

By:

Mohd Fakhizan Romlie, PhD

email: fakhizan.romlie@petronas.com.my

Source: http://articles.maritimepropulsion.com/author/Henderson.aspx?page=6

Phasor Diagram

Example

POWER AND TORQUE

Synchronous Generator Operating Alone

Induction Motor

Induction motor Construction

How it work?

LO

Torque

Torque Equation

Power Flow

Basic Concept

Analyze performance and characteristic of induction machine

Wound rotor

Squirrel Cage

Induction

Rotor Slip

Electrical Frequency

Example

Equivalent Circuit

Remember this

Transformer Model

Rotor Circuit Model

Final Equivalent Circuit

3hz

1710rpm

1800rpm

Maximum (Pullout Torque)

Torque-Speed Characteristic

Quiz

How we are going to do it?

1. 3 mins - individually - draw equivalent circuits and power flow diagram and think of how to do this example.

2. 5 mins - discuss with person next to your (in pair) - how to calculate all question. Don't calculate. Just write down how and write down formula to be used to calculate all question...

3. Discussion - I will randomly call anybody to come fw

4. Submit the quiz - at the end..

DC GENERATOR

FUNDAMENTALS AND CONSTRUCTION

Main Parts:

- stator

- rotor

-winding

-commutator

-brush

Internal Generated Voltage

Induced Torque

DC MOTOR

LO

Students should be able to :

- Describe the

equivalent circuit

for different types of DC motors

- Describe the

terminal characteristics

(torque vs. speed) for a DC motor

- Determine

speed and torque generated

by a DC motor given its terminal characteristics and magnetization curve

Separately Excited

Shunt Excited

Series Excited

Compounded

Permanent Magnet

Terminal Characteristic

Power Flow

Speed Control