Lecture Electromechanical energy conversion: Magnetic circuits and magnetic materials - Nguyễn Công Phương

Lecture Electromechanical energy conversion - Magnetic circuits and magnetic materials presents the following content: Introduction to magnetic circuits; flux linkage, inductance, and energy; properties of magnetic materials; AC excitation; permanent magnets; application of permanent magnet materials.

Trang 1

Nguyễn Công Phương

ELECTROMECHANICAL ENERGY

CONVERSION

Magnetic Circuits and Magnetic Materials

Trang 2

I Magnetic Circuits and Magnetic Materials

II Electromechanical Energy Conversion

Principles

III Introduction to Rotating Machines

IV Synchronous Machines

V Polyphase Induction Machines

VI DC Machines

VII.Variable – Reluctance Machines and Stepping

Motors

VIII.Single and Two – Phase Motors

IX Speed and Torque Control

Trang 3

1 Introduction to Magnetic Circuits

2 Flux Linkage, Inductance, and Energy

3 Properties of Magnetic Materials

4 AC Excitation

5 Permanent Magnets

6 Application of Permanent Magnet Materials

sites.google.com/site/ncpdhbkhn 3

Trang 4

Introduction to Magnetic Circuits

µ

=

Trang 5

0 0.5

Trang 6

Trang 8

(5)

µ >> µ 0 : the magnetic flux is confined

almost entirely to the core

F = Ni : magnetomotive force (mmf)

+ –

Magnetic core permeability µ

Mean core length, lc

Trang 9

(6)

+ –

Trang 10

(7)

+ –

Trang 12

c g

R R F

Trang 13

The core is made of nickel – iron alloy

Find the current i?

+ –

Trang 14

(11)

Ex 2

Given Φ = 0.141 mWb, S c = S g = 4cm 2 ,

l c = 44cm, g = 0.2cm, N = 400 turns

The core is made of nickel – iron alloy

Find the current i?

+ –

F i

N

→ = = =

Trang 15

N = 500 turns Rotor and stator are made

of iron (infinite permeability) Find the

flux of the air gap?

Trang 16

Trang 17

2 Flux Linkage, Inductance, and Energy

4 AC Excitation

5 Permanent Magnets

Trang 18

Flux Linkage, Inductance, and

R

→ =

Trang 19

Find the inductance of the winding and

the flux density of gap 2?

Trang 20

Find the inductance of the winding and

the flux density of gap 2?

1 1

1

Ni B

g

µ

Trang 21

g

g R

Trang 22

Energy (5)

x 1040

Trang 24

Energy (7)

d e

Trang 25

λ = → =

Trang 26

Energy (9)

Ex 3

3 A turns 3.07 10

A turns 2.49 10

dt

1000 (16 10 ) 314 cos(314 )− t

= × × × = 502 cos(314 ) t

Trang 27

3 Properties of Magnetic Materials

4 AC Excitation

5 Permanent Magnets

Trang 28

Properties of Magnetic Materials

(1)

Magnetic materials can be used:

• To constrain and direct magnetic fields in well – defined paths

• In transformer:

– To maximize the coupling between the windings, and

– To lower the excitation current required for

transformer operation

• In electric machinery:

– To shape the fields to obtain desired torque –

production and electrical terminal characteristics

• The most common: ferromagnetic materials

Trang 29

(2)

Trang 30

(2)

Trang 32

Trang 33

4 AC Excitation

5 Permanent Magnets

Trang 34

c c rms rms

l H I

N

ϕ =

Trang 35

AC Excitation (2)

, max ,

Trang 36

AC Excitation (3)

• The exciting current i supplies the mmf needed to

produce:

– the core flux, and

– the power input associated with the energy in the

magnetic

• This energy:

– Part is dissipated as losses & results in heating of the

core (RI 2 )

– The rest appears as reactive power, it is not dissipated

in the core, but cyclically supplied & absorbed by the excitation source

Trang 37

AC Excitation (4)

Trang 38

AC Excitation (5)

Ex.

The winding is excited with a 60-Hz voltage to

produce B = 1.6sinωt T, the steel occupies 0.94 of the

core cross-sectional area, ρc = 7.65 g/cm3 Find:

a) The applied voltage?

b) The peak current?

c) The rms exciting current?

d) The core loss?

1.6 sin(2 60 ) 1.6 sin 377 T

+ –

2(15 10 15 10) 10 70

Trang 39

AC Excitation (6)

Ex.

d) The core loss?

+ –

c

E I P

a rms

rms

P W I

E

=

Trang 40

AC Excitation (7)

Ex.

d) The core loss?

+ –

c total c c

P = PW

= ×

=

Trang 41

4 AC Excitation

5 Permanent Magnets

Trang 42

Permanent Magnets (1)

Trang 44

Point of maximum energy product

m m

Vol B Vol

H B

µ

−

Trang 45

Trang 46

Application of Permanent Magnet

Materials (1)

Trang 47

N

turns

Trang 48

Application of Permanent Magnet

a) Find the magnet length such that the system will

operate on a recoil line which intersects the

maximum B – H product point on the magnetization

curve.

b) Calculate the flux density in the air gap as the

plunger moves back and forth.

Trang 49

a) Find the magnet length such that the system will

operate on a recoil line which intersects the

maximum B – H product point on the magnetization

curve.

b) Calculate the flux density in the air gap as the

plunger moves back and forth.

mS

Định dạng
Số trang	49
Dung lượng	1,79 MB