OFBLDC MOTOR

SPEED CONTROL

K. Sai Srikanth

BE 4/4(EEE)

1005-10-734038

Presented By

Under the supervision of..

Mr. M. V. Ramana Rao

Assistant professor

EED, UCE(A), OU

CONTENTS

Significance of BLDC motor and its veteran applications

Construction, working and analysis

Demerits of usage

Speed control of BLDC motor - briefing

Digital Signal Processing (DSP) speed control

Our future endeavors

PWM speed control

CONSTRUCTION

Stator may be a conventional 3-Ø winding or armature winding of DC motor

Power circuit

Rotor may be a permanent magnet or a electromagnet

Control Circuit Power electronic circuit in inverter configuration Rotor shaft position sensor Electronic timing device

Supply Circuit Full wave diode rectifier

Supply Circuit Control Circuit

Power Circuit

N

S

R

B

Y

1-Ø AC supply

D1

D2D3

D4

CS3 S2 S1

Electronic timing device

Rotor position sensor

WORKING

\\

N

S

Y

R

B

Y’

R’

B’

WORKING

ANALYSIS Instantiating the rotor to be displaced by Ɵ wrt phase R

Electromagnetic torque, TeR = k * iR * sin(Ɵ)

Similarly, TeY = k * iY * sin(Ɵ-120)

And, TeB = k * iB * sin(Ɵ+120)

The instantaneous currents in the phases

iR = IM * sin(Ɵ)

iY = IM * sin(Ɵ-120)

iB = IM * sin(Ɵ+120)

IM is the maximum current flowing in a phaseContd…...

The resultant torque Te = 1.5 * k * Im

Substituting… TeR = k * Im * sin2(Ɵ)

Similarly, TeY = k * Im * sin2(Ɵ-120)

And, TeB = k * Im * sin2(Ɵ+120)

The resultant torque, Te = TeR + TeY + TeB

On solving,

CONCLUSIONS

Resultant torque of BLDC motor is independent of rotor position angle

Hence by, torque can be controlled by varying the amplitude of phase winding currents

Henceforth, speed can be controlled by varying the current flow in to the phases

HALL EFFECT SENSOR

A 3-pin Transducer

Varies its output voltage in response to magnetic field

Proximity, positioning, speed detection current sensing applications

SIGNIFICANCE OF BLDC Absence of mechanical commutator and brushes

Longer period of life and efficient operation

Minimal electromagnetic interference

Rapid response even when submerged in fluids

Hybrid of synchronous motor and brushed DC motor

Low risk of explosion, Little maintenance

More torque to weight ratio

APPLICATIONS OF BLDC Robotics

Air crafts and satellite systems

Miniature applications Turn table drives for record players

Hard disk drives for computers

Low cost instruments

Small fans for cooling electronic equipment

Road Transportation

Motor drive-load control systems

Power factor improvement

DEMERITS

High installation cost

Requirement of the skilled for operation and maintenance

Complexity in design

Absence of continuous duty as in 3-Ø induction motor

RATINGS OF THE BLDC DRIVE

Motor Rating 1.2 HP 3 HP

Voltage 380 V 380 V

Rotor inertia 1.28 kg.cm2 2.8 kg.cm2

Torque constant 0.61 Nm/A 0.61 Nm/A

Peak torque 6 Nm 14 Nm

Max. Coupling torque 0.06 Nm 0.013 Nm

Max. Speed 6000 rpm 6000 rpm

Nominal Torque 1.25 Nm 3.2 Nm

Nominal Power 0.4 kW 1.0 kW

Feed back 3 V 3 V

SPEED CONTROL OF BLDC

Conventional methods

Field control

Stator flux control

Non-conventional/special methods

PWM method of control

DSP method of control

Tedious operation, involves losses

Flexible operation, Better scope of control, High η

DSP SPEED CONTROL

μ – 2407 chip

Comprises registers and flags for storing and processing the memory

The inverter switching sequence is encoded is into the registers

BLOCK DIAGRAM

Diode Rectifier Inverter

RotorShaft

Sensor

Feedback

1-ØAC SUPPLY

DSPController

TmωM

PULSE WIDTH MODULATION

PWM CONTROL

Varying the amplitude of the carrier wave the desired pulse width is obtained

Hence by, current pulses of varying magnitude(i.e., different pulse widths) are fed to the stator

Henceforth, the torque is varied and controlled desirably

SIMULATION

Depicting the desired response considering a virtual model

Software packages

PWM speed control of the virtual BLDC drive is achieved

OUR FUTURE ENDEAVORS

To study the interfacing of the BLDC drive to the DSP

Achieving the speed control and recording the results

Creating the virtual BLDC drive using MATLAB - SIMULINK

Simulating the speed response by the method of PWM control

Verifying and contrasting the characteristics from the two methods

APPLICATIONS

REFERENCES

GENERALISED THEORY OF ELECTRICAL MACHINES, Dr. P.S. Bimbhra

THEORY AND PERFORMANCE OF ELECTRICAL MACHINES, J.B. Gupta

SPEED CONTROL OF BLDC MOTOR USING MICRO-2407, Vi Microsystems pvt ltd

WIKIPEDIA - en.wikipedia.org

Queries.......

Thank You....