What is an Electric Motor? Structure, classification and principle of operation

The electric motor is one of the most important and popular inventions of the 20th century, playing a pivotal role in almost all areas of modern life. From familiar household appliances such as electric fans, washing machines, and refrigerators to large industrial machinery in manufacturing and construction. In this article, let’s explore in  detail what  is an electric motor  with RX Tradex? From there, learn about their structure and classification, as well as their operating principles and practical applications, helping businesses better understand this important equipment and the benefits it brings.

1. What is an electric motor?

An electric motor is an electromechanical device capable of converting electrical energy into mechanical energy. Thanks to this ability, electric motors play an extremely important role in modern life, contributing to the development of science and technology and industry.

2. Structure of electric motor

On the market today, there are many different types of electric motors, suitable for diverse models and equipment. The structure of each type of motor also has differences, below is the structure of conventional electric motors:

2.1. Static part

The static part, or stator, consists of two main parts: a steel core and a winding wire.

• Steel core: It is a magnetic conductive part, which has the shape of a hollow cylinder and is stamped from conductive steel plates from 0.35 to 0.5 mm thick. These steel plates are stamped into the shape of a towel rim, and there are grooves inside to place the winding wire before assembly.
• Winding wire: Made from copper wire or aluminum wire and placed in the grooves of the steel core. Outside the steel core, there is also an aluminum or cast iron shell to protect and secure the steel core. The lower part is a fixed pedestal with the base, and at the ends there are covers of the same material as the case. Inside the case there is a bearing (also called silver) to support the rotor spindle.

2.2. Rotating part

The rotating part, also known as the roto, consists of a steel core, a winding wire, and a machine shaft.

• Steel core: It has a solid cylindrical shape, made from electrical engineering steel plates that are stamped into forks and pressed tightly. On the surface of the steel core there are grooves for placing guides or winding wires. This steel core is tightly bonded to the spindle and is placed in the two bearings of the stator.
• Winding rope: The winding wire of the rotor has two main types: squirrel cage rotor and winding rope rotor.

• Roto winding wire: The winding wire of this type is similar to the stator winding wire, which has the advantage of generating large torque, but the structure is complex and the price is high.
• Squirrel cage rotor: This type has a different structure compared to the stator’s winding wire. It is made by casting aluminum into the grooves of the rotor, forming aluminum rods and short-circuiting at both ends. This type also has additional blades to cool when the rotor rotates. The winding rope is made from aluminum strips and two cage-shaped short-circuit rings, hence the name squirrel cage rotor. The grooves on the rotor are usually designed obliquely to the shaft to improve start-up and reduce vibration caused by intermittent electromagnetic forces acting on the rotor.

3. Working principle of electric motor

The principle of operation of electric motors is based on the phenomenon of electromagnetic induction, which is described by Faraday’s law. According to this law, when a conductive object is placed in a variable magnetic field, an induced current will appear in the conductive object.

In electric motors, when the current passes through the stator coils, a magnetic field is generated. This magnetic field acts on the coils on the rotor, generating an induced current. The induced current interacts with the magnetic field of the stator to create a moment of force, which causes the rotor to rotate.

4. Popular types of electric motors today

In today’s market, electric motors come in a variety of types and applications. Among them, the two most commonly used types are 1-phase electric motors and 3-phase electric motors. These types of electric motors all have their own characteristics and applications, suitable for different needs in industry and daily life.

4.1. 1-phase electric motor

1-phase stator winding motors use a 1-phase power supply and are usually equipped with capacitors to create the phase deviation required for operation. DC electric motors are of two main types: permanent magnet motors and excitation motors.

Permanent magnet motors use permanent magnets to generate magnetic fields, which have a simple structure and are often used in small and handheld devices. Meanwhile, excitatory motors use excitation coils to generate magnetic fields, which are adjustable, which help control speed and performance, commonly found in industrial applications.

4.2. 3-phase electric motor

Three-phase electric motor is a type of motor that uses three-phase alternating current, which is the most popular today thanks to its suitability, low cost, high durability and ease of maintenance. Three-phase motors are classified based on structural size, including three main types:

• Large motor: Has a center height of over 630mm and the outer diameter of the stator core over 900mm.
• Medium motor: With a center height of 355mm to 600mm and an outer diameter of the stator core from 560mm to 900mm.
• Small motor: There is a shaft height of 90mm to 315mm and the outer diameter of the steel core from 25mm to 560mm.

Thanks to these outstanding advantages, three-phase electric motors are widely used in many industrial and civil sectors.

5. Some applications of electric motors

Electric motors are widely used in almost every field, from small household appliances such as microwave ovens and recorders to hand tools such as drills. They are common in household appliances such as electric fans, refrigerators, washing machines, vacuum cleaners, and water pumps.

The power of the electric motor is also an important factor for the operation of elevators and ventilation systems. In the field of transportation, electric motors are used in many types of vehicles, especially locomotives in many countries around the world. In addition, in computer technology, electric motors play an important role in the operation of hard disk drives and optical drives.

6. Conclusion

It can be seen that, thanks to its diverse applications, electric motors are considered an important equipment, making a great contribution to the development of life in general and in the manufacturing industry in particular. Understanding what an electric motor is, its structure and principle will help you use equipment efficiently, safely and energy-saving, contributing to improving your production efficiency.

If you are interested in learning more about advanced electric motor technologies, as well as want to discover the latest products, machinery and equipment in the manufacturing industry, you can register to participate in the Vietnam Manufacturing Expo 2024. This event is a great opportunity to connect with leading experts, stay up-to-date with the latest technology trends, and find optimal solutions for your business’s manufacturing operations.