Electric motors are used in a wide variety of applications, from small toys to large industrial machines. As you navigate the world of electric motors, you’ll find that each type has its own distinctive benefits and drawbacks. In this article, let’s explore several of the most widespread electric motors and gain an understanding of their respective operations.
What Is an Electric Motor?
Electric motors are essential components of modern life and have been used for centuries in a variety of ways.
The basic principles behind an electric motor are fairly simple: a rotor is connected to an axle and spins when electricity is applied. The rotor is powered by electromagnetism, which generates force between the oppositely charged stator and rotor coils. This force causes the rotor to spin, creating mechanical energy which can then be used for various purposes. [1]
Types of AC motors
Most AC motors are asynchronous, meaning the rotor speed is slightly behind that of the rotating magnetic field created by the stator.
Asynchronous motors are further categorized as single-phase or three-phase.
Single phase motors require a capacitor to start and maintain rotation under load and are therefore best suited for residential applications such as pumps, fans, etc.
Three-phase motors do not require a starting capacitor and can be used in many industrial applications.
Synchronous AC motors also exist, but they tend to be more expensive than asynchronous models due to their higher efficiency ratings and ability to precisely control rotational speed without external components. Synchronous AC motors use permanent magnets embedded in the rotor, rather than relying on an electromagnet like asynchronous models. They are mainly used in precision machinery, high-speed applications, and robotics.
Induction motors are the go-to AC motor for many applications, particularly three-phase models. The stator creates a magnetic field that rotates at a higher speed than the rotor which is independent from it; this results in the rotation of motion at an ever so slightly lower rate. They can be designed in many different sizes, shapes, and power ratings to suit specific application requirements. Induction motors are capable of both low- and high-torque operation and generate relatively little heat when compared to other electric motor types.
Permanent magnet synchronous motors (PMSMs) combine features of asynchronous induction motors with permanent magnets embedded in the rotor to improve efficiency while providing torque control capabilities. PMSMs can be used in many applications including robotics, industrial tools and equipment, and automated vehicles. [2]
Brushless DC motors (BLDCs) are similar to PMSMs in that they utilize permanent magnets embedded in the rotor; however, unlike PMSMs, BLDCs use direct current instead of alternating current for power. They offer high efficiency ratings, good control characteristics, and relatively low noise levels compared to other motor types. BLDCs are primarily used in applications such as drones, robots, electric vehicles, and precision machinery.
Finally, stepper motors are brushless AC or DC motors that move a set number of degrees when commanded by an external controller. They are widely used in printing devices, 3D printers and scanners, robotic arms and other automated systems, and many other applications.
In summary, electric motors come in a variety of designs that offer unique benefits and are suited to different types of applications. Asynchronous AC motors are the most common type of motor due to their reliability, efficiency, and affordability; however, synchronous AC motors, induction motors, PMSMs and BLDCs can be more efficient or provide better control characteristics when used in certain situations. Stepper motors are also useful for precise motion control under specific conditions.
Types of DC Motors
Some types of DC motors include brushed, brushless, permanent magnet, and series wound.
Brushed DC motors use mechanical brushes to transfer electrical power from an external source to the rotor shaft. This type of motor is relatively inexpensive and has a simple construction compared to other types of electric motors. However, its performance is not as efficient as some other options due to friction between the brushes and commutator which results in wasted energy.
Brushless DC motors utilize electronic components instead of mechanical ones to provide electrical control over the rotational speed/torque of the motor. This makes them more efficient and reliable than brushed DC motors, but they are also more expensive.
Permanent magnet DC motors feature permanent magnets embedded in the rotor which can interact with the stator to generate motion. This type of motor is simpler and lighter than other options, making it attractive for applications where size and weight constraints are a priority.
Series wound DC motors have an armature winding that is connected in series with the electric power source. This allows them to develop high starting torques at low speeds, making them well suited for applications like traction drives or winching systems. However, their operating efficiency is lower due to heat losses caused by the internal resistance of the windings. [3]
Direct Drive Motors
Direct drive motors are the simplest type of electric motor. They consist of a stator, or stationary part, and a rotor, or rotating part. The stator is typically an electromagnet that generates an electromagnetic field when energized with electricity, while the rotor is usually made from ferromagnetic material such as iron. When the stator’s magnetic field interacts with the rotor’s magnetism, torque is created which causes motion in the motor’s shaft.
Direct drive motors usually have high torque at low speeds and are used in applications such as conveyor belts and other heavy machinery where precision control is needed but speed fluctuations can be tolerated. Advantages of direct drive motors include simple design, small size, durability and low cost. However, direct drive motors have limited speed range and low power output, which limits their use in certain applications.
Overall, direct drive motors are a reliable type of electric motor that can be used in many industrial applications where precision control is needed but speed fluctuations can be tolerated. They offer a simple design and construction, making them ideal for many applications where space is limited or cost-effectiveness is paramount. Their high torque at low speeds make them suitable for powering large machinery such as conveyor belts and other heavy equipment. Additionally, they are usually quite durable, and their relatively low cost makes them an attractive choice in many situations. [4]
Linear Motors
Linear motors are another type of electric motor that is used in a range of applications. A linear motor works similarly to an ordinary electric motor but instead of providing rotational motion, the output is a straight line force. Linear motors can be found in many industrial applications such as automated assembly lines, material handling systems and machine tools. They are also used in consumer products like automatic doors, vacuum cleaners and robotic arms.
Linear motors typically utilize permanent magnets arranged in either a Halbach array or a linear switched reluctance configuration to create their magnetic field, which then interacts with the current running through the stator to generate motion along its length.
In contrast to conventional rotary motors, linear motors offer higher power density and require less maintenance than other types of electric motors. They are also more accurate and can be used in a wider range of applications, including hazardous environments where combustible fuels or dust may be present.
Linear motors have become increasingly popular in recent years due to their ability to help reduce cost and increase efficiency in industrial settings. As technology continues to advance, linear motors are likely to remain an important part of many automation systems for the foreseeable future.
Servo Motors
These motors are connected to a feedback device, such as a potentiometer, encoder, or resolver, that sends signals back to the controller. This allows for precise positioning and speed control. In industrial applications, servo motors are used in robotic arms and automated machinery for assembly lines. They are also used in medical equipment such as CT scanners and ultrasound machines.
Servo motors come in many shapes and sizes depending on the application they are meant to be used for. Some common types include AC brushless servos, DC brushless servos, stepper servos, coreless servos and hobby-grade RC servos. [5]
Stepper Motors
Stepper motors are a type of electric motor that move in accurate, discrete steps. This motor is particularly useful for positioning applications because of its ability to be stopped and started at any given point in time. Stepper motors also come with a wide range of gearing choices, allowing users to achieve the desired speed and torque output according to their needs. They can also be used in robotics to allow precise positioning during assembly operations or other repetitive tasks.
As with any type of electric motor, stepper motors require careful selection based on the application’s torque requirements and the environment it will be operating in. Heat dissipation and longevity should both be taken into account when selecting a stepper motor for your project.
Hysteresis Motor
The hysteresis motor is an AC electric motor that operates on the principle of hysteresis. This type of motor has a rotor made from high-permeability material, such as nickel or iron alloy, and a stator made from low-permeability material, such as aluminum or steel. The rotor produces hysteresis losses in the stator due to its relative motion to the field set up by each alternating current half cycle.
This causes the rotor to lag behind slightly in speed compared with the stator’s magnetic field and provides torque for driving it. Hysteresis motors are commonly used for applications that require constant torque at relatively slow speeds, such as fans and pumps, because they produce little noise. They are also used in some home appliances, such as washing machines. Although the hysteresis motor is not very efficient and has a low power output, it does have the advantage of having no commutator or brushes, making them more reliable than other types of motors.
The major disadvantage of this type of motor is its tendency to draw more current during starting and running than when operating at rated speed. This can cause excessive heating and result in reduced life expectancy if it is not taken into consideration when sizing the motor for a given application. Additionally, they usually require a sophisticated control system to ensure smooth operation. [6]
Reluctance Motors
Reluctance motors are a type of motor that runs on the principle of magnetic reluctance. A reluctance motor is composed of two main parts: a stator and a rotor. The stator consists of one or more coils wound around an iron core, while the rotor is made up of multiple thin laminations with salient teeth or poles. When current is applied to the stator coils, they create a rotating magnetic field which induces torque in the rotor by creating areas of high and low magnetic reluctance.
Reluctance motors have several advantages over other types of electric motors, such as being less expensive to manufacture due to their simple design, having better speed control than traditional induction motors, and higher efficiency at partial loads. Additionally, because they use magnetism rather than electrical current to create power, they are quieter and require less maintenance compared to other motor types.
These advantages make reluctance motors an attractive choice for many applications, including industrial machinery and pumps, HVAC systems, air compressors, and electric vehicles. Reluctance motors are also used in some automotive applications such as starter motors and alternators.
Universal Motors
Universal Motors are also known as series wound motors, and they typically run on direct current. Unlike most electric motors, universal motors are suitable for both AC and DC power sources. The interchangeable nature of the power source means that these motor types can be used with a wide variety of voltage sources. Universal motors produce high torque at low speeds and often feature brushes to minimize sparking which enhances their effectiveness.
These motors tend to consume more energy than other types, making them less economical for long-term use. However, due to their versatility in terms of powering options, universal motors are commonly used in household appliances such as hair dryers or vacuums. Special care needs to be taken when handling universal motors due to their ability to reach dangerously high temperatures when pushed to the limit. [7]
FAQ
How many types of electric motors are there?
AC motors are powered by an alternating current and use electromagnets to rotate the motor’s shaft. DC motors are powered by a direct current and typically use permanent magnets as their source of magnetic fields. Special-purpose motors can refer to any type of motor designed for a specific application, such as servo or stepper motors. Other less common types of electric motor include induction, synchronous, wound rotor, brushless, linear actuator, etc. Each type is best suited for different applications based on required voltage, speed control requirements, size limitations and efficiency needs.
What is the difference between an electric motor?
The main differences between types of electric motors are the type of power used to control them and their design features. AC motors use alternating current and rely on electromagnets for their operation, while DC motors use direct current and typically employ permanent magnets in the construction. Other factors to consider include voltage requirements, speed control, size limitations and efficiency needs when choosing a motor for your application. Special-purpose motors such as servo or stepper motors may also be employed depending on your specific requirements.
What is the most common type of electric motor?
AC motors are the most common type of electric motor due to their flexibility in terms of controlling speed and torque as well as their ability to operate at high efficiency levels. AC synchronous and induction motors are often used in industrial and commercial applications, while smaller AC motors are typically seen in consumer products such as home appliances or electronic devices. DC motors remain popular due to their simple design and low cost, but they tend to be limited in terms of speed control and efficiency compared to AC motors.
What are the 3 types of AC motors?
Induction motors are the most common type of motor used in industrial applications due to their high efficiency and low cost. They operate by creating a rotating magnetic field that induces currents in the rotor windings, causing it to spin in order to generate torque. Synchronous motors use permanent magnets embedded into its rotor to create a constant rotating magnetic field. This is synchronized with the alternating current supplied from the power source, resulting in higher levels of precision as well as lower starting torques than induction motors. Servo motors provide precise control over both speed and position when given an external signal from a controller or feedback device.
Useful Video: Types Of Electric Motors – DC | AC | Synchronous | Brushless | Brushed | Stepper | Servo
Conclusion
Electric motors are one of the most important and widely used types of machinery in a wide variety of industries. They come in many different shapes and sizes, including AC induction, DC brushed, and permanent magnet motors. Each type has its own distinct advantages and disadvantages based on the application it is being used for. The selection of an appropriate motor for any given project should be considered carefully, as all types have their strengths and weaknesses depending on the task at hand. Whatever type of electric motor chosen, it can provide great efficiency gains when operated correctly. By understanding the various types available, industrial engineers and machine designers can ensure they select the best possible motor to get the job done right.
References
- https://www.parvalux.com/what-are-the-different-types-of-electric-motors/
- https://www.elprocus.com/different-types-of-electric-motors/
- https://www.automate.org/blogs/types-of-electric-motors
- https://www.iqsdirectory.com/articles/electric-motor.html
- https://www.electricaltechnology.org/2021/01/types-of-electric-motors.html
- https://blog.orientalmotor.com/motor-selection-basics-types-of-electric-motors
- https://byjus.com/physics/types-of-motors/