When considering the optimal motor for your project, the choice between a brushed DC motor and a brushless DC motor (BLDC) can have significant implications for performance, cost, and longevity. Both motor types have their specific advantages and disadvantages, and understanding their key differences is crucial for selecting the most appropriate option.
This article delves into the main distinctions between brushed and brushless DC motors, focusing on design, efficiency, maintenance, cost, and application areas, and provides data-supported comparisons.
Brushed DC Motors
Ampere’s law and the law of electromagnetic induction form the foundation of the brushed DC motor’s operation. The motor contains components such as stator, rotor, brushes and commutator. When the DC power supply supplies power to the motor through the brushes, the stator generates a stationary magnetic field, while the rotor is connected to the power supply through the brushes and commutator to form a rotating magnetic field.
The motor rotates as a result of the electromagnetic torque produced by the interaction between this rotating magnetic field and the stator magnetic field. During the operation of the motor, the brushes slide on the commutator to achieve current commutation and keep the motor rotating continuously.
Key Characteristics:
- Brushes: Brushed motors contain physical brushes that make contact with the commutator, creating electrical pathways.
- Commutator: It is a mechanical switch that flips the motor windings’ current direction.
- Winding Placement: Windings are located on the rotor.
- Magnet Placement: Permanent magnets are placed around the stator.
Pros | Cons |
|
|
Brushless DC Motors (BLDC)
A synchronous motor that functions differently from a brushed DC motor is called a BLDC motor. The rotor of a brushless DC motor has permanent magnets, whereas the stator contains windings. The controller generates a rotating magnetic field by applying a specific current waveform to the stator windings. The motor rotates as a result of electromagnetic torque produced by the interaction between this revolving magnetic field and the magnetic field produced by the rotor’s permanent magnets.
During the operation of the motor, the controller detects the position information of the rotor and adjusts the current waveform in the stator windings to achieve precise control of the motor.
Key Characteristics:
- Electronic Commutation: Instead of using mechanical brushes to change the current, BLDC motors employ electronic controllers.
- PM on the Rotor: Permanent magnets make up the rotor, while the stator’s windings do the same.
- Sensors for Feedback: Sensors such as Hall-effect sensors are used to determine the rotor’s position and to control commutation.
Pros | Cons |
|
|
Key Differences Between Brushed and Brushless DC Motors
Design
The design and construction are where the biggest differences can be found. Brushes and a commutator are used in the mechanical commutation process of brushed motors. In contrast, BLDC motors save mechanical wear and do away with the need for brushes by commuting via an electronic control circuit.
Feature | Brushed DC Motor | Brushless DC Motor (BLDC) |
Commutation | Mechanical (Brushes and Commutator) | Electronic (Controlled by Circuit) |
Rotor | Wound Copper Wire | Permanent Magnets |
Stator | Permanent Magnets | Copper Windings |
Control | Simple electrical control | Requires electronic control unit |
Efficiency and Performance
The efficiency of BLDC motors is often higher than that of their brushed equivalents. By eliminating frictional losses and improving heat dissipation, the removal of brushes raises overall efficiency. Brushed motors usually run at 75–80% efficiency, whereas BLDC motors can reach 85–90%.
In terms of performance, BLDC motors can achieve higher speeds, better torque per weight, and more precise control due to electronic commutation. Additionally, the ability to sense rotor position enables smooth and accurate speed and torque control in BLDC motors.
Feature | Brushed DC Motor | Brushless DC Motor (BLDC) |
Efficiency | 75-80% | 85-90% |
Max Speed (RPM) | 5,000 – 10,000 | 10,000 – 100,000 |
Torque-to-Weight Ratio | Moderate | High |
Heat Dissipation | Limited due to internal heat generation | Good due to external windings |
Maintenance and Lifespan
The physical brushes and commutators in brushed motors are prone to wear over time, leading to shorter lifespan and more frequent maintenance requirements. Regular replacement of brushes is necessary to ensure optimal performance.
In contrast, BLDC motors do not suffer from mechanical wear as they do not have brushes. This makes them much more reliable over time and suitable for applications where longevity and reduced maintenance are crucial. BLDC motors can often last significantly longer than brushed motors, sometimes up to 10,000-20,000 hours of continuous operation.
Feature | Brushed DC Motor | Brushless DC Motor (BLDC) |
Maintenance | High (Brushes need to be replaced regularly) | Low (No brushes, fewer wear points) |
Lifespan (hours) | 1,000 – 3,000 | 10,000 – 20,000 |
Noise
Noise
brushed DC motors produce noise because of the mechanical interaction between the brushes and the commutator. As the motor operates, the brushes continuously rub against the commutator, leading to audible noise. The amount of noise increases with motor speed and wear of the brushes.
Key Sources of Noise:
- Brush-to-commutator friction
- Arcing at the brushes
- Vibration due to mechanical parts
In contrast, the primary sources of noise in BLDC motors are usually related to bearing friction and rotor vibration, but these are generally much quieter than the noise generated by brushed motors.
Key Sources of Noise:
- Bearing friction
- Rotor imbalance (if not properly maintained)
- Minor vibration due to electromagnetic forces
Motor Type | Speed (RPM) | Noise Level (dB) |
Brushed DC Motor | 1000 | 55 |
3000 | 60 | |
5000 | 65 | |
Brushless DC Motor | 1000 | 40 |
3000 | 42 | |
5000 | 45 |
Cost
Brushed DC motors are cheaper upfront due to their simpler design and control mechanisms. However, their long-term costs may rise due to the need for regular maintenance and parts replacement. BLDC motors, while more expensive to manufacture and require an electronic controller, tend to have lower maintenance costs over time.
Feature | Brushed DC Motor | Brushless DC Motor (BLDC) |
Initial Cost | $10 – $50 | $50 – $150 |
Long-term Cost | Higher (Maintenance adds to cost over time) | Lower (Minimal maintenance required) |
Applications
Applications where great performance is not required and cost is a crucial consideration frequently utilize brushed motors. These include toys, small appliances, and basic industrial machinery.
BLDC motors, on the other hand, are often used in high-performance applications such as robotics, electric vehicles, drones, and advanced industrial machinery due to their superior efficiency, precision, and lifespan.
Feature | Brushed DC Motor | Brushless DC Motor (BLDC) |
Common Applications | Toys, basic machinery, simple consumer products | Drones, electric vehicles, robotics |
Conclusion
When choosing between these two motor types, it’s essential to consider the application’s requirements—such as desired speed, precision, and maintenance tolerances.
For high-efficiency and long-lasting performance, BLDC motors are typically the better choice. However, for low-cost applications where simplicity and affordability are key priorities, brushed DC motors may offer a more suitable solution.