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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]

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BLDC 전동기 드라이브 기초이론

Usage of Electrical Motors

-Courtesy of Emerson Comp.-

2/28


Category of Electrical Motors

3/28


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



Elementary DC motor with 3 commutator

segments and 2 brushes

Transistor inverter circuit for use

with 3-phase BLDCM

Commutation

5/28


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


Comparison

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Applications (I)

7/28



BLDC Motor (45kW)

BLDC Motor (24V, 250W)

Applications (II)

8/28



Applications (III)

9/28



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


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


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


Load Characteristics

Typical Speed / Torque Characteristics of Various Loads

13/28


Electrical Characteristics

aaat

fff

RtItEtV

RtItV

)()()(

)()(

a

PZkwherek

NZ

a

PtE erea

260)(

a

PZkwhereIkI

a

PZT tataem

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



)()(

)()()()(

)()(

)()(

)()()(

sss

ssJBsTsT

sIksT

sksE

sIsLRsEsV

rr

rLem

atem

rea

aaaat

dt

tdJtBtTtT

tiktT

tkte

tidt

dLtiRtetv

rrLem

atem

rea

aaaaat

))(()()()(

)()(

)()(

))(()()()(

Laplace Transformations

15/28



)()()( sT

kkBsJsLR

sLRsV

kkBsJsLR

ks L

etaa

aat

etaa

tr

)1(

1

)(

)()(

2,00)(

1

et

ma

et

mae

etaam

t

JJBetaa

t

sTt

r

kk

JRs

kk

JLsk

kksLRsJ

k

kkBsJsLR

k

sV

ssG

mL

e

emememesskssk

sG

m 11

1

1

1)(

21

.&. consttimeelectricalR

Lconsttimemechanical

kk

JR

a

ae

ET

am

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



.&. consttimeelectricalR

Lconsttimemechanical

kk

JR

a

ae

ET

am

Electrical Time Constant Mechanical Time Constant

17/28


Electrical Modeling

ccccbbcaacccc

bccbbbbaabbbb

accabbaaaaaaa

eiLiLiLdt

diRv

eiLiLiLdt

diRv

eiLiLiLdt

diRv

MLL

LLLL

LLLL

RRRR

cbbc

accaabba

sccbbaa

cba

c

b

a

c

b

a

s

s

s

c

b

a

c

b

a

e

e

e

i

i

i

dt

d

LMM

MLM

MML

i

i

i

R

R

R

v

v

v

0 0

0 0

0 0

acbcba MiMiMiiii 0

c

b

a

c

b

a

s

s

s

c

b

a

c

b

a

e

e

e

i

i

i

dt

d

ML

ML

ML

i

i

i

R

R

R

v

v

v

0 0

0 0

0 0

0 0

0 0

0 0

MLLLL scba

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


Operational Principles

• H1-Tr1 : controlling current through W1



• H1-Tr3

• H2-Tr1

• H3-Tr2

Counter-Clockwise Operation Clockwise Operation

3-Phase Unipolar Driven BLDCM

19/28


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






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

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Overall Output Characteristics

21/28


Low Cost Scheme: Unipolar Operation

2-Phase 4-Slot BLDCM 3-Phase 12-Slot BLDCM

Two-Phase BLDCM Three-Phase BLDCM

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4-Phase 16-Slot BLDCM 5-Phase 20-Slot BLDCM


Four-Phase BLDCM Five-Phase BLDCM

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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%








Performance Comparison

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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

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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


Phase Advance Angle=0° Phase Advance Angle=15°


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

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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)

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Phase-Advanced Angle=30° Phase-Advanced Angle=45°

Phase Angle + Extended Conduction Angle

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