Today, electric motors are everywhere, providing motion for a variety of equipment, both domestic and industrial.
When selecting an electric motor (sometimes referred to as an “electric machine”), the challenge lies in choosing one that is suitable for the task at hand, as there are numerous options available.
Here is a guide to the different types of electric motors and their functions, created by our team of electric motor experts. This document will help you identify which type best meets your specific needs.
What is an Electric Motor?
An electric motor is a device designed to convert electrical energy into mechanical motion. It operates based on the fundamental principle of interaction between magnetic fields generated by electrical currents and external magnetic fields.
When an electric current flows through the coils of an electric motor, it creates a magnetic field that interacts with an external magnetic field, typically produced by permanent magnets. This interaction generates either rotational or linear movement, depending on the motor’s design.
Electric motors are widely used in various aspects of daily life, including:
- Household appliances
- Electric vehicles
- Industrial machinery
- Pumps
- Fans
- Air conditioning systems
- Power tools
- And many other applications
Their high energy efficiency and low environmental impact make them essential components in the transition to cleaner and more sustainable energy sources.
The Two Main Categories of Electric Motors: DC and AC
DC Electric Motors (Direct Current)
A direct current (DC) motor operates by utilizing a continuous flow of electricity that moves in a single direction.
This type of motor uses a magnetic field generated by permanent magnets or coils positioned in the stator, while a continuous current flows through the rotor’s coils. The rotary motion is generated by the interaction between the magnetic field and the direct current in the rotor.
AC Electric Motors (Alternating Current)
Alternating current (AC) motors convert alternating current into mechanical motion through a process called electromagnetic induction.
These motors typically consist of two main components: an external stator with coils powered by AC to generate a rotating magnetic field, and an internal rotor attached to the shaft that creates a second rotating magnetic field.
AC motors are not as easily controlled in speed as DC motors. To better control their frequency (and thus their speed), they are typically used with frequency converters.
DC vs. AC Motors: In Brief
In summary, the key difference between AC and DC motors lies in the type of electrical current they use to operate.
AC motors work on alternating current and rely on a rotating magnetic field to induce motion. Meanwhile, DC motors operate using direct current and exploit a fixed or rotating magnetic field to generate rotation.
Additionally, it’s worth noting that DC motors are the logical choice for most applications requiring high torque at low speeds.
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Types of DC Electric Motors
Brushed DC Motors
The brushed DC motor, also known as a brush DC motor, gets its name from the “brushes” that are essential components of this motor type.
These brushes are movable electrical contacts that maintain direct contact with the rotating parts of the rotor. Typically made from graphite or carbon, the brushes are mounted on a component called a “commutator.” The brushes provide the electrical connection between the external power source (the DC supply) and the rotor’s rotating coils.
How Brushed DC Motors Work
As the rotor turns, the brushes maintain electrical contact with the commutator segments, reversing the direction of the current in the rotor coils with each half-turn. This reversal of current causes the direction of the magnetic field in the rotor coils to change, keeping the rotation continuous.
Advantages and Disadvantages of Brushed DC Motors
The main advantage of brushed DC motors is their simplicity and relatively easy speed and torque regulation by adjusting the supply voltage.
However, these motors come with disadvantages such as brush wear over time, requiring periodic maintenance, and electromagnetic disturbances generated by the moving brushes.
Brushless Motors
Unlike traditional brushed electric motors, brushless motors do not have brushes or mechanical commutators to reverse the direction of the current in the motor’s armature (the rotating part). Instead, they rely on an electronic controller to manage the commutation of the motor’s coils.
How Brushless Motors Work
Brushless motors use permanent magnets inside the rotor (rotating part) and coils in the stator (the stationary part) of the motor. The electronic controller sends signals to switch the coils in sync with the rotor’s rotation, creating a rotating magnetic field that turns the rotor. This design eliminates the friction associated with brushes, leading to reduced wear and greater energy efficiency.
Advantages of Brushless Motors
Advantages of brushless motors include higher efficiency, longer lifespan, reduced maintenance, and quieter operation compared to brushed motors. They are also more compact and lightweight, making them ideal for applications where space is limited.
Furthermore, due to their advanced electronic control, brushless motors allow for better speed, torque, and direction management, making them perfect for applications requiring precise regulation.
You’ll often find brushless motors in equipment such as:
- Drones
- Electric vehicles
- Power tools
- Fans
Types of AC Electric Motors
Universal Motors
Universal motors, also known as AC/DC motors, can operate on both alternating current (AC) and direct current (DC).
These motors have a stator winding (the stationary part) and a rotor winding (the rotating part). The stator winding is powered by AC, while the rotor winding is powered by DC. This design allows universal motors to work efficiently on both types of current.
Advantages and Disadvantages of Universal Motors
Universal motors offer several advantages, including their ability to run on different power sources, their compactness, and their simple design.
However, they tend to be less efficient and produce more heat compared to specialized motors designed to operate on either AC or DC.
Synchronous Motors
A synchronous motor is a type of electric motor that runs at a constant speed synchronized with the frequency of the supplied electrical power. This means the speed of the motor is directly linked to the frequency of the power supply and the number of pole pairs in the motor.
How Synchronous Motors Work
The operation of a synchronous motor relies on the synchronization between the rotating magnetic field produced by the stator windings (the fixed part of the motor) and the magnetic field produced by the permanent magnets or windings in the rotor (the moving part of the motor). When these magnetic fields are in phase, the rotor remains synchronized with the stator’s rotating magnetic field, maintaining a constant speed.
Use of Synchronous Motors
Synchronous electric motors are used in applications where precise, constant speed is required, such as in clocks, synchronization equipment, power distribution systems, and constant-speed machine tools.
Why Synchronous Motors Can Be Expensive
Synchronous motors often require more complex control systems to maintain synchronization, making them more costly to implement compared to other types of motors, such as asynchronous (induction) motors.
Induction or Asynchronous Motors
The induction motor (also known as an asynchronous motor) is one of the most widely used types of electric motors in industrial, commercial, and residential applications. It works on the principle of electromagnetic induction, discovered by Michael Faraday in the 19th century.
How Induction Motors Work
- Stator winding: The stator is the fixed part of the motor, made up of coils of electrical wire wound around laminated iron cores. When alternating current (AC) is applied to these coils, it generates a rotating magnetic field in the stator.
- Rotor: Inside the stator is the rotor, which is the moving part of the motor. The rotor is typically made of aluminum or copper conductors but is not powered by an external current. Instead, it is placed within the rotating magnetic field generated by the stator.
- Electromagnetic induction: The rotating magnetic field in the stator induces currents in the rotor due to Faraday’s law of electromagnetic induction. These induced currents create their own magnetic field, which interacts with the stator’s field.
- Rotor rotation: The magnetic forces result in the rotation of the rotor, which drives the mechanical work (e.g., turning the wheels of a machine or equipment).
Advantages of Induction Motors (Asynchronous Motors)
Induction motors are valued for their simple construction, reliability, low cost, and the absence of brushes, reducing maintenance requirements.
These motors are also very efficient and offer good energy performance.
Use of Induction (Asynchronous) Motors
All the advantages mentioned in the previous section make induction motors the most widely used in the industry.
They are found in many machines and applications, such as:
- Pumps
- Fans
- Compressors
- Air conditioning systems
- Washing machines
- Machine tools
- Blowers
- Lifting equipment
Types of Induction or Asynchronous Motors
Three-Phase Motor
The three-phase motor is the most common and widely sold induction motor due to its high reliability and ability to generate continuous high power.
It is named as such because it receives electricity in the form of three sinusoidal alternating voltages, each phase shifted by 120 degrees from the others.
The speed and torque of three-phase motors can be controlled by adjusting the frequency or voltage of the phases.
Single-Phase Motor
This type of motor operates on a single-phase electrical supply. It is suitable for domestic and light applications requiring less power.
ATEX Motors
“ATEX” stands for “Explosive Atmosphere.” ATEX motors are designed for environments where there is a risk of fire or explosion.
Smoke Extraction Motor
This type of motor is primarily used in fans that evacuate smoke and hazardous gases in the event of a fire. It is built to withstand extreme temperatures and exposure to gases.
Two-Speed (Dual-Polarity) Motor
Also known as a “polarity-reversing motor” or “dual-direction motor,” this type of motor features a specially designed rotor.
The rotor typically consists of two separate windings, each connected to an opposite polarity.
To change the motor’s rotation direction, simply reverse the polarity of the electrical supply applied to the rotor windings.
Slip Ring Motor
Slip ring motors are often used when specific performance characteristics are required, such as smooth startups, precise speed control, or adjustable rotor voltage.
They are more complex and require regular maintenance due to the wear of brushes and slip rings that transfer electrical current to the rotor.
Brake Motor
Brake motors combine the functions of a motor and a brake. Their main characteristic is that they can drive a mechanical load (such as a conveyor, winch, or lifting equipment) and, when deactivated, function as a brake to stop the rotation of the load in a controlled manner.
This type of motor is commonly used in applications where it is necessary to hold a load in a specific position or slow it down quickly while recovering electrical energy.
Reduced Height Axis Motor
A reduced height axis motor is a specially designed electric motor in which the shaft height (the distance between the motor base and the rotation axis of its output shaft) is minimized.
This design is often sought after in applications where the available space for motor installation is limited in height.
Special-Purpose Electric Motors
Special-purpose electric motors, also known as custom or specialized electric motors, are designed and manufactured to meet unique and specific application requirements.
Unlike standard electric motors, which are mass-produced with standardized sizes and specifications, special-purpose motors are tailored for applications where performance, size, power, voltage, speed, or environmental conditions are outside the norm.
Here are some examples:
Stepper Motors
A stepper motor is a type of electric motor primarily used in applications requiring precise positioning (such as 3D printers, scanners, and CNC machines).
Unlike conventional electric motors, stepper motors do not rotate continuously. Instead, they move in discrete steps—hence the name.
Key Characteristics of Stepper Motors:
Precision Positioning: The rotor of a stepper motor advances by a fixed angle with each electrical pulse it receives. This angle is called a “step.” Some stepper motors can also perform half-steps, providing even finer position control.
Ease of Control: They are relatively easy to control using dedicated electronics, making them suitable for various applications. Stepper motor controllers allow users to define the number of steps and the direction of rotation.
Linear Motors
A linear motor converts electrical energy into linear motion, meaning movement along a straight line.
Unlike conventional rotary motors, which produce rotational motion, linear motors generate linear displacement directly.
They are used in various applications where precise and rapid linear motion is required.
Advantages of Linear Motors
Linear motors offer high precision, no mechanical contact (reducing wear), energy efficiency, and rapid response to commands.
Hysteresis Motors
Hysteresis motors utilize magnetic hysteresis—a phenomenon in which a magnetic material retains some magnetization even after the inducing magnetic field has changed—to generate rotational movement.
Applications of Hysteresis Motors
Hysteresis motors have been widely used in applications requiring quiet operation, low speed, and high reliability, such as electric clocks, turntables, medical devices, and measuring instruments.
Omnifab: Your Trusted Partner for Electric Motor Sales and Repairs
In conclusion, electric motors come in many forms, operating based on different electromagnetic principles.
To achieve optimal performance in applications requiring movement generation, it is crucial to select the right motor designed for your specific needs—and even to understand certain calculations to determine a motor’s efficiency.
To make the best choice when purchasing an electric motor, rely on a team with proven expertise in the field and the know-how to repair electric motors.
At Omnifab, we don’t just sell motors—we also provide maintenance and repair services for electric motors, ensuring you complete peace of mind.
Have questions? Contact us today!