DC electric motors are essential components in various equipment used in industrial applications. They mostly come in two variations: DC Brushed Motors and DC Brushless Motors (BLDC). Depending on their application, different businesses opt for one of these motors. Learning the difference between them helps businesses and technicians to find and choose the best one.
Importance of Understanding the Key Difference between Brushed and BLDC Motors
Just like you cannot use an AC motor where control over rpm and torque is required, you cannot use a Brushed DC motor where a Brushless DC motor can give more efficient output. Both motors, though operate on DC, but have various key differences that make them fit for different applications.
Both of these motors have their pros and cons. Depending on their advantages and disadvantages, you can choose the right for after analysing where you are going to use it. It is the application requirement that will help you decide, whether a Brushed DC or BLDC motor will be suitable.
The key difference from where the names of both are assigned is based on commutators. Brushed DC motors have carbon brushes usually, which are used as commutators. In BLDC motors, the commutators are electronic instead of mechanical as used in brushed motors.
In this article, you will learn the key differences between both of these motors. This learning will help you to choose the best one among these two to make your work more controlled, smooth and efficient.
Brushed DC Motors
All the mechanical machines are constructed by a combination of different mechanical pieces. So is the case with brushed and BLDC Motors. When the construction of brushed motors is under consideration, you can these motors use coil-winding of wires around the iron core to create a magnetic field. These coils rotate freely and it drives the motor shaft. This whole set is called “rotor”. You may find some coreless DC Brushed motors as well. When the core is absent, the winding is self-supporting as the core is used to support the windings.
The rotor is a rotating component while the fixed part is names as stator. The state holds the permanent magnets inside it. This keeps a permanent static magnetic field intact and holds the rotor inside it.
The third main component is the commutator. The torque is created by the rotation of spin. To create a magnetic field in the rotor, a current is needed. The commutator is fixed between brushes, that are fixed around it on the stator. The commutator works as a switch and keeps switching different windings to turn on and off which keeps the rotor rotated constantly.
The rotation of the brushed motor is when the DC current is applied it creates a magnetic field in the rotor that repels the fixed magnetic field of the stator, and it causes rotation of the shaft. Furthermore, the use of an H-bridge helps in controlling the speed, torque, voltage applied and most importantly the direction of rotation.
Brushless DC Motors
Although the functioning of brushless DC motors is the same as the brushed DC motors, that is the principle of repulsion and attraction of magnetic field between rotor and stator. But their construction is different. This makes BLDC different from brushed motors.
The construction of the rotor and stator is opposite to rushed motors. The rotor in BLDC has a permanent magnet and the stator has winding coils opposite to brushed motors. So, the commutator here in the BLDC is electrical instead of mechanical as in brushed motors.
Another difference in construction is no. of phases. The phases are actually the winding units of stators. The number of winding units is equal to the number of phases that a BLDC motor has. Although there is no restriction on the number of phases usually 3 phases are used in the development of BLDC motors. These 3 phases are either aligned as Delta or Wye configuration.
Moreover, another difference is the number of magnetic poles present on the rotor’s magnet in a BLDC motor. There are usually two poles at minimum as south and north poles on the rotor. There can be more if required. The need and function will be discussed in the application section of both motors.
Another very important difference is the deployment of complex electronics in BLDC motors as compared to brushed motors such as Hall-sensor and 3 H-gates for each phase.
Key differences between Brushed and BLDC Motors
Till now you have learned why it is important to know the difference between both motors and also the basics of construction principles of both brushed and BLDC motors. You will now learn the key differences based on the advantages and disadvantages of both types.
Difference in Speed and acceleration
Due to more weight in brushed motors, the speed and acceleration are lower. Further lowering of speed is because of the presence of brushes and mechanical commutator. This makes the brushed motors fall in the category of medium-speed motors. The commutator is attached through brushed mechanically.
When the high speed is in intent, the contact between brushes and commutator will behave erratically hence lowering speed. Another reason for the lesser speed is the use of a laminated iron core at the centre and due to large inertia, the speeds are low.
On the other hand, BLDC motors lack mechanical commutators, hence there is theoretically no resistance present as compared to their counterpart. This gives an edge to BLDC motors for very high speeds and functional accuracy. So, the speeds are higher in BLDC as compared to brushed motors, but with a higher cost.
Electrical and Acoustic Noise
Due to the presence of mechanical brushes and commutators, brushed motors produce more electrical noise than BLDC motors. Although the use of a capacitor may reduce the noise it cannot be eliminated 100%. On the other hand, no such components are present in BLDC motors, which makes them very silent to be used on noise-sensitive applications.
Maintenance
As for now, you have learned a lot about brushes and commutators. Both are mechanical components and are in continuous friction against each other. This causes continuous wear and tear in both brushes and commutator which needs frequent replacements. Hence the maintenance cost is high and needed on and off.
On the other hand, BLDC motors lack any such component which make them a type of maintenance-free motors.
Torque Ripple
It is a mechanical phenomenon that is named for mechanical vibrations in motors. Due to more mechanical components in brushed motors, torque ripple is higher hence the vibrations are more frequent at high speed in Brushed DC motors as compared to BLDC.
Lifetime
The life cycle of BLDC is higher than the brushed motors due to the construction design presence of less mechanical components. Due to large mechanical wear and tear, there comes a time for brushed motors from where they no longer remain operational.
Cost
Finally, the associated cost of a brushed motor is far less than a BLDC motor. It is because of its simple construction and mature design. Although some components are absent in BLDC due to the presence of complex electronics, these are costlier than brushed motors.
Factors to Consider Before Selecting a DC Motor
So, as far now, you have a complete understanding of both types of brushed and brushless DC motors. To learn which one will suit best for your application. You will need to assess the requirements.
If you want a DC motor for simple applications then brushed motors suitable. These motors are cheap and easily available. Depending on the control, speed, the required amount of torque and cost, you can choose the brushed motor. Keep in mind that the life of these motors is less than BLDC motors.
On the other hand. BLDC motors are preferred when you need high performance and high speed with more control over the functionality. Moreover, when you want to use a DC motor in a noise-sensitive application, you will need a BLDC. The life of BLDC is far higher than Brushed motors and your investment will serve you for a longer time.
Summary
Although the selection of motors depends on various factors and as you have learned all the key differences. The room for the usage of brushed motors still exists even when the availability and associated costs of BLDC motors have declined. You need to consider all the factors for both brushed and BLDC motors before choosing any of them for your application.
