Three-phase motors – find manufacturers and suppliers

Three-phase motors convert the electrical energy of a three-phase network into mechanical rotary motion, usually via a rotating magnetic field in the stator, which causes the rotor to rotate.

They are operated with three-phase alternating current and are robust, low-maintenance and widely used in industry, mechanical engineering and drive technology.

Here is an overview of how they work, the main types and the most important areas of application for three-phase motors and their advantages.

How three-phase motors work:

The mode of operation of three-phase motors is based on the generation of a rotating magnetic field in the stator by connecting to a three-phase alternating current network.

1. Stator field:
   The three 120° out-of-phase currents in the stator winding system generate a magnetic field that rotates continuously.
2. Rotor reaction:
   This rotating magnetic field intersects the conductors of the rotor and induces currents in them according to Faraday's law of induction.
3. Generation of force:
   The rotor currents generate their own magnetic field, which interacts with the stator field. The Lorentz force generates a torque that drives the rotor.
4. Speed:
   The speed depends on the mains frequency and the number of pole pairs of the windings and is slightly lower than the synchronous speed (slip) in asynchronous motors, while synchronous motors run exactly with the stator field.

The result is a smooth, powerful and energy-efficient rotary movement.

Main types of three-phase motors:

1. Asynchronous motor or induction motor:
   This motor is the most commonly used type of three-phase motor.
   It is so called because the speed of rotation of the rotor is not synchronized with the frequency of the current, but is slightly slower.
   The principle of electromagnetic induction is used for operation.
   Asynchronous motors are cost-efficient, robust and require little maintenance.
2. Synchronous motor:
   Unlike asynchronous motors, the rotor of a synchronous motor rotates at the same speed as the magnetic rotating field.
   They offer advantages in terms of energy efficiency and the ability to operate at a constant speed regardless of load.
   Synchronous motors are generally more expensive and more complex than asynchronous motors.

Areas of application for three-phase motors:

1. Industry and production:
Three-phase motors are the workhorses of industry, as they are used for numerous machines and processes.
Three-phase motors drive conveyor systems in factories and transport material over long distances.
Machines such as lathes, milling machines and drills use three-phase motors to drive their moving parts.
In the chemical, petrochemical and food industries, three-phase motors are used to drive pumps to transport liquids.
Air compressors, which are used for compressed air systems in production, are often driven by three-phase motors.

2. Electromobility and transportation:
The drives of trains and railroads are often based on powerful three-phase motors.
Modern three-phase motors are used in many electric vehicles, especially commercial vehicles and buses, as they are suitable for high outputs and torques.

3. Ventilation and air conditioning systems:
Three-phase motors are used in air conditioning and ventilation systems to regulate air movement.
Refrigeration compressors in industrial cold stores or air conditioning systems use three-phase motors for efficient operation.

4. Power generation:
Synchronous motors are used in power plants and renewable energy systems.
In power plants, three-phase machines are used as generators to produce electrical energy. Wind turbines also use this technology.
In hydroelectric power plants, water wheels or turbines drive three-phase generators to produce electrical energy.

5. Construction and heavy industry:
Cranes and lifting systems use three-phase motors to lift and move heavy loads.
Concrete mixers, rock crushers and other heavy construction equipment are powered by three-phase motors.
Three-phase motors drive conveyor belts and elevator systems in mining to move material from great depths.

6. Agriculture:
Pumps in large irrigation systems are often driven by three-phase motors.
In the processing of grain and animal feed, three-phase motors drive mills and crushers.
Ventilation systems in cattle stables for the supply of fresh air are also driven by three-phase motors.

7. Conveyor technology:
Three-phase motors drive automated conveyor systems to move goods.
They ensure the efficient transportation of luggage on baggage conveyor belts in airports
In automated warehouse systems, three-phase motors are used to drive storage and retrieval machines and sorting systems.

8. Elevators and escalators:
Three-phase motors provide the necessary power and reliability to transport people and goods safely between floors.
Escalators are driven by smaller three-phase motors that ensure continuous and smooth movement.

9. Water treatment and waste water plants:
In water treatment and wastewater treatment, they drive the pumps that move water between the various stages of treatment.
Three-phase motors are used to aerate clarifiers to aid the purification process.

10. Renewable energies:
Many wind turbines use three-phase generators to convert the kinetic energy of the wind into electrical energy.
Three-phase motors control the movement of solar panels so that they remain optimally aligned with the sun.

Advantages of three-phase motors:

• Three-phase motors are very efficient due to the better utilization of energy through the three-phase supply.
• Three-phase motors, especially asynchronous motors, are robust and require little maintenance.
• They are designed for continuous operation and have a long service life.
• Three-phase motors offer stable and consistent performance, which makes them particularly suitable for industrial applications.
• With the help of frequency converters, three-phase motors can be easily controlled and regulated, especially the speed.

Three-phase motors are indispensable drive units in many areas of industry, power generation, agriculture, infrastructure and mobility. They offer high efficiency, durability and flexibility, which makes them ideal for applications with high performance and load capacity requirements.

Here is a detailed overview of what to look out for when buying three-phase motors.

When buying a three-phase motor, there are a number of factors to consider to ensure that the motor is optimally suited to the respective application.

• The performance of the motor in kW or HP must match the requirements of the application. The power indicates how much work the motor can do in a given time.
• The torque in Nm is important to ensure that the motor has enough power to drive loads, especially heavy or variable loads.
• The speed in rpm indicates how fast the rotor is turning. Depending on the application, a high or low speed may be required. Many applications require variable speed control.
• Asynchronous motor (induction motor): Most commonly used as it is robust, low maintenance and cost effective. Suitable for general industrial applications.
• Synchronous motor: Used for applications that require precise speed control. Ideal for machines with constant speeds.
• The three-phase motor must match the available mains voltage. In Europe, the usual voltages are 230V/400V or 400V/690V. This may differ in other regions.
• Note the mains frequency (50 Hz or 60 Hz), as this affects the speed of the motor. A motor designed for 50 Hz runs faster at 60 Hz.
• The starting current of a motor can be up to six to eight times higher than the rated current. For applications where this current must be limited, a motor with adapted starting characteristics or a frequency inverter should be used.
• In applications where high starting currents are undesirable, a soft starter can be used to reduce the load on the mains and to start the motor more gently.
• Ensure that the motor provides sufficient torque at start-up to get the load moving, especially for machines with high inertia.
• If variable speeds are required, the motor should be compatible with a frequency converter. This enables precise control of speed and torque.
• The degree of protection (IP class) indicates how well the motor is protected against the ingress of dust and water:
• IP54: Protected against dust deposits and splash water. Suitable for many standard applications.
• IP65: Completely dust-tight and protected against water jets. Ideal for harsh environments.
• IP68: Waterproof even when permanently submerged. Used in special applications such as pumps in wet environments.
• Three-phase motors must be designed for the ambient temperatures. Some motors have special cooling mechanisms or are designed for extreme temperatures.
• If the motor is used in humid or corrosive environments, a corrosion-resistant housing or additional protection is required.
• In potentially explosive areas, e.g. in the chemical or oil industry, an explosion-proof motor in accordance with ATEX regulations is required.
• Although the higher efficiency class leads to higher procurement costs, it saves energy and costs in the long term.
• IE1: Standard efficiency.
• IE2: Higher efficiency.
• IE3: Premium efficiency (now standard in many countries).
• IE4: Super premium efficiency, even more efficient and cost-saving in operation.
• There are different types of mounting options (foot mounting, flange mounting). It is important that the motor fits the intended installation.
• The physical size of the motor must fit the machine or system into which it will be integrated. Standardized sizes facilitate replacement and retrofitting.
• High quality bearings can extend the life of the motor and minimize maintenance. With cheap motors, bearings can wear out more quickly.
• A low-maintenance motor reduces downtime and maintenance costs. Three-phase motors with robust bearings and seals often require less maintenance.
• Make sure that the motor is well cooled, especially for intensive or continuous use. Air-cooled or water-cooled motors are options, depending on the application.
• The starting current of a motor can be up to six to eight times the rated current. For applications where this current must be limited, a motor with adapted starting characteristics or a frequency inverter should be used.
• Ensure that the motor provides sufficient torque at start-up to set the load in motion, especially for machines with high inertia.
• In noise-sensitive environments (e.g. offices, hospitals, residential areas), a quiet motor should be selected. Motors with low speed or special insulation can help to minimize the noise level.
• The motor should comply with European standards and therefore have a CE mark, especially if it is sold or used in the EU.
• Ensure that the motor complies with the applicable international ISO and IEC standards, particularly with regard to efficiency and safety.
• Consider the expected service life of the motor. Robust materials, high-quality bearings and good heat dissipation contribute to a longer service life.
• It is important that spare parts are readily available and that the manufacturer or supplier provides good technical support.
• While price is an important factor, the choice should not be based on initial cost alone.
• High-efficiency motors have lower operating costs and save energy in the long run.
• A motor with low maintenance requirements reduces operating costs in the long term.

When purchasing a three-phase motor, performance, efficiency, control requirements, environmental conditions and protection class should be carefully considered. Long-term factors such as energy consumption, maintenance costs and availability of spare parts also play an important role. A well-chosen motor can lead to higher efficiencies and lower operating costs while improving the reliability and service life of the system.

Three-phase motors can be purchased from various suppliers. Comprehensive information about manufacturers and suppliers of Three-phase motors from all over the world can be found on Exportpages.