A Strategy for the Revival of Electric Machines and Drives Courses

Ned Mohan, Mahmoud Riaz, Paul Imbertson, Ted BrekkenDept. of ECE, University of Minnesota

Minneapolis, MN 55455 USAEmail: mohan@ece.umn.edu

- Declining Student Enrollments

- New Opportunities

- Reversing the Trend Using A New Approach [1, 2, 3]

22-Page Article Audio

1

Print Slides

Please click on the Audio button below. Make sure the speakers are turned on.

References

1. NSF-Sponsored Faculty Workshops on Teaching of Electric Drives and PowerElectronics, held at the University of Minnesota, 1994, 1997 and 1998.

2. N. Mohan, Electric Drives: An Integrative Approach, a textbook published by MNPERE, Minneapolis, 2001. This book is reviewed by Professor Marian P. Kazmierkowski, Warsaw University of Technology, Poland in the IEEE Industrial Electronics Newsletter, Vol. 47, No. 3, September 2000. http://sant.bradley.edu/ienews/00_3/edrives.html

3. NSF/NASA-Sponsored Project, “DSP-based, Software-ReconfigurableLaboratory to Nationally Revitalize Electric Drives and Power Electronics Curricula, University of Minnesota, June 1, 2000 – May 31, 2003.

1a

Opportunities

• Energy Conservation [4]

• Transportation

• Harnessing Renewable Wind Energy

• Factory Automation, Robotics

Audio

2

References

4. Turning Point Newsletter, Department of Energy, November 1998. http://www.oit.doe.gov/bestpractices/explore_library/pdfs/tpnov2.pdf

2a

Reversing the Trend of Declining Student Enrollments

PowerProcessing

UnitfixedformElectric Source

(utility)

Controller

Electric Drive

adjustableform

Sensors

input command(speed / position)

Motor

speed /position

Load

- Teaching Electric Drives in the First Course

- DSP-based Lab [3]

Audio

3

References

3. NSF/NASA-Sponsored Project, “DSP-based, Software-ReconfigurableLaboratory to Nationally Revitalize Electric Drives and Power ElectronicsCurricula, University of Minnesota, June 1, 2000 – May 31, 2003.

3a

Meeting the Challenge Using A New Approach

• Deleting Irrelevant Topics

• Discussion of the Power Processing Units

• Sticking to Fundamentals:

• Use of Space Vectors for Analyzing AC Machines

• A Quick Overview of Feedback Controller Design and Utility Interaction

- Discussed at NSF-Sponsored Faculty Workshops [1]

and eme B u f B i= =l l

Audio

4

References

1. NSF-Sponsored Faculty Workshops on Teaching of Electric Drives and PowerElectronics, held at the University of Minnesota, 1994, 1997 and 1998.

4a

A

B

A

B

CM

Vd

+

−

Vd

+

−

iaia

Discussion of Power Processing Units

Rectifier switch - modeconverter

M

controller

utility

−

+dV

PWM-IC

pole-A

( )triv t

, ( )c Av t

A

N

+

−

( )ANv t

( )Aq t

( )Ai t

currentport

voltageport

dV

+

−

+

−

dV

+

−

( )Ad t

tri

1

2V)

( )dAi t

( )ANv t

1

+

/1 2

, ( )c Av t

( )Ai t

Σ

+

M

Audio

5

dV

+

−Ci

Bi

Ai

IC

PWM

A

B

C

n

, ( )c Av t

, ( )c Bv t

, ( )c Cv t

( )Aq t

( )Bq t

( )Cq t

triv

1f

cV

Three Phase Inverter

/1 2

( )Cd t

tri

1

2V

( )Ai t

( )Bi t

( )Ci t

AB

Cn

( )Av t

Σ

( )Bv t ( )Cv t

( )dAi t ( )dBi t ( )dCi t

( )Bd t( )Ad t1

, ( )c Cv t

, ( )c Bv t

, ( )c Av t

dV

( )Ce t

( )Be t

( )Ae t

−

+

−

+

−

+

−

+

tri

1

2V

tri

1

2V+

+

Σ+

+

Σ+

+

1 1

N

,c Av ,c Bv

,c Cv

( )Av t

( )Bv t

( )Cv t

Audio

6

At time ‘t’( )sF t

u ur( )sF tθ

( )aF tu ur

( )bF tu ur

( )cF tu ur

axisc −

axisb −

axisa −

ci = −

bi = −

ai = +

( )aF tu ur

( )bF tu ur

( )cF tu ur

axisc −

axisb −

axisa −

AC Machines: Space Vectors to Represent Sinusoidal Field Distributions

ˆ( ) ( ) ( ) ( ) ( ) ( )s a b c s FsF t F t F t F t F t tθ= + + = ∠u ur u ur u ur u ur

• sinusoidally-distributed windings

Audio

7

ref

ˆma mI I α= ∠ −

α axisa −

ˆms msi I α= ∠ −

u u ur

@ t 0=

α

sI

at time t

magnetic axis of hypothetical winding

ˆwith current sI

axisa −

ˆ( ) ( ) ( ) ( ) ( ) ( )0 0 0s a b c s is

i t i t 0 i t 120 i t 240 I t tθ= ∠ + ∠ + ∠ = ∠ur

ˆ( ) ( ) ( ) ( ) ( ) ( )0 0 0s a b c s vs

v t v t 0 v t 120 v t 240 V t tθ= ∠ + ∠ + ∠ = ∠u ur

Space Vector Representation of Currents and Voltages

Steady State: Relating Phasors to Space Vectors

α

tω0 tω

ˆmI

t 0ω =

( )mbi t ( )mci t( )mai t

Audio

8

Using the Fundamentals

i

l

emf

B

{ {{[ ] [ ][ ] [ ]

emm ANm Tesla

f B i= l1 2 3

{ {{[ ] [ ][ / ][ ]V m m sTesla

e B u= l1 2 3

qf −

qf +

u

(into paper)B

−

+

in DC and AC MachinesE Tk k=

B

Audio

9

Introducing Transformers

• Needed in Power Systems & Power Electronics Courses

• Critical for Understanding of Induction Machines Operation and Control

m 2i i′+

mφ

1N 2N1v

−

+

2i

Load

§ Transformer Analogy

q Flux is unaffected by the loadmφ

Audio

10

Brush-less DC Motor Drives: Principle of Operation

PowerProcessing

UnitUtility

Controlinput

Sinusoidal

PMAC

motor

PositionsensorLoad

Controller

a

b

c

i

i

i

( )m tθ

rBu ur

mθ

axisa −

siur

N

S

sI

axisc −

axisa −

axisb −

N

S

bi

ai

ci

mθ

rBu ur

o90δ =

'a

a

siur

Audio

11

Torque Calculations

rBu ur

ξ

siur

NS

sI

dξ

.. .

ˆ ˆ( ) cos cossem r s

cond lengthfluxdensity atdiff no of cond at

NdT r B I d

2ξ

ξ

ξ ξ ξ ξ= ⋅ ⋅ ⋅ ⋅l14 2 4314 2 43

1 44 2 4 43

/

/

ˆ ˆ( )2

sem em r s

2

NT 2 dT r B I

2

ξ π

ξ π

ξ π=

= −

= × =

∫ l

ˆ ˆ, where the machine torque constant, T

sem s T r

NT k I k r B

2π⇒ = = l

Using emf Bli=

sR

aV

mL

sL6 4 4 4 4 7 4 4 4 4 8

lsL

, r

0E mma BE k 0ω= ∠u ur

−

+ , sma iE ur

aI

−

++ −

, sma iE ur

+

−

E Tk k=

Audio

12

Induction Motor: Induced Currents in Rotor

mω−− − −

−

+

+

+

+

msBu u u ur

synω

synω

axisa −

at t 0=

svuur

θ

( )bari θ

barR

back end-ring front

end-ring

θ + −

+ −+ −

+ −

+−

+−+−+−

+−

+ −

bare

msBu u u ur

synω

'ma rai i+

net flux = 0

, 'rm iφ

, rm iφ

svuur

axisa −

mω

at t 0=

axisa −sv

uur

msBu u u ur

msiu uur

rF ′u ur

rFu ur

'riu ur

at t 0=

siur

Click Here For Inclusion of Rotor Leakage Inductance

Audio

13

Including Rotor Leakage Inductance

maI'raI

aV

aI

+

−

(at )ωaV

+

−

lsj Lω

maImaE

'raIaIsR

'lrj Lω

'syn

rslip

Rω

ωmj Lω

rθ

rθ

m siu u uur

synω

synωaxisa −

msBu u uur

rFu ur

'rFu u ur ( )sv t

uur

at t 0=

'riu ur

ri′urrF ′

u ur

rFu ur

rθ

rθ

axisa −

msBu u uur

rBu ur

lrBu u ur

at t 0=

o90

o90

svuur

Audio

13a

Electromagnetic Torque

'rFu u ur

rFu ur

axisa −

'riu ur

at t 0=

l

svuur

msBu u u ur

(a)

ω m

Tem

f1

f2

f3

ω syn rated,

ω slip,1

frated

ω syn ,1

0

,syn ratedω

mω

,m ratedω

,em ratedT emT0

,slip ratedω

Click Here For Motoring vs. Reg. Braking

Audio

14

2ˆ ˆ ˆ 2

t

sem ms r e ms slip

k

NT r B I k B

ωπ ω′= =l14 2 43

Regen. (Braking) ModeMotoring Mode

m synω ω< m synω ω>

Motoring vs. Regenerative Braking

msBu u u ur

synω

'ma rai i+

net flux = 0

, 'rm iφ

, rm iφ

svuur

axisa −

mω

at t 0=

rFu ur

'rFu u ur

mω

synω

axisa −

msBu u u ur

Audio

14a

*position+

−

*speed *torque

torque(current)

SpeedPositioncontroller

torque

Torque ElectricalSystem

Mech position

speed

speed

position

1

scontroller+

−

+

−

controller System

Feedback Controller Design

Various Utility Interface

Optional Topics

Audio

15

Topics No. of LecturesIntroduction to Electric Drive Systems 1

Understanding Mechanical System Requirements 2

Review of Electric Circuits 1

Basic Understanding of Switch-Mode Power Electronics 4

Magnetic Circuits 4

Basic Principles of Electro-Mechanical Energy Conversion 3

DC-Motor and ECM Drives 5

Introduction to AC Machines and Space Vectors 5

Sinusoidal PMAC Drives and Synchronous Machines 4

Induction Machines: Steady State Analysis 5

Adjustable-Speed Induction-Motor Drives 3

Optional Topics

Feedback Controller Design

Power Quality Issues

Reluctance Drives

Approx. 40 Lecture Sequence

Audio

16

A DSP-Based Lab for the First Course

DC Power SupplyDSP Board

M

Active Load

Switching Signals Switching Signals

Data

Optical Encoder

Fig. 23 DSP-based Lab.

Audio

17

References

1. NSF-Sponsored Faculty Workshops on Teaching of Electric Drives and PowerElectronics, held at the University of Minnesota, 1994, 1997 and 1998.

2. N. Mohan, Electric Drives: An Integrative Approach, a textbook published byMNPERE, Minneapolis, 2001. This book is reviewed by Professor Marian P. Kazmierkowski, Warsaw University of Technology, Poland in the IEEE Industrial Electronics Newsletter, Vol. 47, No. 3, September 2000. http://sant.bradley.edu/ienews/00_3/edrives.html

3. NSF/NASA-Sponsored Project, “DSP-based, Software-ReconfigurableLaboratory to Nationally Revitalize Electric Drives and Power Electronics Curricula, University of Minnesota, June 1, 2000 – May 31, 2003.

4. Turning Point Newsletter, Department of Energy, November 1998. http://www.oit.doe.gov/bestpractices/explore_library/pdfs/tpnov2.pdf

continued…

18

References

5. N. Mohan and J. Ramsey, Comparative Study of Adjustable Speed Drives for Heat Pumps, EPRI Final Report EM-4704, Project 2033-4, August 1986.

6. N. Mohan, Advanced Electric Drives: Analysis, Control and Modeling using SIMULINK™, to be printed in August 2001 by MNPERE, Minneapolis, MN.

7. Instructor’s CD to accompany [2].

8. DSPACE GmbH, Technologiepark 25, 33100 Paderborn, Germany. http://www.dspaceinc.com

19