brushless dc motor

Brushless DC Motor Application, Pros and Cons

(Last Updated On: April 16, 2021)

Brushless DC motor has been the heart of automobiles for a long. On a typical brushless DC motor, there is a permanent magnet on the outside and a spinning armature inside. Permanent magnets are stationary, so they are called stators. The armature is rotated, so it is called a rotor.

Armor has an electronic magnet. When you run electricity into this electronic magnet, a Brushless DC motor, it creates a magnetic field in the armature that attracts and deflects the magnet in the stator.

So the armor spins with 180 degrees. To turn it around, you’ll need to change the poles of the electronic magnet.

Brushes handle this change at the pole. They interact with the two spinning electrodes attached to the armature and then invert the magnetic pole of the electromagnet.

Brushless DC motor challenges

This setup is effective and easy to produce and inexpensive, but there are several problems:

Brushes eventually wear out.

You will find sparking and electric noises as the brushes are making/breaking connections

Brushes limit the maximum speed of the motor.

The electronic magnet in the center of the motor makes it hard to cool.

The use of brushes limits the number of poles in the armature.

With the advent of cheaper computers and power transistors, it was possible to “turn the motor inside” and remove the brushes.

On the brushless DC motor (BLDC), you place a permanent magnet on the rotor and you move the electromagnet to the stator.

Brushless DC motor advantages

Then you use a computer (connected to a high-power transistor) to charge the electronic magnets as the shaft turns. This system has all kinds of advantages:

Since a computer controls the motor rather than mechanical brushes, it is more precise. The computer can also factor in the speed equation of the motor.

This makes brushless motors more efficient.

No sparking and much less electrical noise.

There is no brush to wear.

With electronic magnets in the stator, they are very easy to cool.

Your stator may contain a lot of electronic magnets for more precise control.

A brushless DC electric motor (BLDC motor or BL motor), also known as an electronically transmitted motor (ECM or EC motor) and synchronous DC motor, synchronous motors are powered by direct current (DC) electricity through an inverter or switching power supply.

Optional current (AC) to drive each episode of the motor through a closed-loop controller. The power controller in the form of the current provides pulses in the motor winding which controls the speed and torque of the motor.

Brushless vs brushed motor

Brushed DC motors were invented in the 19th century and are commonplace. Brushless DC motors were made possible by the development of solid-state electronics in the 1960s.

The torque of rotating magnets connected to an electric motor rotor develops torque by rotating the rotating part of the machine and the stationary magnet.

One or both sets of magnets are electromagnets, made of wires harsh around the iron core.

Running through wire winding creates a magnetic field in DC, which provides the power that drives the motor.

However, each time the rotor rotates by 180 ° (a half-turn), the position of the north and south poles of the rotor is reversed.

If the polar magnetic fields of the poles are the same, it will cause the torque to crash on the rotor at each half-turn, and so the average torque will be zero and the rotor will not rotate. Each 180 ° has to be reversed with a rotor turn (or it will stop when it is on the wrong side).

This is the opposite of the direction of the magnetic field such as the end of the rotor, so the torque of the rotor is always in the same direction.


On brushed motors invented in the nineteenth century, it was called a passenger with a rotation switch on the motor shaft.

It consists of a rotating cylinder divided into multiple metal contact sections on the rotor.

The sections are connected to the rotor by an electromagnetic winding wire.

Two or more fixed contacts, called “brushes” made of soft conductors such as graphite, press against the commutator, sliding the electrical contact into the parts continuously as the rotor turns, providing electric current to the windings.

Each time the rotor rotates 180 by, the opposite side of the electric current in the electric current provided by the commutator, so the magnetic field produces a torque on one side.

Travelers’ Difficulties

There are many engineering disadvantages of movement that have led to the reduction of the use of brush motors. The disadvantages are:

The friction of sliding brushes with rotating transport parts causes a loss of power which can be significant in a low power motor.

The soft brush material goes underneath due to friction, creating dust and eventually the brushes have to be replaced.

This makes changing motors inappropriate for low particulate or sealed applications, such as hard disk motors, and for applications that require a maintenance-free operation.

Resistance to the contact of the sliding brush results in a brush drop called a voltage drop in the motor circuit that receives power.

Frequent switching of currents through the opening of the windings triggers the contact of the contactors, which may be due to the risk of fire in the explosive atmosphere, the source of degraded UV radiation, and the source of the electronic noise, which may be due to the nearby micro-electronic electronic circuits.

During the last hundred years, high-power DC brush motors were once replaced by modified Current (AC) synchronous motors as the mainstay of the industry.

Currently, brushed motors are used only in low power applications or where DC is available only, but the above drawbacks limit their use even in these applications.

A brushless motor was invented to solve these problems.

Brushless solution

The development of semiconductor electronics in the 1970s allowed the elimination of passengers and brushes on DC motors.

In a brushless DC motor, an electronic servo system replaced mechanical transport communications.

An electronic sensor detects the angle of the rotor and controls the semiconductor switches, such as transistors that change currents with winding, either reverse the direction of the current or rotate each 180 ° shaft at the correct time on a motor, making the electromagnet torque to one side.

Elimination of sliding contacts allows brushless motors less friction and longer lifespan; Their career is limited to the lifetime of their bearings only.

Brushed DC motors develop maximum torque while remaining stable, decreasing linearly as the speed increases.

Some limitations of brushless motors may be overcome by brushless motors; These include high efficiency and low sensitivity for mechanical wear.

These benefits come at the expense of potentially less rugged, more complex and more expensive control electronics.

A simple Brushless DC motor has a permanent magnet that rotates around a fixed armature and eliminates problems associated with the current’s connection to the moving armature.

An electronic controller replaces the brush / brushed DC motor’s broad / commutator assembly, which switches the phase on a continuous winding to rotate the motor.

The controller distributes power over a similar time period using a solid-state circuit instead of a brush/passenger system.

Brushless DC motor offers a variety of advantages, including brighter DC motors, higher torque to weight ratio, more torque per watt (efficiency increase), elongation, reduction, longer lifespan (no brush and passenger decay), emitting sparks from commutators, and electromagnetic interference (EMI). ) Overall reduction.

Because there is no air in the rotor, they do not face centrifugal forces, and since the windings are supported by the housing, they can be cooled by conduction, requiring no airflow inside the motor to cool.

Instead, it means that the interior of the motor is completely enclosed and can be protected from dirt or other foreign matter.

Brushless DC motor transport can be applied to software using a microcontroller or microprocessor computer, or alternatively to analog hardware or digital firmware using field-programmable gate array (FPGA).

Limiting travel speed through electronics instead of brushes, “micro-stepped” operation for slow and / or fine speed control, and a holding torque when fixed does not provide greater flexibility and power with brushed DC motors.

The controller software is customizable to the specific total used in the application, thus creating greater transport efficiency.

The highest power that can be applied to brushless motors is almost exclusively limited by heat; Too much heat weakens the magnet and damages the insulation of the air.


Four poles on the two-phase brushless motor stator. It’s part of a computer cooling fan; The rotor has been removed.

Brushless DC motor performs many functions originally performed by brushed DC motors, but cost and control complexity prevents brushless motors from completely replacing brush motors in the least expensive regions.

Nevertheless, Brushless DC motors dominate many applications, especially devices such as computer hard drives and CD / DVD players.

In electronic equipment, the small cooling fan is operated exclusively by the Brushless DC motor. These can be found on cordless power tools where the increased efficiency of the motor leads to longer use before the battery is charged.

A low-speed, low-power Brushless DC motor is used on the direct-drive turntables for gramophone records.


Brushless DC motor is available in electric vehicles, hybrid vehicles, and personal transporters wheels. The same principle applies to self-balancing scooter wheels. Most electric-powered RC models use brushless motors because of high efficiency.

Cordless equipment

Brushless DC motor is available in a number of modern cordless tools, some of which include string trimmers, leaf blowers, saws (round or reciprocating) and drills/drivers.

The advantage of brushless over brushed motors (low weight, high efficiency) is that battery operated equipment for the handheld is more important than fixed equipment plugged into an AC outlet, so uptake in that part of the market has been accelerated.

Heat and ventilation

The heating, ventilation and air conditioning (HVAC) and refrigeration industries have a tendency to use brushless motors instead of different types of AC motors.

The most significant reason for switching to a brushless motor is the dramatic reduction of power to operate them versus a typical AC motor.

The shaded pole and adjustable split capacitor motor once dominated the fan motor, now many fans operate using brushless motors Also use some fanless brushless motors to improve overall system efficiency.

In addition to the high efficiency of brushless motors, HVAC systems (typically featuring variable-speed and / or load modulation) use brushless motors because the built-in microprocessor allows programmability, control over airflow, and serial communication. Some ceiling fans and portable fans also feature this motor.

They advertise the motor is higher energy efficient and quieter than most fans.

Industrial engineering

The application of Brushless DC motor in industrial engineering focuses primarily on manufacturing engineering or industrial automation design.

In manufacturing, brushless motors are mainly used for speed control, positioning or acquisition systems.

Brushless motors are ideally suited for production applications due to their high power density, good speed-torque properties, high efficiency, wide speed range and low maintenance.

The most common uses for brushless DC motors in industrial engineering are linear motors, servomotors, actuators for industrial robots, extruder drive motors and feed drives for CNC machine tools.

brushless dc motor

Speed ​​control system

Brushless DC motors are commonly used in regular or variable-speed applications such as pumps, fan and spindle drives because they are capable of developing high torque with good speed response.

Also, they can easily be automated for remote control. Due to their construction, they have good thermal properties and high power efficiency.

Brushless DC motors include an electronic motor controller and a rotor position response sensor in an electronic machine to achieve a variable speed response.

Brushless DC motors are widely used as servomotors for machine tool servo drives. Servomotors are used for mechanical displacement, positioning or precise speed control. DC stepper motors can also be used as servomotors.

But since these are operated with open-loop control, they usually show torque vibration.

Brushless DC motors are more suitable as servomotors because their precise speed is based on a closed-loop control system that provides tightly controlled and stable operation.

Positioning and Actuation Systems

The Brushless DC motor industry is used in positioning and actuation applications.

Brushless steppers or servo motors for assembly robots are used for any part of the assembly or a tool in the manufacturing process, such as welding or painting.

The advantage of linear motors, called linear motors, that produce linear speeds is that they can generate linear motion without the need for transmission systems such as ballscrews, leadscrew, rack-and-pinion, cam, gears or belts, which are required for rotary motors.

Transmission systems introduce low responsiveness and reduced accuracy Known direct drive, brushless DC linear motors have a slotted stator with magnetic teeth and a movable actuator, with permanent magnetic and coil windings.

To achieve linear motion, a motor controller stimulates coil windings on the actuator, causing an interaction of magnetic fields as a result of linear motion.

Tubular Linear Motor is the other type of linear motor design operated in the same way.


A microprocessor-controlled BLDC motor drives a micro-radio-controlled aircraft. This external rotor motor weighs 5 grams and weighs about into the kilowatt output range.

Brushless motors have become a popular motor choice for model planes, including helicopters and drones.

Due to their optimum power to weight ratio and wide range of available sizes, motors up to a kilowatt output range larger than 5 grams have revolutionized the market for electric-powered model flights, often replacing virtually all brushed electric motors, often with toy-grade aircraft for less powered cheaper.

They encouraged the development of a simpler, lightweight electric model aircraft than previous internal combustion engines to strengthen larger and heavier models.

The increased power-to-weight ratio of modern batteries and brushless motors allows models to rise vertically rather than climb slowly, due to the lack of noise and mass compared to smaller combustion fuel internal combustion engines, which is another factor in their popularity.

Legal restrictions on the use of combustion engine-powered model planes in some countries, often due to the possibility of noise pollution – even almost all model engines have been available in recent decades – have also favored higher transfer power systems.

Radio-controlled cars

Their popularity has also increased in radio-controlled (RC) car areas. Brushless motors have been legal in North American RC car racing since 2006, according to Radio Operated Auto Racing (ROAR).

These motors provide a lot of power for RC racers and if appropriate gearing and high-discharge lithium polymer (Li-Po) or lithium iron phosphate (LiFePO4) batteries. These cars can achieve speeds of up to 160 kilometers (99 miles) per hour.

A brushless DC motor is capable of producing more torque and has faster pick rotation speeds than nitro- or petrol-powered engines.

Nitro engines are about 46,800 R / min and top of 2.2 kW (3.0 hp), while a small brushless motor can reach 50,000 R / min and 3.7 kW (5.0 hp).

A larger brushless DC motor can reach 10 kW (13 hp) and 28,000 r / min to power one-fifth-scale models.

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