Spis treści:
A motor converts supplied electrical energy into mechanical energy. Various types of motors are in common use.
Brushless DC (BLDC) motors have high efficiency and excellent controllability and are widely used in many applications.
Brushless motor vs. brush motor - a comparison
It is impossible not to start with this important distinction. Increasingly, we are seeing in use BLDC motors, which in many spheres are displacing brush motors from use and replacing the mechanisms that have accompanied us for more than a century. Let’s start with the construction of both motors.
A brush motor consists of:
- Stator – an external component, surrounding the rotor and containing magnets with a constant magnetic field.
- Windings – wound on the rotor, when current flows, they “behave” like magnets and produce a magnetic field.
- Rotor – rotates around its own axis during operation.
- Brushes – are located at the rotor axis and provide electrical contact with the commutator.
- Commutator – switches the direction of current in the windings, thus changing the poles of the magnetic field.
When an electric charge flows through the windings, a magnetic field is then created.
The field created by the winding interacts with the field of magnets in the stator, and the unidirectional poles repel each other, setting the rotor in motion. It rotates from its starting position by 180 degrees, and its further rotation requires reversing the magnetic field. This is made possible by a commutator that moves along with the rotor. By switching the direction of the current in the winding, the magnetic field is reversed, allowing a full 360-degree rotation.
As for the structure and operation of a BLDC motor, it is somewhat the opposite of a brush motor. Permanent magnetic field magnets are placed on the rotor, while the windings are located in the motor’s stator and form coils. The influx of charge changes the magnetic field on the coils setting the rotor in motion. This solution means that there is no need for a commutator and brushes in the motor, as we do not need to transfer current to the rotor. The operation of a brushless motor requires a controller that precisely controls the direction and intensity of the electric charge flow.
Brushless motor - what is it?
Engineers face the challenge of designing electrical equipment to perform mechanical tasks, and their first step is to consider how electrical signals are converted into energy.
Motors are among the devices that convert electrical signals into motion, that is, they exchange electrical energy for mechanical energy.
As the name suggests, brushless DC motors DC do not use brushes.
In brush motors, these brushes deliver current through the commutator to the coils on the rotor.
So how does a brushless motor transmit current to the coils on the rotor?
This is not the case, because the coils are not located on the rotor.
Instead, the rotor is a permanent magnet – the coils do not rotate, but instead are fixed in place on the stator.
Since the coils do not move, there is no need for brushes and a commutator.
With a brush motor, rotation is achieved by controlling the magnetic fields generated by the coils on the rotor, while the magnetic field generated by the stationary magnets remains constant. To change the speed, the voltage of the coils must be changed.
In the case of a BLDC motor, the permanent magnet rotates; rotation is achieved by changing the direction of the magnetic fields generated by the surrounding stationary coils. To control the rotation, we adjust the magnitude and direction of the current in these coils.
Advantages of BLDC brushless motors
The first advantage of a brushless motor is improved efficiency. BLDC motors can steer continuously at maximum rotational force (torque), while brush motors achieve maximum torque only at certain pivot points. For a brush motor to provide the same torque as a brushless model, it would have to use larger magnets. Therefore, even small BLDC motors can deliver significant power.
The second major advantage – related to the first – is controllability. BLDC motors can be controlled by feedback mechanisms to provide exactly the desired torque and speed. Precise control, in turn, reduces energy consumption and heat generation, and in the case of battery-powered motors, extends their life. Because they don’t use brushes, BLDC motors also offer long life and low electrical noise.
In brush motors, the brushes and commutator wear out due to constant moving contact, and also produce sparks at the point of contact. In particular, electrical interference is the result of strong sparks, which are usually generated in areas where the brushes pass through gaps in the commutator. For this reason, BLDC motors are often considered preferable in applications where avoiding electrical interference is important.
Applications for BLDC brushless motors
We know that BLDC motors offer high efficiency and controllability, as well as long life. So what are they suitable for?
Because of these essential strengths , they are widely used in continuous-mode appliances. They have long been used in washing machines, air conditioners and a wide range of electronic equipment – they are also increasingly appearing in fans, where their high efficiency contributes to a significant reduction in energy consumption.
In addition to the home appliances and small electronics sectors, they can be found in electric vehicles such as cars, motorcycles, scooters and scooters. In aviation, especially in drones and unmanned aerial vehicles, brushless motors are the preferred choice due to their efficiency and light weight.
They culminate in construction robotics at not only the hobbyist level, but also at the industrial level – manipulators (industrial and laboratory robot arms), mobile and utility robots use them. Nothing prevents their use in the power tool sector. Among them can be mentioned home and garden screwdrivers, saws, grinders or lawnmowers.
