Outlook - IEADCMachine).pdf · 2019-02-13 · L8: DC machine theory and control L4: 13-FEB-2019 Lund University / LTH / IEA / AR / EIEN25 /2019-02-13 2 Outlook •Operation principle

L8: DC machine theory and control

L4: 13-FEB-2019

Lund University / LTH / IEA / AR / EIEN25 /2019-02-13 2

Outlook

• Operation principle

• DC machine constructions

• Armature winding and commutation

• DC machine parameters and model

• Machine characteristics

• Torque and speed control of DC machine


Rotating coil in magnetic field

• If the coil rotates in a magnetic field, the flux linking the coil will be an alternating quantity

• Connection via sliprings– alternating voltage

• Connection via commutator – “rectified”voltage

B

eθ

B

e

θ


Working principle

221

222

00

BdAede

BlrBBlrBlue

av

• Current carrying conductor in magnetic field

• Magnetic field created by field coil or permanent magnets

• As the armature rotates the 2 coil sides move in the magnetic field

S N B

iBilrdT

BBilrBlirFrT

av

2

21

222

0

B

I

F


DC machine constructions A

• Permanent magnet DC machines– Small machines

– Three coils, 120 shifted

– PM on stator or on rotor

• Commutation– Mechanic via commutator

– Electric via 3-phase bridge

• Torque generation– SN arrangement of PM for field ψ

– Coil energizing I for torque T

– Torque direction and energizingsequence

+A

-B

+B

-C

+C

-A

+A

-B

+B

-C

+C

-A

Brushed DC motor

Brushless DC motor


DC machine constructions B

• Magnetized, loaded & armature field


Commutator

Stator field fluxRotor flux

Rotor

Commutator

Rotor fluxStator field flux

Rotor

Comm

utato

r

Stator field fluxRotor flux

Rotor

Commutator

RotorCommutator

Stator field flux

Brushes


DC machine construction C• Stator with salient poles &

cylindrical rotor

• Armature winding, field and armature reaction

• Commutating (inter) pole –neutralize flux distortion in the neutral plane caused by armature reaction

• Compensating winding –embedded in pole phases, in series with the armature, neutralizing the cross-magnetizing field

If

Ia Armature field

Excitation field


Armature winding

• Layouts– Lap winding– Wave winding

• Current distribution rectangular

• MMF distribution triangular


Field winding and excitation

• Separately excited

• Self excited– Series wound

– Shunt wound

– Compound wound

• Long shunt

• Short shunt

au fu


Series motor• Rotor current = the field

current• Torque is independent of

current direction• Used in many handhold

machines• Used as traction motors

for railways

+ ua -

2amam iLiT


DC machine model

• Armature (rotor)

• Excitation (stator)

• Torque (gap)

• Torque (shaft)

ma

aaaa dt

diLiRu

T=m·ia

fmffmm

fffff

LLLiLdt

diLiRu

Js

TTdt

J

TT

TTdt

dJJ

dt

d

elel

lel

Back EMF


Summary of DC machine

• Rotation Commutator on the rotor shaft

• Voltage Proportional to motorspeed

• Torque Proportional to rotor current

m

0a

x

y


0 1 2 3 4 5 6 7 8 9 100

5

10

15

20

25

volta

ge,

u [V

]

time, t [s]

T

ua

ea

0

0.5

1

1.5

2x 10

4

spee

d, n

[rp

m]

n

0

50

100

150

200

250

curr

ent,

Ia

[A]

I

0 1 2 3 4 5 6 7 8 9 100

0.5

1

1.5

2

2.5

3

torq

ue,

T [

Nm

]

Brushed PM DC machine example

• Parameters– Voltage Ua=24V

– Speed n=18000 rpm

– Flux linkage ψ=E/ω

– R, L, J arbitrary, b=0

1

J.s

1

L.s

e

ia

T

w

t

M

b

M

R

Tm ec

ua

Clock

0 2000 4000 6000 8000 10000 12000 14000 16000 180000

0.5

1

1.5

2

2.5

3

torq

ue,

T [

Nm

]

speed, n [rpm]0 2000 4000 6000 8000 10000 12000 14000 16000 18000

0

500

1000

1500

pow

er,

P [

W]


DCM

• Uf=200V, Rf=200Ω, if=1A,Psim=1.23Vs

• Tload=10Nm

Psif

EXCIT AT ION FIELD DYNAM ICS

ANCHOR DYNAMICS

ROT OR DYNAMICS

Rf

i f = f (Psif )

1

J.s

1

L.s

e

ia

T

ie

w

psim

t

1/s

bR

K

uf

T mec

ua

Clock

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10

50

100

150

200

volta

ge,

u [V

]

time, t [s]

T

ua

ea

0

500

1000

1500

spee

d, n

[rp

m]

n

0

10

20

30

40

50

60

70

curr

ent,

Ia

[A]

I

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10

10

20

30

40

50

60

70

torq

ue,

T [

Nm

]

-200 0 200 400 600 800 1000 1200 14000

20

40

60

80

torq

ue,

T [

Nm

]

speed, n [rpm]-200 0 200 400 600 800 1000 1200 1400

0

1000

2000

3000

4000

pow

er,

P [

W]


DCM Drive without PEC

Psif

EXCIT AT ION FIELD DYNAM ICS

ANCHOR DYNAM ICS

ROTOR DYNAMICS

CURRENT PIE REGULAT ORSPEED PI REGULATOR

vol tage l im it

torque

li mi tati on

Rf

Kpw Ki w

if = f(Psif )

1

Psim

current

reference

current lim itati on

Kaw

Kai

1

J.s

1

L.s

e

ia

T

iar

ua

ie

w

p sim

t Kpi

Ki i

1/s

bR

K

T

z-1

T

z-1

wref

uf

T mec

Clock

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 20

50

100

150

200

volta

ge,

u [V

]

time, t [s]

T

ua

ea

0

500

1000

1500

spee

d, n

[rp

m]

n

0

5

10

15

20

curr

ent,

Ia

[A]

I

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 20

5

10

15

20

25

torq

ue,

T [

Nm

]

• Free acceleration under current limit

• P and PE regulators only!

-200 0 200 400 600 800 10000

5

10

15

20

25

torq

ue,

T [

Nm

]

speed, n [rpm]-200 0 200 400 600 800 1000

0

200

400

600

800

1000

1200

pow

er,

P [

W]


Torque control

• Torque is proportional to current

• Current control– Direct current control

(DCC)

– Sampled current control (SCC) PIE regulator

forwardFeed

Integral

kn

ns

s

oportionals

kn

ns

s

s

keniniT

R

LT

kikiR

T

L

keniniRkikiR

T

L

keT

kikiLkiR

kikiR

keT

kikiL

kikiRku

)()()(*

2

)()(*2

)()()(*)()(*2

)()()(*

)(2

)()(*

)()()(*

2

)()(*)(*

1

0Pr

1

0

i

increase

rest

decrease

[1, -1]

[1,1] or [-1, -1]

[-1,1]

[sa, sb]


Field weakening

nomrrr

nomrnomm

nomrrnomm

m

nommnomra

mra

if

if

e

e

,,

,

,,*

,,max,

nom max

m

fi

*fi

Voltage, Power

Torque, Flux

Speed

Rotor current


Electric drive system with DCM

• 1QC armature winding – uni-directional torque and speed

• 2QC armature winding – acceleration and regenerative breaking

• 4QC armature winding – bi-directional torque and speed


Exercises on DC machine (4)

• PE ExercisesWithSolutions2019b vers 190206

• DC machine construction (4.16a)

• DC machine equations (4.16b-c)

• DC machine parameters and performance (4.17)

• DC machine control and parameters (4.18)

• Electric drive system specification for DC machine

Documents

Outlook - IEADCMachine).pdf · 2019-02-13 · L8: DC machine theory and control L4: 13-FEB-2019 Lund University / LTH / IEA / AR / EIEN25 /2019-02-13 2 Outlook •Operation principle