Predefined speed control of bldc motor

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Predefined Speed Control of
BLDC Motor

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Introduction
 The aim of the project is to control the speed of a BLDC motor using a
microcontroller with the help of SVPWM-technique. A brushless DC
(BLDC) motor drive is characterized by higher efficiency, lower
maintenance, and higher cost. Therefore, it is necessary to have a low-
cost but effective BLDC motor controller. Based on the principle of
PWM, speed of the motor can be controlled.
BLDC Motor

Block Diagram
BLDC Motor

Hardware Components
 8051 series Microcontroller
 LCD
 Transformer
 Voltage Regulator
 Capacitors
 Resistors
 Diodes
 BLDC Fan
 EEPROM
BLDC Motor

Software Components
 Keil compiler
 Languages: Embedded C or Assembly.
BLDC Motor

MICROCONTROLE
R
The AT89C52 is a low-power, high performance CMOS 8-bit
microcomputer with 8Kbytes of Flash programmable and erasable
read only memory (PEROM).
The on-chip Flash allows the program memory to be reprogrammed
in system or by a conventional nonvolatile memory programmer.
BLDC Motor

Features
 8K Bytes of In-System Reprogrammable Flash Memory
 Endurance: 1,000 Write/Erase Cycles
 Fully Static Operation: 0 Hz to 24 MHz
 Three-level Program Memory Lock
 256 x 8-bit Internal RAM
BLDC Motor

BLDC
Motor
 The BLDC motor is an AC synchronous motor with permanent
magnets on the rotor (moving part) and windings on the stator (fix
part).
 Permanent magnets create the rotor flux and the energized stator
windings create electromagnet poles.
 The rotor is attracted by the energized stator phase.
BLDC Motor

 By using the appropriate sequence to supply the stator phases, a
rotating field on the stator is created and maintained.
 The lead between the rotor and the rotating field must be controlled
to produce torque and this synchronization implies knowledge of the
rotor position.
BLDC
Motor
BLDC Motor

Principle of BLDC
Motor
 Frequency inverter used as Commutator.
 Commutation depends on rotor position.
 Speed control by motor voltage.
 Angle between mmfs of a stator and rotor is fixed to 90
degree.
 Motor behaves like a DC Motor.
 No commutation occurs on spinning shaft.
BLDC Motor

Circuit Operation
The operation of the circuit can be explained in three parts.
 Control circuit
 Motor driver and Gate driving circuit
 Converter circuit
BLDC Motor

Control Circuit
 Control circuit gives out the switching signals to the converter
bridge.
 A microcontroller is dedicated to generate the switching pulses.
 The microcontroller is programmed to give out pulse according to
SVPWMM technique.
 Program is compiled in Keil software.
BLDC Motor

 The HEX code generated is loaded into the Microcontroller.
 The controller used is AT89C52.
 The controller is operated at 11.059 MHz frequency.
Control Circuit
BLDC Motor

 Instead of using an inverter and a regulator we have used a motor driver
HW30A which acts as inverter to supply the voltage for the Motor.
 HW30A is an inbuilt Inverter which is having Inverter circuit as well as
MOSFET Driver circuit.
 We are using this type of technique because of on using general
inverter.
Motor Driver And Gate Driving Circuit
BLDC Motor

 We are facing the difficulties like large Heat dissipation, so that this
heat would cause a heat sinking problem which in turn results in
the failure of the Inverter.
 By using this motor driver the circuit complexity is reduced and the
heat dissipation problem, is also reduced.
Motor Driver And Gate Driving Circuit
BLDC Motor

Converter Circuit
 The converter circuit is provided by the Motor driver.
 The D.C supply is fed through a bridge rectifier.
 The switches in the Motor driver are turned ON and OFF as per the
program.
 The rectifier circuit is made of diodes.
 The component used is IN4007 which is capable of blocking a reverse
voltage of 1000 V DC and can carry a current of 10A continuous.
BLDC Motor

 All these components are placed on General PCB.
 Control circuit and gate driving circuit components are soldered
directly on the Pcb.
 Whereas, the power components as connected with suitable
connectors as they carry larger currents.
Converter circuit
BLDC Motor

Working
 The basic construction of a brushless dc consists of a fan blade attached
to a permanent magnet rotor that surrounds the electromagnetic coils
of the stator and associated control electronics.
 A typical biphase brushless fan motor is made from a permanent
magnet rotor assembly that surrounds four electromagnetic coils.
 The coils work in pairs, with coils A and C forming one phase
and coils B and D the other phase.
BLDC Motor

 A Halleffect sensor monitors rotor position, providing feedback to the
embedded MCU for commutation, speed regulation, and fault detection.
 Commutation between the two phase windings in the dc fan takes place
electronically by alternately applying power to L1 and L2.
 Dead zones between the power pulses limit current for speed control
and helps minimize a cogging effect when the rotor magnets align with
the stator coils.
 The on and off power of the commutation period resembles the output
from a pulse width modulator.
Working Principle
BLDC Motor

 The MCU uses a PWM to control the period of the motor drivers and,
thus set fan speed.
 Feedback from the Hall sensor monitors actual fan rpm and indicate
when communication should take place.
 The MCU continuously monitors motor speed by measuring the output
period of the Hall effect sensor.
 A period that run shorter than the target length indicates motor speed
is too fast.
Working Principle
BLDC Motor

Speed Control Of BLDC Motor
 Pulse width modulation is a commonly used technique for controlling
power to an electrical device.
 The PWM switching frequency has to be much faster than what would
affect the load.
 Typically switching’s have to be done several times a minute in an
electric stove, 120 Hz in a lamp dimmer, from few kilohertz (kHz) to
tens of kHz for a motor drive and well into the tens or hundreds of kHz
in audio amplifiers and computer power supplies
BLDC Motor

 The term duty cycle describes the proportion of on time to the regular
interval or period of time.
 A low duty cycle corresponds to low power, because the power is off for
most of the time.
 Duty cycle is expressed in percent, 100% being fully on.
 The main advantage of PWM is that power loss in the switching devices
is very low.
BLDC Motor

 When a switch is off there is practically no current and when it is on,
there is almost no voltage drop across the switch.
 Power loss, being the product of voltage and current, is thus in both
cases close to zero.
 The desired speed can be obtained by changing the duty cycle.
 The PWM in microcontroller is used to control the duty cycle of DC
motor.
Average Voltage=D * Vin
BLDC Motor

SIMULATION RESULTS FOR VARIOUS PWM
PULSES
 The speed control technique employed here is pulse width modulation
(PWM) technique.
 The duty cycle determines the speed of the motor
Average voltage = D * Vin
 The average voltage obtained for various duty cycles is also mentioned
and as the duty cycle percentage decreases average voltage also
decreases from the supply voltage.
BLDC Motor

 Duty cycle is defined as the percentage of time the motor is ON.
 Therefore, the duty cycle is given as
Duty Cycle = 100% x Pulse Width/Period
Where,
Duty Cycle in (%)
Pulse Width = Time the signal is in the ON or high
state(sec)
Period = Time of one cycle (sec).
BLDC Motor
SIMULATION RESULTS FOR VARIOUS PWM
PULSES

Applications
 BLDC motors fulfill many functions originally performed by brushed
DC motors.
 Cost and control complexity prevents BLDC motors from replacing
brushed motors completely in lowest cost areas.
 High power BLDC motors are found in electric vehicles and hybrid
vehicles.
BLDC Motor

Advantages
 Voltage and current rating is high.
 High speed can be achieved.
 As there is no brushes it requires no servicing.
 There is no sparking & less electrical noise.
BLDC Motor

Conclusion
 The hardware for closed loop control of BLDC motor using
microcontroller is designed. By using the PWM technique speed of
the BLDC motor was controlled and it was made to run at exactly
entered speed. In future this hardware will be implemented and
the speed control will be observed.
BLDC Motor

Predefined speed control of bldc motor

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