Predefined Speed Control of BLDC Motor

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Predefined Speed Control of BLDC Motor
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Predefined 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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Predefined Speed Control of BLDC Motor
Block Diagram
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Predefined Speed Control of BLDC Motor
Hardware Components

• 8051 series Microcontroller
• LCD
• Transformer
• Voltage Regulator
• Capacitors
• Resistors
• Diodes
• BLDC Fan
• EEPROM

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Predefined Speed Control of BLDC Motor
Software Components

• Keil compiler
• Languages Embedded C or Assembly.

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Predefined 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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Predefined 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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Predefined 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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Predefined 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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Predefined 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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Predefined 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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Predefined 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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Predefined 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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Predefined 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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Predefined 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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Predefined 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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Predefined 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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Predefined 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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Predefined 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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Predefined 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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Predefined 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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Predefined 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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Predefined 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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Predefined 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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Predefined 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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Predefined 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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Predefined 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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Predefined 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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