Title: Predefined Speed Control of BLDC Motor
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Predefined Speed Control of BLDC Motor
2Predefined Speed Control of BLDC Motor
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.
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3Predefined Speed Control of BLDC Motor
Block Diagram
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4Predefined Speed Control of BLDC Motor
Hardware Components
- 8051 series Microcontroller
- LCD
- Transformer
- Voltage Regulator
- Capacitors
- Resistors
- Diodes
- BLDC Fan
- EEPROM
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5Predefined Speed Control of BLDC Motor
Software Components
- Keil compiler
- Languages Embedded C or Assembly.
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6Predefined Speed Control of BLDC Motor
MICROCONTROLER
- 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.
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7Predefined Speed Control of 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
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8Predefined Speed Control of 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.
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9Predefined Speed Control of BLDC Motor
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.
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10Predefined Speed Control of 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.
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11Predefined Speed Control of 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
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12Predefined Speed Control of 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.
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13Predefined Speed Control of BLDC Motor
Control Circuit
- The HEX code generated is loaded into the
Microcontroller. - The controller used is AT89C52.
- The controller is operated at 11.059 MHz
frequency.
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14Predefined Speed Control of BLDC Motor
Motor Driver And Gate Driving Circuit
- 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.
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15Predefined Speed Control of BLDC Motor
Motor Driver And Gate Driving Circuit
- 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.
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16Predefined Speed Control of 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.
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17Predefined Speed Control of BLDC Motor
Converter circuit
- 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.
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18Predefined Speed Control of 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.
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19Predefined Speed Control of BLDC Motor
Working Principle
- 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.
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20Predefined Speed Control of BLDC Motor
Working Principle
- 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.
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21Predefined Speed Control of 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 switchings 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
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22Predefined Speed Control of BLDC Motor
Speed Control Of 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.
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23Predefined Speed Control of BLDC Motor
Speed Control Of 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
VoltageD Vin
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24Predefined Speed Control of 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.
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25Predefined Speed Control of BLDC Motor
SIMULATION RESULTS FOR VARIOUS PWM PULSES
- 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).
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26Predefined Speed Control of BLDC Motor
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.
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27Predefined Speed Control of 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.
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28Predefined Speed Control of 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.
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