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What is a Brushless DC Motor? Explanation of the differences and types from brush DC motors

There are various types of motors, and the most suitable motor depends on the application.

One type of motor is a "DC motor," also called a "brush DC motor. The electrodes that conduct current inside the motor are called brushes, and while the brushes have some issues in terms of longevity and rotating power, they also have the advantage of low cost. Brushless DC motors are now available as a solution to improve the longevity and rotating power.

Brushless DC motors are used in a variety of fields, including electrical appliances, drive robots, personal mobility, and medical equipment. However, some people may be unfamiliar with brushless DC motors or may not understand the difference between brushless DC motors and brush DC motors.

This article provides an overview of brushless DC motors, their differences from brush DC motors, and their types.


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  1. 1.How Motors Work
  2. 2.How DC Motors Work
  3. 3.What are Brushless DC Motors?
  4. 4.Difference from Brush DC Motors
    1. 4.1.①Heat Dissipation
    2. 4.2.②Longevity
    3. 4.3.③High Power
    4. 4.4.④Energy Saving Performance
  5. 5.Types of Brushless DC Motors
    1. 5.1.Surface Magnet Type (Outer Rotor Type)
    2. 5.2.Embedded Magnet Type (Inner Rotor Type)
  6. 6.Types of Sensors for Brushless DC Motors
    1. 6.1.Encoder Specifications
    2. 6.2.Hall IC Specifications
    3. 6.3.Resolver Specifications
  7. 7.Summary


How Motors Work

Motor is a device that converts electrical energy into mechanical energy.

In a motor, a magnetic field is generated by a collection of magnetic fluxes flowing from the N to S poles of facing permanent magnets, and electromagnetic force is generated by passing a current through a coil (conductor) between them.


▼Principle of Electromagnetic Force Generation



How DC Motors Work

DC motor (hereafter referred to as brush DC motor) operates by applying DC power to the coil, which is the rotor.


▼Mechanism of Rotating


The commutator (*) attached to the end of the coil and the brushes contact with each other to control the current and rotation.


*A commutator is a component that changes the direction of the current flowing in the coil.


What are Brushless DC Motors?


Brushless DC motors do not have the commutator and brushes of brush DC motors, but instead use permanent magnets as the rotor. The commutator and brushes are not in contact with each other, but the electronic circuit is used to control the current while the motor rotates.

Brush DC motors have the advantage of being easy among of all motors to handle, but they also have the problem of being prone to wear due to the continuous contact of the brushes with the commutator.

Brushless DC motors can improve on this problem. Because they do not use brushes, they do not have the disadvantage of commutator wear, and their main feature is that they can be used for a long time.

For more information on the advantages and applications of brushless DC motors, please refer to this article.

Examples of Brushless DC Motor Advantages and Uses
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Difference from Brush DC Motors

Brushless DC motors and brush DC motors differ in other ways besides the presence or absence of commutator and brushes. Here are four differences between the two.


Item

Brush DC Motor

Brush DC Motor

Heat Dissipation

Low

High

Longevity

Relatively short
*Mabuchi Motor products achieve longevity without the need for replacement

Longer than brush DC motors

High Power

Difficult to achieve

Easy to achieve

Energy Saving Performance

Good

Superior to brushed DC motor 


①Heat Dissipation

Brushless DC motors have higher Heat Dissipation than brush DC motors, so their performance is less susceptible to degradation and relatively stable even after continuous operation.

Heat is generated when current passes through a motor. Brush DC motors have a layer of air between the coils and the motor case, which prevents the heat generated from dissipating outside. As the temperature inside the motor rises, it becomes difficult for current to flow through the coils, resulting in a gradual decrease in rotation speed.

On the other hand, in brushless DC motors, the coils and motor case are tightly sealed together, which prevents the formation of an air layer, allowing the heat generated by the coils to be efficiently dissipated.


②Longevity

The Longevity of a motor also differs depending on whether it has brushes or not.

With brushes, the commutator wears out due to rotation, whereas with brushless motors, there is no friction on the commutator, preventing damage to the components.

Therefore, brush DC motors are worn by the brushes and require periodic maintenance or motor replacement. Brushless DC motors, however, can continue to be used for a relatively long time due to the lack of friction.

In addition, in applications where Mabuchi Motor's brush DC motors are installed, Longevity is achieved without[HN1]  the need for maintenance or replacement. Like brushless DC motors, they can be used for a long period of time.  

③High Power

Compared to brush DC motors, brushless DC motors can carry a large current and thus show differences in rotational power.

If a high current is applied to a brush DC motor, the contact points between the commutator and the brushes may melt, resulting in failure. Therefore, it is difficult to achieve High Power.

Brushless DC motors do not have brushes, so there is no risk of contact melting. The advantage of brushless DC motors is that it is easy to achieve high power by applying a large current.


④Energy Saving Performance

Brushless DC motors offer better energy saving performance than brush DC motors. This is because brushless DC motors have higher rotational efficiency and consume less power.

Also, as mentioned above, brushless DC motors do not require frequent maintenance and replacement because the commutator and brushes do not wear out. They are also superior in energy saving performance in terms of reduced resource consumption.

However, unlike most products, Mabuchi Motor's brush DC motors are compact, high-power, and have excellent energy conversion efficiency.



Types of Brushless DC Motors

Brushless DC motors are divided into two types according to rotor structure.


Surface Magnet Type (Outer Rotor Type)

A type of motor with permanent magnets attached to the outer circumference of the rotor is called a "surface magnet type" or SPM (Surface Permanent Magnet) motor.

The surface magnet type operates only by rotation (magnet torque) caused by the electromagnetic force between the rotor and the coil. Compared to the embedded magnet type, the surface magnet type has issues such as low rotational efficiency and magnet peeling due to centrifugal force, but it has the advantage of being easily miniaturized.


Embedded Magnet Type (Inner Rotor Type)

The type with permanent magnets embedded inside the rotor is the "embedded magnet type," also called an IPM (Interior Permanent Magnet) motor.

In addition to the magnet torque, the embedded magnet type brushless DC motor also utilizes the reluctance torque generated by the magnetic resistance.


Types of Sensors for Brushless DC Motors

There are three types of sensors that control the rotation of brushless DC motors: encoder specifications, hall IC specifications, and resolver specifications.


Encoder Specifications

Encoder specifications use an optical encoder built into the motor to detect information such as the amount of rotation and angle of rotation.

When used in conjunction with a Hall IC, it can control motion with a high degree of accuracy. They are widely used in industrial robots such as factory assembly robots and unmanned transport machines.


Hall IC Specifications

Hall IC specifications are smaller than resolver specifications.

Hall ICs, also called Hall elements, play a role in detecting the rotational position of motors more accurately.

The IS series is applicable to Mabuchi Motor's products. They can be used in a wide range of applications from consumer to industrial equipment.

Resolver Specifications

Resolver specifications offer higher stopping accuracy and speed control with less rotation irregularity than the hall IC specification. It is also more resistant to external factors such as heat, oil, dust, and vibration. It is superior to the hall IC specifications in that it can be used in adverse environments.

The IR series is applicable to Mabuchi Motor's products. They are suitable for use in AGV and AMR used in warehouses and factories.

Mabuchi Motor also offers brushless DC motors that can be used in a wide range of applications. Please click here to see our product lineup.

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Summary

This article has described the following information on brushless DC motors

  • How Motors and DC Motors Work
  • Overview of Brushless DC Motors
  • Difference from Brush DC motors
  • Types of Brushless DC Motors(Rotor structure / Sensor)


Brushless DC motors are a new type of motor that overcomes the problem of longevity due to wear that has been a problem with conventional DC motors. They are expected to be used in a variety of fields and products because of their superior heat dissipation, high power, and energy savings as well as longevity.
 
Mabuchi Motor is focusing on the development of brushless DC motors, and has a product lineup that incorporates "elements required for each application“, such as waterproofing, high-speed rotation, and quietness, while based on "compactness, light weight, and high efficiency”.
 
We also have a worldwide sales network and can deliver your desired product in a short period of time. We also provide consistent support from product selection to post-purchase, including requests for samples and confirmation of usage. Please feel free to contact us if you have any questions, such as "I don't know which motor is best for my product" or "I am looking for a reasonable motor.

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