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1Challenge the future
Overview Electrical Machines and
Drives
• 7-9 1: Introduction, Maxwell’s equations, magnetic circuits
• 11-9 1.2-3: Magnetic circuits, Principles
• 14-9 3-4.2: Principles, DC machines
• 18-9 4.3-4.7: DC machines and drives
• 21-9 5.2-5.6: IM introduction, IM principles
• 25-9 Guest lecture Emile Brink
• 28-9 5.8-5.10: IM equivalent circuits and characteristics
• 2-10 5.13-6.3: IM drives, SM
• 5-10 6.4-6.13: SM, PMACM
• 12-10 6.14-8.3: PMACM, other machines
• 19-10: rest, questions
• 9-11: exam
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2Challenge the future
DC machines
• Introduction, construction (4.2)
• Principle of operation and basic calculations (4.2)
• Armature reaction, interpoles, compensating winding (4.3)
• Characteristics, means to control speed (4.4)
• DC machine drives (4.5)
• Ward-Leonard system
• Power electronics (Rectifier, Chopper)
• Closed loop control
• PMDC machines / PCB machines (4.6, 4.7)
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Ward-Leonard system
• dates from 1890
• is robust; can be overloaded
• is expensive and inefficient
Why does a diesel-electric locomotive have a comparable drive system?
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Drive with power electronics
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From DC source: chopper
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From AC source: (controlled) rectifier
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DC machines
• Introduction, construction (4.2)
• Principle of operation and basic calculations (4.2)
• Armature reaction, interpoles, compensating winding (4.3)
• Characteristics, means to control speed (4.4)
• DC machine drives (4.5)
• Ward-Leonard system
• Power electronics (Rectifier, Chopper)
• Closed loop control
• PMDC machines / PCB machines (4.6, 4.7)
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Closed loop speed control
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Closed-loop speed control with
inner current loop
• Why add an inner current loop?
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DC machines
• Introduction, construction (4.2)
• Principle of operation and basic calculations (4.2)
• Armature reaction, interpoles, compensating winding (4.3)
• Characteristics, means to control speed (4.4)
• DC machine drives (4.5)
• PMDC machines (4.6, 4.7)
• iron armature
• hollow rotor
• disc armature
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PM DC machine
Advantages:
• no field losses
• smaller machine
Disadvantages
• risk of demagnetisation
• no field control
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Iron armature motor
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Hollow rotor motor
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Disc armature motor
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DC machines
• Introduction, construction (4.2)
• Principle of operation and basic calculations (4.2)
• Armature reaction, interpoles, compensating winding (4.3)
• Characteristics, means to control speed (4.4)
• DC machine drives (4.5)
• PMDC machines (4.6, 4.7)
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16Challenge the future
Overview Electrical Machines and
Drives
• 7-9 1: Introduction, Maxwell’s equations, magnetic circuits
• 11-9 1.2-3: Magnetic circuits, Principles
• 14-9 3-4.2: Principles, DC machines
• 18-9 4.3-4.7: DC machines and drives
• 21-9 5.2-5.6: IM introduction, IM principles
• 25-9 Guest lecture Emile Brink
• 28-9 5.8-5.10: IM equivalent circuits and characteristics
• 2-10 5.13-6.3: IM drives, SM
• 5-10 6.4-6.13: SM, PMACM
• 12-10 6.14-8.3: PMACM, other machines
• 19-10: rest, questions
• 9-11: exam
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17Challenge the future
Induction machines
• Introduction (5.1)
• Rotating magnetic field (5.2, also for SM)
• Why does an induction machine rotate?
• Induced voltage (5.3, also for SM)
• Definitions (5.4, 5.5)
• Equivalent circuits and voltage equations (5.7)
• Parameter identification (5.8)
• Performance characteristics (5.9)
• Power flow in three modes of operation (5.10)
• Speed control (5.13)
• Linear induction motors (5.16)
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Introduction induction machines
• Why induction machines?
• cheap
• robust
• How are they used?
• motor
• generator in wind turbines
• How do they look?
• cylindrical rotor and stator bore
• laminated stator and rotor
• squirrel-cage rotor or wound rotor
• sinusoidally distributed stator winding
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Three-phase induction machines
axes of the windingsthree phases
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Cutaway view of an induction
machine
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Three-phase stator winding
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Three-phase stator winding
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Squirrel cage rotor induction
machine
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Wound rotor IM
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25Challenge the future
Induction machines
• Introduction (5.1)
• Rotating magnetic field (5.2, also for SM)
• Why does an induction machine rotate?
• Induced voltage (5.3, also for SM)
• Definitions (5.4, 5.5)
• Equivalent circuits and voltage equations (5.7)
• Parameter identification (5.8)
• Performance characteristics (5.9)
• Power flow in three modes of operation (5.10)
• Speed control (5.13)
• Linear induction motors (5.16)
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Magnetic field of one phase
• one phase gives
pulsating
magnetic field
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Assumptions
• Permeability of iron is infinite
• Stator winding is sinusoidally distributed
• Magnetic field crosses the air gap perpendicular
• Magnetic field in the air gap is not a function of the radius
• Magnetic field is symmetric: ( ) ( )B Bθ θ π= − +
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28Challenge the future
Rotating magnetic field
NNNNa == ∫π
θθθθ0
21 d)(;sin)(Sinusoidally distributed winding:
( ) d 2m
m g g
C
F H s H lθ τ= ⋅ =∫� �
�Ampere’s law:
θθθθθθπθ
θ
πθ
θ
cosdsind)(d)( 21
aaaa
S
m NiNiNiAnJFm
===⋅= ∫∫∫∫++
��
0
( )( ) d 2
2m
mm g g g
gC
FF H s l H B
l
θθ τ µ= ⋅ = ⇒ =∫� �
�
Demo SMWithOnePhase Demo Rotating3Phase
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Three pulsating fields
−−=−=
−−=−=
==
)cos()cos(ˆ)cos(),(
)cos()cos(ˆ)cos(),(
)cos()cos(ˆ)cos(),(
34
34
34
32
32
32
πωπθπθθπωπθπθθ
ωθθθ
tiNNitF
tiNNitF
tiNNitF
cmc
bmb
ama
−=−=
=
)sin()(
)sin()(
)sin()(
34
21
32
21
21
πθθπθθ
θθ
NN
NN
NN
c
b
a
−=
−=
=
)cos(ˆ)(
)cos(ˆ)(
)cos(ˆ)(
34
32
πωπω
ω
titi
titi
titi
c
b
a
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One rotating field
2 23 3
4 43 3
ˆ( , ) cos( )cos( )
ˆ( , ) cos( )cos( )
ˆ( , ) cos( )cos( )
ma
mb
mc
F t Ni t
F t Ni t
F t Ni t
θ θ ωθ θ π ω πθ θ π ω π
= = − − = − −
−++−=
−++−=
++−=
)cos(ˆ)cos(ˆ),(
)cos(ˆ)cos(ˆ),(
)cos(ˆ)cos(ˆ),(
38
21
21
34
21
21
21
21
πωθωθθ
πωθωθθωθωθθ
tiNtiNtF
tiNtiNtF
tiNtiNtF
mc
mb
ma
)cos(ˆ),(),(),(),( 23 tiNtFtFtFtF mcmbmams ωθθθθθ −=++=
)cos(4
ˆ3),(
2),( 00 t
l
iNtF
ltB
gms
gs ωθµθµθ −==
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31Challenge the future
Induction machines
• Introduction (5.1)
• Rotating magnetic field (5.2, also for SM)
• Why does an induction machine rotate?
• Induced voltage (5.3, also for SM)
• Definitions (5.4, 5.5)
• Equivalent circuits and voltage equations (5.7)
• Parameter identification (5.8)
• Performance characteristics (5.9)
• Power flow in three modes of operation (5.10)
• Speed control (5.13)
• Linear induction motors (5.16)
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Why does an IM work?
1 Sketch the flux linkage of dd’.
2 Sketch induced voltage in dd'.
The rotor turns dd’ and qq' are short-circuited via a large resistance Rr.
3 Sketch the current through dd'.
4 Sketch the flux density at the location of d’ B(π/2,t).
5 Sketch the flux density at the location of d' B(3π/2,t).
6 Sketch the torque on dd'.7 Sketch the torque on qq' in
the same way.
)cos(ˆ),( tBtBs ωθθ −=
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Results
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Conclusions
• constant torque with two turns
• at synchronous speed: no torque
• torque proportional to rotor frequency (slip frequency) if the
effect of the rotor currents on the field is negligible
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35Challenge the future
Induction machines
• Introduction (5.1)
• Rotating magnetic field (5.2, also for SM)
• Why does an induction machine rotate?
• Induced voltage (5.3, also for SM)
• Definitions (5.4, 5.5)
• Equivalent circuits and voltage equations (5.7)
• Parameter identification (5.8)
• Performance characteristics (5.9)
• Power flow in three modes of operation (5.10)
• Speed control (5.13)
• Linear induction motors (5.16)
Page 36
36Challenge the future
Overview Electrical Machines and
Drives
• 7-9 1: Introduction, Maxwell’s equations, magnetic circuits
• 11-9 1.2-3: Magnetic circuits, Principles
• 14-9 3-4.2: Principles, DC machines
• 18-9 4.3-4.7: DC machines and drives
• 21-9 5.2-5.6: IM introduction, IM principles
• 25-9 Guest lecture Emile Brink
• 28-9 5.8-5.10: IM equivalent circuits and characteristics
• 2-10 5.13-6.3: IM drives, SM
• 5-10 6.4-6.13: SM, PMACM
• 12-10 6.14-8.3: PMACM, other machines
• 19-10: rest, questions
• 9-11: exam