What is a DC Motor

In modern industry and life, although we cannot see motors, we deal with them every day, and DC motors are the most classic and common one. Whether it is your home electric fan, children's toys, car wipers, or even the power source behind an automated robotic arm, it may be driven by a DC motor.

 

So, what is a DC motor? Simply put, it is a device that converts DC electrical energy into mechanical energy. Although the history of DC motors can be traced back to the 19th century, it has not been eliminated by the times. Instead, it continues to be active in the fields of small drives and high-precision control. With the development of electronic control technology, the types of DC motors are constantly enriched, such as brushed DC motors, brushless DC motors, coreless DC motors, gear motors, etc. Different types are suitable for different scenarios and equipment.

 

In this article, we will take you through the principles, structures, and classifications to fully understand the working mechanism and application scenarios of DC motors, helping you quickly get started with this important electromechanical product.

 

 

How DC motors work: How do magnetic fields and currents produce rotation?

To understand the working principle of a DC motor, we can summarize it in one sentence: current flows through the wire, the wire is subjected to force in the magnetic field, thereby driving the rotor to rotate.

 

In other words, a DC motor is like an "energy conversion factory": it receives DC power from a power source, and then generates electromagnetic torque through the internal armature winding under the action of the magnetic field, thereby driving the mechanical part to rotate.

 

Working principle diagram

 

Why can it rotate? The principle actually comes from the "left-hand rule"

When current passes through a wire in a magnetic field, the wire will be subjected to a force perpendicular to the direction of the current and the magnetic field. This is the famous "Ampere force". You can use the "left-hand rule" to determine the direction of the force.

 

In a DC motor, this force acts on multiple coils on the armature, ultimately converging into a continuous rotational force.

 

Commutator: The key to continuous rotation

But there is a problem: if the coil always keeps one direction in the magnetic field, the motor will stop after half a turn. In order to solve this problem, a very critical device is added to the DC motor - the commutator.

 

The commutator will continuously switch the direction of the current during the rotation of the armature, so that the coil is always forced in the same direction in the magnetic field, thereby achieving continuous rotation.

 

This simple and efficient structure is one of the important reasons why DC motors are widely used. If you want to know more: Why do current and magnetic field generate torque? How does the commutator actually achieve commutation? How does the armature force process achieve continuous output? Then you can read this article "The Working Principle of DC Motors: The Wonderful Combination of Magnetic Field and Current"

 

 

What is a DC motor made of? Let me show you the key components

Although there are many types of DC motors (such as brushed, brushless, permanent magnet, etc.), their basic structures are roughly similar. Let's take a brushed DC motor as an example to understand its core components and functions one by one.

 

1. Armature: The main character of converting electrical energy into mechanical energy

The armature is the rotating part of the motor, usually composed of an iron core with copper wire wound around it. It is placed on the coil, and when direct current passes through the armature, it generates torque under the action of the magnetic field, thereby driving the motor to rotate.

 

The armature is both the "power output end" and the direct carrier of electromagnetic force. Its design affects the efficiency and performance of the motor.

 

2. Commutator: A "switch" that enables continuous rotation

The commutator is a device that connects the armature and the brushes, usually a segmented copper ring. Its function is to automatically switch the direction of the current when the armature rotates, thereby keeping the armature rotating continuously. It is an indispensable component in brushed motors.

 

3. Brush: Conductive bridge

The brush is a key component that introduces direct current from an external power source into the armature winding. Common materials are graphite or metal-graphite composites. It contacts and slides with the commutator, allowing the current to be stably delivered to the rotating armature.

 

It should be noted that brushes are wearing parts and will wear out after long-term use. They need to be replaced regularly, which is also an important part of brush motor maintenance.

 

4. Stator: The static part that generates the magnetic field

The stator is the stationary part of the motor, which is responsible for providing a constant magnetic field for the armature. The stator can be a permanent magnet (i.e. a permanent magnet DC motor) or a powered coil (i.e. an excitation DC motor). It can be divided into different types according to the different ways of generating the magnetic field.

 

5. Housing and bearings: structure and support

The motor casing mainly plays a protective and fixing role, while the internal bearing ensures the smooth and low-friction rotation of the armature, which is the basic structure to ensure the life and stability of the motor.

 

Summary: The core structure of a DC motor includes: armature, commutator, brushes, stator, bearings, etc. These components work together to complete the conversion of electrical energy into mechanical energy, which is the guarantee for the efficient operation of the motor.

 

 

When many people first get to know a DC motor, they may think it is just a small motor that can be turned by powering on. But in fact, DC motors can be classified from multiple dimensions, such as commutation method, magnetic field source, winding structure, etc. The following are the three most common classification methods:

 

According to the commutation method:

Brushed DC Motor

This is the most classic type of DC motor, with a simple structure and low cost. It switches the direction of the current through the mechanical contact between the brush and the commutator to maintain the continuous rotation of the motor.

 

Advantages: simple structure, easy to control, low cost, suitable for toys, small appliances, etc.

 

Disadvantages: brushes are easy to wear, short life, loud operation noise, frequent maintenance.

 

Brushless DC Motor

The brushless motor eliminates the brushes and commutator and uses an electronic control system for commutation, which makes it more efficient and has a longer life.

 

Advantages: high efficiency and quietness, long life, basically maintenance-free, suitable for mid-to-high-end equipment such as drones and power tools.

 

Disadvantages: Requires a dedicated controller, high cost, complex control system

 

According to the source of magnetic field:

Permanent Magnet DC Motor (PMDC Motor)

Permanent magnets are used to replace the field winding to generate the magnetic field. They have a compact structure and fast response. They are commonly used in electric vehicles, automatic doors, robots, etc. They can be either brushed or brushless motors.

 

Advantages: simple structure, small size, high efficiency, fast dynamic response

 

Disadvantages: The magnetic field strength cannot be adjusted, and the upper limit of power is limited by the magnetic material.

 

Excited DC Motor

The magnetic field is generated by the electromagnetic coil (excitation winding), which can be subdivided into series excitation, parallel excitation, compound excitation, etc. It is suitable for industrial equipment that requires large starting torque or a wide speed regulation range.

 

Advantages: adjustable magnetic field, strong torque, suitable for high power conditions

 

Disadvantages: complex structure, difficult to control, relatively large size

 

According to the winding structure or the number of power supply phases (mostly used for brushless motors):

The "phase number" of a motor refers to the number of channels through which current passes through the winding. Common types include single-phase, two-phase, and three-phase. This classification is particularly important in brushless DC motors (BLDCs), as different phase numbers have a significant impact on the motor's running stability, control methods, and application areas.

 

Single-phase brushless DC motor

Single-phase motors have the simplest structure and usually only require two wires to control. The drive circuit has a low cost, so they are often used in micro devices with low performance requirements.

Advantages: simplest structure, low cost, suitable for low torque applications such as small fans and portable devices

 

Disadvantages: large torque fluctuations, not as smooth as multi-phase motors when starting

 

Two-phase brushless DC motor

It is more complex than single-phase, usually using a four-wire or six-wire structure, and is more flexible in control. It is similar to the stepper motor structure, but the drive method is different.

Advantages: compact structure, stable operation, commonly used in micro devices and medical instruments

 

Disadvantages: Compared with three-phase motors, there is still a certain torque fluctuation

 

Three-phase brushless DC motor

It is the most mainstream and best-performing brushless motor structure on the market, with smooth operation and continuous torque, and is widely used in various mid-to-high-end applications.

Advantages: continuous torque, high efficiency, quiet operation, it is the most mainstream type of brushless motor, widely used in electric vehicles, power tools, drones, etc.

 

Disadvantages: The control system is complex and the cost is relatively high

 

Different classification methods reveal the key differences in motor structure, performance and application. It is worth noting that these classifications are not mutually exclusive. For example, a motor can be a three-phase brushless permanent magnet DC motor, which meets all three classification dimensions. Understanding these basics will help with subsequent selection and application decisions.

 

 

In modern engineering and life, DC motors are everywhere. With the advantages of simple control, fast response and diverse structures, DC motors are widely used in various products and systems. From household appliances to industrial automation, to drones and medical equipment, DC motors "empower" everything.

 

The following are several typical application scenarios, divided by industry or function:

1. Home appliances and daily electronic devices

DC motors are most common in small household appliances. They are compact and quiet, suitable for applications that require low voltage, low noise and low cost.

 

Vacuum cleaners, hair dryers, blenders (high speed, good stability)

 

Electric toothbrushes, electric shavers (using brushed or coreless motors)

 

Electric curtains, electric door locks (low voltage, low power consumption applications)

 

Common types: brushed motor, coreless motor, small brushless DC motor

 

2. Toys, models and entertainment electronics

From remote control cars to drones, DC motors play a key role. High speed, fast response, light weight and compactness are the basic requirements of such scenes.

 

Remote control cars and aircraft (using brushless motors to increase speed and endurance)

 

Robots, robotic arms (encoder DC motors that require precise control)

 

Common types: brushless DC motor, DC motor with encoder, coreless motor

 

3. Industrial automation and mechanical drive

The performance requirements for motors in industrial environments are higher, and they need to have characteristics such as high torque, strong controllability, and long life.

 

Automated production line (DC servo motor, encoder feedback system)

 

Conveying equipment, electric push rod (permanent magnet DC motor, gear motor combination)

 

CNC machine tools (high-precision brushless DC motors)

 

Common types: servo DC motor, high torque DC motor, motor with reduction gear

 

4. Transportation and green travel

Green travel tools such as electric bicycles, electric vehicles, and balance bikes basically use DC motors as their power core, especially high-efficiency brushless DC motors.

 

Electric bicycle (brushless hub motor)

 

Electric Scooter (24V / 36V Brushless Motor)

 

Smart balancing car (high torque DC motor with control system)

 

Common types: hub brushless motor, 48V brushless motor, high-efficiency DC motor

 

5. Medical devices and precision equipment

DC motors, especially coreless motors and servo motors, are also widely used in the medical equipment field, which has extremely high requirements on noise, volume and response speed.

 

Infusion pump, micro ventilator (coreless motor, sensitive response)

 

Electric surgical instruments (high speed, low noise brushless motor)

 

Ophthalmological examination equipment (Ultra-low vibration servo motor)

 

Common types: coreless DC motors, small servo DC motors, brushless motors

 

DC motors have been deeply embedded in our lives and industrial systems due to their flexible structure, simple control and quick response. From children's toys to high-precision medical equipment, from automated production lines to electric travel tools, all rely on DC motors to achieve drive and intelligence.

 

Different application scenarios have different requirements for the voltage level of DC motors. Want to know how to choose 12V, 24V, 36V or 48V according to your needs? You can refer to our "DC Motor Voltage Level Analysis Guide".