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BLDC 전동기 드라이버
시뮬레이션 실습
Presented by Byoung-Kuk Lee, Ph. D., Senior IEEE
Energy Mechatronics Lab. College of Information and Communication Eng.
Sungkyunkwan University
Tel: +82-31-299-4581 Fax: +82-31-299-4612 http://seml.skku.ac.kr EML: [email protected]
1/28
BLDC 전동기 드라이브 기초이론
Usage of Electrical Motors
-Courtesy of Emerson Comp.-
2/28
BLDC 전동기 드라이브 기초이론
Category of Electrical Motors
3/28
BLDC 전동기 드라이브 기초이론
DC Motors vs. BLDC Motors
DC Commutator Motor Brushless DC Motor
Motor
Structure
Synchro-
nization
Mechanical Switches
Brush and Commutator
Electric Switches
Semiconductor Switches and Hall Sensors
What is the BLDC Motor?
Commutator and slip ring are replaced by Electric Switches
Rotating field type (permanent magnet)
BLDC and PMAC
Rotor position detection → Hall sensors or optical sensors
4/28
BLDC 전동기 드라이브 기초이론
DC Motors vs. BLDC Motors
Elementary DC motor with 3 commutator
segments and 2 brushes
Transistor inverter circuit for use
with 3-phase BLDCM
Commutation
5/28
BLDC 전동기 드라이브 기초이론
DC Motors BLDC Motors
Basic Structure • rotating armature • rotating field
Rotor Position
Sensing
• mechanical position of brush • position sensor and logic circuit
Commutation • mechanical switching with brush and commutator
• electric switching by power semiconductor switches
Reverse Rotation • polarity change of applied voltage
• switching sequence change
Characteristics • east to control
• periodical maintenance
• mechanical noise
• lack of high speed operation due to use of brush and commutator
• large volume and complexity
• long time operation
• free of maintenance
• no mechanical noise
• high speed operation
• compactness and high density
• PM cost
• lack of field operation
DC Motors vs. BLDC Motors
Comparison
6/28
BLDC 전동기 드라이브 기초이론
DC Motors vs. BLDC Motors
Applications (I)
7/28
BLDC 전동기 드라이브 기초이론
DC Motors vs. BLDC Motors
BLDC Motor (45kW)
BLDC Motor (24V, 250W)
Applications (II)
8/28
BLDC 전동기 드라이브 기초이론
DC Motors vs. BLDC Motors
Applications (III)
9/28
BLDC 전동기 드라이브 기초이론
DC Motors vs. BLDC Motors
Electrical motor for submarines type Permasyn
Applications (IV)
10/28
Brushless DC Motors (BLDC)
DC Motors : Armature polarity change is performed by brush and commutator
BLDC Mission : Synchronized switching by power semiconductor switches based
on the information of rotor (permanent magnet) position
Trapezoidal Wave Operation : Back EMF is shaped of trapezoidal (quasi-square
wave) wave form
Characteristics : Similar to the separately excited field winding DC motor
BLDC 전동기 드라이브 기초이론
Classification: Driving Schemes
Permanent Magnet AC Motors (PMAC)
Synchronous Motors : Similar to the synchronous motor with wound rotor field
BLDC Mission : Synchronized switching by power semiconductor switches based
on the information of rotor (permanent magnet) position
Sinusoidal Wave Operation : Back EMF is shaped of sinusoidal wave form
(distributed winding)
Characteristics : Rotating field is similar to the induction motor or the synchronous
motor
11/28
BLDC 전동기 드라이브 기초이론
Classification: Rotor Types
Interior Rotor
Exterior Rotor
Slotless Type
High torque/inertia ratio
Rapid acceleration and
deceleration
Magnet retention
problem
Servo application
High inertia
Constant speed
Fan and blower
Minimized cogging torque
High speed
VCR & CD player
Type of axial-gap type motor
12/28
BLDC 전동기 드라이브 기초이론
Load Characteristics
Typical Speed / Torque Characteristics of Various Loads
13/28
BLDC 전동기 드라이브 기초이론
Electrical Characteristics
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22
Parameters
Ea : Back EMF [V] P : No. of Pole Z : No. of Total Conductors
: Flux Line per Pole [Wb] N : Revolution [rpm] ke : Back EMF Constant [Vs/rad]
a : No. of Parallel Circuit r : Rotor Angular Velocity [rad/s] Kt : Torque Constant [Nm/A]
Fundamental Equations of Permanent Magnet DC Motors
14/28
BLDC 전동기 드라이브 기초이론
Electrical Characteristics
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Laplace Transformations
15/28
BLDC 전동기 드라이브 기초이론
Electrical Characteristics
)()()( sT
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.&. consttimeelectricalR
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Closed-Loop Transfer Functions
Mechanical Time Constant : how quickly the speed builds up in response to a step change vt
Electrical Time Constant : how quickly the armature current builds up in response to a step change vt
16/28
BLDC 전동기 드라이브 기초이론
Electrical Characteristics
.&. consttimeelectricalR
Lconsttimemechanical
kk
JR
a
ae
ET
am
Electrical Time Constant Mechanical Time Constant
17/28
BLDC 전동기 드라이브 기초이론
Electrical Modeling
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Assumption
The motor is operated within the rated current, hence the motor is not saturated
Stator resistance of all the windings are equal and self and mutual inductances are
constant
Three phases are balanced and Iron losses are negligible
18/28
BLDC 전동기 드라이브 기초이론
Operational Principles
• H1-Tr1 : controlling current through W1
• H2-Tr2 : controlling current through W2
• H3-Tr3 : controlling current through W3
• H1-Tr3
• H2-Tr1
• H3-Tr2
Counter-Clockwise Operation Clockwise Operation
3-Phase Unipolar Driven BLDCM
19/28
BLDC 전동기 드라이브 기초이론
Operational Principles
S5
S6
b
c
S1
a
b
S6
S2
a
c
S1 S3
b
c
S2
S4
a
b
S3
a
c
S5
S4
Switching Signal of S1
Switching Signal of S4
Switching Signal of S3
Switching Signal of S6
Switching Signal of S5
Switching Signal of S2
Back EMF
Phase Current
Phase A
Phase B
Phase C
CB
(5, 6)AB
(1, 6)
AC
(1, 2)BC
(3, 2)
BA
(3, 4)
CA
(5, 4)CB
(5, 6)
30 90 150 210 270 330 (degree)
Detailed Switching Sequences
20/28
BLDC 전동기 드라이브 기초이론
Overall Output Characteristics
21/28
BLDC 전동기 드라이브 기초이론
Low Cost Scheme: Unipolar Operation
2-Phase 4-Slot BLDCM 3-Phase 12-Slot BLDCM
Two-Phase BLDCM Three-Phase BLDCM
22/28
BLDC 전동기 드라이브 기초이론
4-Phase 16-Slot BLDCM 5-Phase 20-Slot BLDCM
Low Cost Scheme: Unipolar Operation
Four-Phase BLDCM Five-Phase BLDCM
23/28
BLDC 전동기 드라이브 기초이론
Motors Turns/Phase Driving Scheme Max. Torque
(Nm)
Avg. Torque
(Nm)
Torque
Ripple
3-Ph 12 Slots 208 120º bipolar 0.4943 0.4632 13%
3-Ph 12 Slots 208 120º unipolar 0.3662 0.3272 23.7%
2-Ph 4 Slots 356 180º unipolar 0.5155 0.3968 151.4%
4-Ph 16 Slots 172 90º unipolar 0.3446 0.3230 19.6%
4-Ph 16 Slots 172 180º unipolar 0.4609 0.3436 65.8%
5-Ph 20 Slots 125 72º unipolar 0.2827 0.2606 17.5%
5-Ph 20 Slots 125 144º unipolar 0.3857 0.3471 22.4%
5-Ph 20 Slots 125 180º unipolar 0.4301 0.3506 42.4%
Low Cost Scheme: Unipolar Operation
Performance Comparison
24/28
BLDC 전동기 드라이브 기초이론
Field Weakening Operation
In the DC Commutate Motor with Separate Field Winding
Field-weakening is achieved by reducing the field current and thereby the field flux in
the machine
In the Brushless DC Motor
1) In principle, it is not possible for the drive to operate “above a base speed” in the
situation where the dc supply voltage and the back-EMF are equal
2) In BLDC motor, the source of field flux is permanent magnet and cannot be controllable
3) However, operation into the field-weakening region of a BLDC motor is possible by
adjusting the time-phase relationship between winding current and back-EMF
→ Phase-Advanced Angle Control
→ Extended-Conduction Angle Control
25/28
BLDC 전동기 드라이브 기초이론
Field Weakening Operation
Low Speed (100rpm) High Speed (3000rpm)
Problem on High-Speed Operation
1) The inductive reactance of the windings results in a significant time constant
2) The time taken for the current to reach its rated value is large and it reaches the rated
value at the end of the interval
26/28
BLDC 전동기 드라이브 기초이론
Phase Advance Angle=0° Phase Advance Angle=15°
Field Weakening Operation
Phase Advanced Angle Control
1) Turning-on each phase earlier
the current rise is faster, since the applied voltage is counteracted by a lower EMF
2) Turn-off Instant can be problem
27/28
BLDC 전동기 드라이브 기초이론
Field Weakening Operation
120° Conduction Angle (100rpm) 180° Conduction Angle (100rpm)
Extended Conduction Angle Control
Each winding is switched off before the corresponding back-EMF has fallen to zero
Extend the interval (Extended-conduction angle)
28/28
BLDC 전동기 드라이브 기초이론
Field Weakening Operation
Phase-Advanced Angle=30° Phase-Advanced Angle=45°
Phase Angle + Extended Conduction Angle