BLDC -Motor




  • BLDC stands for Brushless DC motor.
  • semiconductor control is used for controlling the statas current in such a way that maximum torque is obtained at a given speed.


Stators has three-phase winding while the rotor is in the form of a permanent magnet:

BLDC Motor also consist of rotor position sensors that produce an electrical signal that indicates the current position of the rotor.

BLDC stator winding is driven from an electronic drive which is 3- phase inverter.

The speed of BLDC can be controlled by controlling its stator voltage which can be achieved by controlling the DC input voltage of the inverter.


The document magnet Brushless DC motors use a hall sensor with 60-degree electrical spacing.


  • These sensors produce a logic 1 when exposed to N- type of the rotor and logic 0 otherwise.


  • The driver circuit operate on DC supply.
  • The fields produced by stator & rotor remains stationary with respect to each other.
  • This motor does not have Brushless motor.


  • Unipolar ( half wave) BLDC motor.
  • Biopolar ( full wave ) BLDC motor.


BLDC motor works on the principle similar to that of a conventional DC motor, i.e the Lorentz force law which states that whenever a current carrying conductor placed in a magnetic field it experiences a force.As a consequence of reaction force, the magnet will experience an equal and opposite force.BLDC motor, the current carrying conductor is stationary while the permanent magnet moves.

When the stator coils are electrically switched by a supply source,it becomes electromagnet and starts producing the uniform filled in the air gap.though the source of supply is DC, switching makes to generate an AC voltage waveform with trapezoidal shape.Due to the force of interaction between electromagnet stator and permanent magnet rotor,the rotor continues to rotate.motor stator is excited based on different switching states,with the switching of windings as high and low signals, corresponding winding energized as North and South poles.the permanent magnet rotor with north and south poles align with stator poles causing motor to rotate.

Observe that motor produces torque because of the development of attraction forces ( when north- south or south- north alignment) and repulsion force ( when north-north or south-south alignment).by this way motor moves in a clockwise direction.


  • No maintenance is required due to absence of Brushes and commutators.
  • Low inertia due to low friction.
  • Higher maximum speed due to low friction.
  • Long life.
  • Reliable operation.
  • High efficiency ( more than 75%).
  • Speed and position can be controlled.


  • Complex construction.
  • Expensive.
  • Need complex electronic controllers.


circuit diagram for Arduino bldc and esc controller

Arduino Code For BLDC

        Arduino Brushless Motor Control

#include <Servo.h>

Servo ESC;     // create servo object to control the ESC

int potValue;  // value from the analog pin

void setup() {
  // Attach the ESC on pin 9
  ESC.attach(9,1000,2000); // (pin, min pulse width, max pulse width in microseconds) 

void loop() {
  potValue = analogRead(A0);   // reads the value of the potentiometer (value between 0 and 1023)
  potValue = map(potValue, 0, 1023, 0, 180);   // scale it to use it with the servo library (value between 0 and 180)
  ESC.write(potValue);    // Send the signal to the ESC

working video


  • Electric power steering.
  • Air conditioners.
  • In aerospace.
  • Computer peripheral equipments.
  • Instrumentation and control systems.
  • Biomedical instrumentation.

15140cookie-checkBLDC -Motor

Author: yawot

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