Closed Loop Control for a Brushless DC Motor to Run at the Exactly Entered Speed

Closed loop control for a brushless dc motor to run at the exactly entered speed is a system that controls the BLDC (brushless dc) motor speed according to the user defined speed. In other words, this system runs the motor at 25%,50% or 75% of the total speed when user set this percentage of speed from digital keypad. Different variable speed drives are available in market which have been using different control techniques but here we have designed this system with the help of closed loop control technique. Normally to run the BLDC motor at desired speed is very difficult task but here we have made this so much easy with the help of this closed loop control for a BLDC motor to run at the exactly entered speed system. This system has designed with the help of, step down ac transformer, bridge rectifier, voltage regulator, LCD display, microcontroller pic18F452 belongs to pic family, MOSFET, speed sensors and OPTO isolator for driving the BLDC motor. It is less costly, more compact, controls the motor speed more precisely and effectively as compared to other system. The block diagram of this closed loop control for a brushless dc motor to run at the exactly entered speed system with all their essential components is shown is figure 1.

Block Diagram of Closed Loop Control for a Brushless DC Motor to Run at the Exactly Entered Speed System

Here is the block diagram of closed loop control for a brushless dc motor to run at the exactly entered speed system with all their essential components,

       Figure 1 Block Diagram of Closed Loop Control for a Brushless DC Motor to Run at the Exactly Entered speed.

Working of Closed Loop Control for a Brushless DC Motor to Run at the Exactly Entered Speed System:

This closed loop control for a brushless DC motor to run at the exactly entered speed system works on the principle of PWM (Pulse Width Modulation) control. In PWM control, the duty cycle of driving pulse is changed means pulse on or off time is changed. When this time is changed then output voltages are changed and by changing this output voltages BLDC motor speed is changed. This system is directly coupled with 230V ac, because this system consists of electronic components therefore these voltages are stepped down into 9 or 6V ac with the help of step down ac transformer. Then these voltages are converted into dc with the help of bridge rectifier and then regulated into 5V dc with the help of voltage regulator.

OPTO isolator and pic microcontroller are powered up with these regulated voltages. The pic microcontroller is the main controller of this system which efficiently and precisely control the motor speed. It is programmed in c language with the help of mikro/c software and is interfaced with keypad, OPTO isolator, LCD display and speed sensors. For running the BLDC motor at desired speed, the user will just press the keypad buttons. For example, the user wants to run the BLDC motor at 50% speed then he will just press the keypad button 5 and zero. By doing this, the microcontroller generates 50% duty cycle voltage pulse for BLDC motor then this voltage pulse drives the BLDC motor at 50% speed of the total speed. Similarly, the user can easily drive the motor at any desired speed. This desired speed is sensed by speed sensor and gives the logic signal to microcontroller then microcontroller displayed this speed at LCD display. So, the user can easily know the desired speed.

Application and Advantages of Closed Loop Control for a Brushless DC Motor to Run at the Exactly Entered Speed System:

1. By using this closed loop control for BLDC motor system, the user can easily run BLDC motor any speed.
2. This closed loop control for BLDC motor system could be used in drilling machines, lath machines, spinning machines, elevators and electric bikes.
3. This system controls the BLDC motor speed more efficiently and precisely as compared to other systems.
4. It is friendly to use no need of any expert person.
5. It is less costly as compared to other systems.