Motor Design and Power Electronics (course).PDF

G2 Consulting - Motor Design and Power Electronics (course)

G2 Consulting

16985 S. W. Kemmer Road

Course Contents

CHAPTER 1: MAGNETIC PRINCIPLES

1.1 Introduction

1.2 Magnetic circuits and the design equations

1.3 Sample calculation of magnetic flux design in a gap

1.4 The B-H curves of PM materials

1.5 Excursions of the operating points

1.6 Energy product and maximum energy product

1.7 Intrinsic and normal B-H curves

1.8 Magnetic forces on permeable materials

CHAPTER 2: MAGNETIC MATERIALS

2.1 Magnetically hard (PM) materials

2.2 Magnetically soft materials

CHAPTER 3: FLUX, RELUCTANCE AND PERMEANCE

3.1 Intuitive concept of flux

3.2 Reluctance and permeance

3.3 General formulation of reluctance

3.4 Roter's method

3.5 Numerical calculations of magnetic fields

3.5.1 Finite difference method

3.5.2 Finite element method

CHAPTER 4: ELECTROMAGNETICS

4.1 Force and emf generation

4.2 Transformer operation

4.3 Instruments of magnetics

CHAPTER 5: MAGNETIZING OF PERMANENT MAGNETS

5.1 Magnetizing requirements

5.2 Current vs. time in an ideal magnetizer

5.3 Real magnetizers

5.4 Optimization

5.5 Other considerations

5.6 Forces on conductors and coils

5.7 Winding patterns

CHAPTER 6: MOTOR DYNAMICS

6.1 Force production

6.1.1 Forces between a conductor and steel

6.2 Energy considerations

6.2.1 The force equation

6.3 Torque balance equation

6.3.1 Dynamic determination of torque

6.3.2 Torque development by 2 fields

CHAPTER 7: MOTOR DESIGN

7.1 Introduction

7.2 Overall dimensions

7.3 The magnetic circuit

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G2 Consulting - Motor Design and Power Electronics (course)

7.4 Magnet performance

7.5 Design features

7.6 Motor winding

7.7 Winding connections

7.8 Motor characteristics

7.9 Loss calculation

7.10 Armature reaction and demagnetization

7.11 Acceleration

7.12 Designing with computers

CHAPTER 8: MANUFACTURING CONSIDERATIONS

8.1 Introduction

8.2 Laminations

8.2.1 Die punching

8.2.2 Chemical etching

8.2.3 Laser cutting

8.3 Stator stack

8.4 Winding

8.5 Magnet magnetization

8.6 Bearing assembly

CHAPTER 9: ELECTRONIC CONTROLLERS

9.1 Types of drives

9.2 Speed control

9.3 Sensorless control

CHAPTER 10: STEPPER MOTORS

10.2 Torque characteristics

10.3 Electromagnetic principles

10.4 Stepper design tips

CHAPTER 11: ACTUATORS

11.1.2 Basic principles

11.1.3 Shorted turn

11.1.4 Equivalent circuit

11.1.5 Static magnetic circuit

11.1.6 Coil construction

11.1.7 Improving linearity

11.1.8 Actuator dynamics

11.2 Solenoids

11.2.1 Introduction

11.2.2 First order force calculation

11.2.3 Idealized model

11.2.4 Bobbin and winding

11.2.5 Packing factor

11.2.6 Gap location

11.2.7 Plunger face shape

11.2.8 Remanence and sticking

11.2.9 The plunger-wall flux crossing region

11.2.10 Solenoid drive circuit consideration

11.2.11 Solenoids operating against springs

11.2.12 Constant force variable position solenoid

11.2.13 Solenoid actuation speed

11.2.14 Some other solenoid types

11.2.14.1 AC solenoids

11.2.14.2 Rotary solenoids

11.2.15 Testing of solenoids

11.3 Linear multiphase motors

11.4 Other actuators

BIBLIOGRAPHY

LIST OF SYMBOLS

UNIT CONVERSION FACTORS

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CHAPTER 1

MAGNETIC PRINCIPLES

1.1 Introduction:

Thousands of years ago it was noticed that certain rocks were attracted

to iron by some mysterious means. There were deposits of such rock in the

area known as Magnesia, in what is now Turkey, and from the name they

came to be called magnets. They were also called lodestones, which means

"journey stone". If a needle was rubbed on a lodestone and then floated

on a piece of wood in water or hung on a string, it would point in a

North-South direction. The end which pointed North was called a

north-seeking pole, or just a north pole. Since opposite poles attract,

it can be seen that the earth's geographic north pole is a magnetic south

pole!

If one is unsure where the north pole of a magnet is, the old experiment

can still be used, by hanging the magnet on a string and watching how it

turns. Avoid nearby automobiles and steel belt buckles. The suspension

must have very little torsional stiffness, because the magnet can't exert

much torque (a piece of tape is too stiff).

Magnetism was investigated by scientific methods long before electricity

was discovered, and "unit poles" were used to describe them. Later,

electrical units were introduced, as the interrelationships between them

became understood. The metric system came into being, with still

different units, and went through several revisions before arriving at

its present form (called SI). Today there is a wild jumble of units in

common use, which makes it difficult for newcomers to the field. In this

seminar, the units presented will be those normally used in engineering

in the US today. Moreover, industrial measuring devices indicate in those

units and most printed engineering data is given in them. They are

somewhat mixed between English, "old" metric and new metric. This is

unscientific, but practical. Because of the very great extent of material

to be covered in a very short time, there will be little opportunity to

show the many elegant mathematical proofs with which the field abounds.

They are important, but had to be set aside in order to show as much of

the material which is directly useful for design as possible. The

interested investigator should then be able to find and study these

mathematical developments in the references.

In the early studies of magnetism, it was felt that something was flowing

in and out of the magnet poles and it came to be called

flux. The same thing was thought about electricity and in that case it

was true. Magnetic flux, however, does not exist, in the physical sense

of the motion of matter. It certainly isn't concentrated into "lines", of

course, even though we draw lines representing flux flow. The fact that

there is a unit of flux called a "line" doesn't help get the concept

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across. Iron filings on a surface above a magnet tend to gather into

paths somewhat randomly, aligned in the direction of flux flow.

Nonetheless, flux is not divided into lines.

Even though flux does not exist, it is useful to pretend that it does.

There are a number of different "models" or means of description by which

magnetics may be considered. They are all somewhat artificial, but are

helpful in understanding and predicting magnetic behavior. The older

"unit pole" model is one example. It was proposed hundreds of years ago

and physicists have been looking for a single magnetic pole (as

distinguished from a pole pair) ever since, without much success. This

seminar will generally follow the "flux" model. Later on the "potential

field" model will be discussed briefly. None of these can be said to be

more "correct" than the others; they are just different ways to consider

the same thing, and in any given situation, one approach may be easier to

understand than another. Each leads to the same conclusion, with

different degrees of difficulty.

1.2 Magnetic circuits and the design equations:

A simple electric circuit is shown in Figure 1.1 with a battery,

conducting wire and two resistors and . The current in the circuit is

determined by the well-known Ohm's law:

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In a magnetic circuit, flux is defined as the integral of the magnetic

induction or flux-density B times a differential of area normal (at right

angles) to the direction of B. The unit of B in US engineering practice

is the Gauss (G). The equivalent SI unit, the Tesla, is equal to 10,000

Gauss and is also sometimes used. The induction B is the quantity

measured by Gauss meters, and is the magnetic property useful in

calculating forces on electric wires, steel pole pieces etc. It is a

vector, with a direction as well as strength. If the Gauss meter probe is

normal to the flux direction, it will indicate the strength of B; at any

other angle it will show a lower value. If turned over, it will show the

same value (hopefully!) with sign reversed.

In the electric circuit of Figure 1.1, the same current flowed

through both and . In the magnetic circuit of Figure 1.2, idealized

with no leakage flux (that is, all the flux goes through the gaps), the

flux crossing gap (1) is , the B's being magnetic induction (assumed

constant at every point in the gap) and the A's being the cross-sectional

area. The same flux must cross the second gap.

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