All aspects of living are controlled generally by technologically driven electric motors. A few may argue the fact in ignorance until you see the reality when your coffee maker break down or your steam fan stops working and then your technician tells you the humble motor is the culprit.

In this post, DHmotor will give a comprehensive overview of brushed DC motor and brushless DC motor.

Difference Between Brushed and Brushless Dc Motor？

The primary difference between brushed and brushless motors is that brushed motors are mechanically driven and brushless are electronically driven.

In brushed motors, the stator (stationary part) contains permanent magnets while the rotor (moving part) contains electromagnets. Carbon brushes in physical contact with the commutator in the rotor transfer the electric voltage to it.

This voltage creates an electromagnetic field in the rotor. By continually flipping the polarity of the magnetic pull via the commutator, spinning motion is achieved.In the diagram below, the armature, commutator, brushes, and field magnet configuration can be seen.

In brushless motors, flipping takes place. The rotor contains the permanent magnets and the stator creates the electromagnetic field. Instead of brushes, an electronic controller creates a three-phase variable current that powers the motor’s coils in succession.

This forms a rotating magnetic field in the stator that powers the rotor’s magnets and creates the spinning motion.As the diagram below shows, the electric coils in the brushless motor are energized in a specific sequence which causes the permanent magnets on the rotor to rotate or flip.

Furthermore, Electronic Controller Unit (ECU), will determine the position of the rotor and which coils to energized. This is done without any physical contact and allows for a more efficient, longer-lasting DC motor.

1. What Is a Brushed Dc Motor?

A brushed DC motor is an electric motor, commutated internally, that is operated from a direct current power supply. It uses an electric brush to deliver current to the motor windings by mechanical commutation.

2. What Is a Brushless DC Motor?

A Brushless DC Motor (BLDC) is an electric motor powered by a direct current voltage supply and commutated electronically instead of by brushes like in conventional DC motors. BLDC motors are more popular than the conventional DC motors nowadays.

If you want to learn more about brushless DC motors, you can check out our article here: Brushless DC motor: what it is and how does it works?

3. Brushed Vs Brushless Dc Motor -Pros and Cons

Pros of Brushless DC motor

Brushless DC motors offer several benefits such as higher efficiency, longer lifespan, and reduced maintenance. However, brushless motor tools are typically more expensive and require more advanced electronic controllers compared to brushed motor tools.

Whether brushless motor tools are preferred choice depends on your specific needs and preferences. Meanwhile the following factors will help to determine if brushless motor tools are a good fit for you:

Power requirements: Brushless motors are more efficient, which means they can deliver more power with less heat. This makes them ideal for demanding applications such as heavy-duty construction work.

Applications: Brushless motor tools are ideal for high-volume, high-powered applications where long run times, efficiency, and durability are important. They may not be the best choice for low-power, infrequent use.

Cost: Brushless motor tools are typically more expensive than brushed motor tools. However, the longer lifespan and reduced maintenance costs can make up for the initial investment over time.

Ease of use: Brushless motor tools typically have more advanced electronic controllers and require more knowledge and experience to operate. Consider your level of expertise and experience before purchasing a brushless motor tool.

Battery life: Brushless motor tools are often designed for use with rechargeable batteries, which can be a convenience for some users but may limit the overall run time for others.

Cons of Of Brushless DC Motor

High cost: Brushless DC motors are typically more expensive than brushed DC motors due to the complex electronic controls required for operation.

Complex maintenance: Brushless motors require specialized knowledge and equipment for repair and maintenance, making them less accessible to the average user.

Higher power requirements for controller: Brushless motors require an electronic controller that consumes additional power, reducing overall efficiency.

Electromagnetic compatibility issues: Brushless motors can generate electromagnetic interference, which may impact other electronic devices in close proximity.

Limited speed range: Brushless motors may have a limited speed range compared to brushed motors, making them less suitable for some applications.

Requires cooling: Brushless motors may require cooling to prevent overheating during high-power operation, adding complexity and cost to the overall system.

Sensitive to voltage fluctuations: Brushless motors are more sensitive to voltage fluctuations compared to brushed motors, which may impact performance and lifespan.

4.Brushed Vs Brushless Motor price

As we have seen from their pros and con above, which helps to determine their weak point and strength, generally speaking these have a strong effect on their prices as brushless DC tends to be more expensive to acquire than brushed DC.

Price of Brushless DC motor

24V Brushless DC motor is sold at $35

Price of Brushless DC motor

24V Brushed DC motor is sold at $18

5. Efficiency of Brushless Dc Motor Vs Brushed Dc Motors

As mentioned earlier above, brushless DC motors are more efficient than their brushed counterpart. This again, is because the lack of brushes means that no brushes will be constantly in contact with the commutator (like they are in brushed motors).

This lack of contact means there’s also a lack of friction and heat created in brushless motors. Less energy lost in the form of heat, makes a brushless motor more efficient. In fact, brushless DC (BLDC) motors typically have an efficiency of 85%-90%, while brushed motors are usually only 75%-80%.

This means that for applications like power tools, for example, this improved efficiency extends battery life (meaning more can be done between charges).

How to Calculate the Efficiency of Dc Motors

To fully characterize a motor and determine its efficiency, you need to measure the following parameters:

• Voltage (V)
• Current (A)
• Throttle input (%)
• Motor load or torque (Nm)
• Speed (RPM)

The factors listed above are important because they allow you to determine the following key performance indicators:

• Mechanical power (Watts) = Torque (Nm) * Speed (rad/s)
• Electrical power (Watts) = Voltage (V) * Current (A)
• Motor Efficiency = Mechanical power / Electrical power

6. Diagram of Brushless Vs Brushed DC Motor

• Disassemled Brushless DC motor

• Disassembled Brushed DC motor

7. Brushed Vs Brushless DC Motor Principle

Principle of Brushed DC Motor

Now let’s dig further into their operating mechanism by looking at the principle on which work. Brushed DC motors operate based on advanced electromagnetic principles.

The interaction between the stator’s magnetic field and the armature windings results in torque generation. Mathematical models, including equations and algorithms, are used to optimize and control motor performance, ensuring efficiency and precision in various applications.

How They Work

A brushed DC motor has two important parts, such as stator and rotor. Stator is the stationary portion of the motor and the rotor is the rotating portion of the motor.

The rotor usually highlights coils around an iron core and enclosed by magnets located in the stator.

In a brushed motor, commutators are located around the shaft and connected with each other at every 120°. Commutators do not make mutual contact with each other.

Commutators revolve together with the spin of the shaft. Every commutator is joined to a part of one coil and another part of another coil.

In it, two brushes are stable at 0° and 180° positions so that those can make connection with the commutators. The brushes are joined to a DC power supply and current flows through the direction like brush to commutator, then commutator to coil and then coil to brush.

The exterior view of a brushed motor is displayed below：

Types and Variations of Brushed DC Motor

Permanent Magnet Types: Permanent magnet brush DC motor is the most favorite among all brushed DC motors. This applies stable magnet to generate the magnetic field in the stator.

This magnetic field is needed to operate the motor. The response to the change of input voltage of this motor is quite good. The speed of motor is easily controllable.

Shunt-wound Types: The shunt-wound brushed DC motor is made with the parallel connection between field coil and the rotor. Thus, stable torque at less speed can be easily generated by using this motor. This kind of motor is perfect in industrial and automotive uses with rigid speed control conditions.

Series-wound Types: The shunt-wound brush DC motor is made with the series connection between field coil and the rotor. The electric current in the stator and rotor is gained under load condition which makes them perfect for high-torque uses such as cranes and winches.

The speed of the brushed motor can be calculated through the following equation:

• N = The speed of the brushed motor
• E = The value of EMF
• A = Number of parallel path
• P = Number of poles
• j = Magnetic flux (Wb) Z = Total number of conductors in the armature.

Principle of Brushless DC 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. In case 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 field 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.

Consider the figure below in which 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 forces (when North-North or South-South alignment). By this way motor moves in a clockwise direction.

How Do We Know Which Stator Coil Should Be Energized and When to Do So?

As shown in the above diagram, one might ask: that how we know which stator coil should be energized and when to do. This is because; the motor continuous rotation depends on the switching sequence around the coils. Hall sensors give shaft position feedback to the electronic controller unit.

Based on this signal from sensor, the controller decides particular coils to energize. Hall-effect sensors generate Low and High level signals whenever rotor poles pass near to it. These signals determine the position of the shaft.

How Do I Know if My Motor Is Brushed or Brushless?

There are a few ways to tell a brushed DC motor from a brushless DC motor without opening the motor. One way is to look at the physical characteristics of the motor.

A brushed DC motor will typically have exposed commutator plates and brush holders on the outside of the motor, whereas a brushless DC motor will not.

Another way to tell the difference is by listening to the motor. A brushed DC motor will make a characteristic “brushing” sound as the brushes make contact with the commutator plates, whereas a brushless DC motor will be much quieter.

A brushless DC motor generally has three windings, in delta configuration, and thus will have three leads. (It may additionally have a five- or six-wire connector for a Hall sensor). Whereas a brushed DC motor has two wires.

However, if you can’t count the wires, just apply some DC voltage to the motor. If it runs without being connected to a controller, it’s a brushed motor. If not, it’s a brushless motor.

Finally, you can also check the power supply of the motor. A brushed DC motor typically requires a direct current power source, whereas a brushless DC motor requires an alternating current power source.

It’s important to note that some brushless DC motors have an outer casing that covers the internal components and make it difficult to identify the motor type through its power source unless it is opened.

Application of Brushed DC motor

Brushed DC motors have variety of application usage such as in:

• Paper machines
• Cranes
• Sewing machines
• Power tools
• Rolling mills
• Kid’s toys
• Robots
• RC cars
• Electric toothbrush

Is It Worth Buying Brushed Vs Brushless?

No, although brushed DC motors are relatively cheaper to acquire looking at the initial cost, however, ongoing cost that will be incurred as a result of brush damages and periodic replacement is worth the extra cost presented by brushless DC motor, even though the later is quite expensive with reduced cost of maintenance.

Are Brushed Motors Louder Than Brushless?

Yes, that is due to electrical noise caused by the sparks generated in the electrical contact between brush and commutator. This is why brushed DC motors are unsuitable for application that requires silence operation.

Conclusion

Advantages of brushless motors, such as increased efficiency, longer lifespan, and reduced maintenance, can result in reduced operating costs and increased reliability over the long term.

These benefits may make the higher upfront cost worth it for applications where performance and reliability are critical.However, for applications where cost is a major concern and performance requirements are lower, a brushed DC motor may be a more cost-effective solution.

Ultimately, the decision to use a brushless DC motor should be based on a comprehensive analysis of the specific requirements, including performance, reliability, maintenance, and cost.

Related readiing: How to install brushed DC motors