Home » Choosing the right electric motor

An electric motor is an electromechanical device that converts electrical energy into mechanical energy. Most often, the movement is rotary, with mechanical energy characterized by rotational speed and motor torque.

This buying guide will only cover this type of motor. Linear motors will be covered in another buying guide.

It is estimated that electric motor systems account for 46% of the world’s electricity consumption. In industry, electric motors are everywhere. They run pumps, drive compressors and conveyors  and operate fans, blowers, drills and mixers. Electric motors are at the very heart of industry.

Electric motors make it possible to perform different types of movement: fast, precise, continuous, with or without gear shifting, etc. All of these applications require their own motor technology.

These two types of motors are built differently:

AC motors are the most popular in the industry as they have several advantages:

Because of how they operate, which involves synchronization between the rotor rotation and current frequency, the speed of AC motors remains constant. They are particularly suited for applications requiring continuous movement and few gear changes. This type of motor is therefore perfectly adapted for use in pumps, conveyors and fans.

They can also be integrated into systems that do not require high accuracy if they are used with variable speed.

On the other hand, speed control functions make them more expensive than other motors.

There are two types of AC motors: single-phase and three-phase.

DC motors are also very common in industrial environments because they have significant advantages depending on the format (see brushless motor question):

They are very well suited for dynamic applications requiring high accuracy particularly in terms of speed, as in the case of elevators, or in terms of position as in the case of robots or machine tools.

They can also be advantageous for applications requiring high power (10,000 kW for example).

However, they have certain disadvantages depending on their structure compared to AC motors:

3. What are the market trends today?

The two most common types of DC motors are brushed motors and brushless motors.

Brushed motors are the simplest and most frequently used motors, especially for basic industrial equipment and low-budget applications.

There are four types of brushed motors depending on your intended use.

All brushed motors have significant disadvantages however:

Brushless motors make up for some of the weak points of brushed motors, such as the presence of brushes. But these motors also have other advantages:

The fact that these motors are able operate at very high speeds makes them particularly suitable for grinders, fans or saws.

Brushless motors are systematically equipped with an encoder, a sensor that allows for electronic switching and determination of the rotor position. These motors are therefore perfect for servomotor precision applications.

However, they have certain disadvantages:

Is this the end of brushed motors? Not according to the Opportunity rover

It might seem that in the match between brushed motors and brushless motors, the brushed ones would lose and have no choice but to go back to the closet. This is not the case, however, as brushed motors remain popular in industry and even in space. Maxon, a Swiss manufacturer of electric motors, is constantly developing new technologies for brushed motors and their brushed motors equipped Opportunity, NASA’s rover sent to Mars in 2003.

Opportunity took 34 DC brushed motors onbord which have been able to operate successfully under extreme conditions with wide temperature variations. NASA’s choice was simple: to benefit from the simplicity of brushed motor control and therefore have the ability to control all 34 motors from a single controller. Brushless motors would have required one controller per motor with risks of costs and complications.

A stepper motor converts an electrical pulse into an angular motion. It is useful for applications requiring open loop position control.

There are three categories of stepper motors:

Permanent magnet and hybrid motors are the most commonly used motors because they have certain advantages:

However, they also have some disadvantages:

When selecting a stepper motor, it is important to take into account:

Manufacturers are increasingly contemplating the question of energy efficiency. A greener and more environmentally friendly economy is one of the objectives of the 2015 United Nations Climate Change Conference which many States committed to. But it is above all in order to limit consumption and for savings that industry has been acquiring more energy-efficient equipment in recent years. According to a study by the European Commission, motors account for 65% of industrial energy consumption in Europe . Taking action when it comes to motors is therefore an important step in order to reduce CO2 emissions. The Commission even predicts that it is possible to improve the energy efficiency of European-made motors by 20 to 30% by 2020 . The result would be 63 million tonnes less CO2 in the atmosphere and 135 billion kWh saved.

If you also want to integrate energy-efficient motors and get savings while contributing to the planet, you will first need to look at the energy efficiency standards for motors in your country or geographical area. But be careful, these standards do not apply to all motors, only to asynchronous AC electric motors.

The EU has already adopted several directives aimed at reducing the energy consumption of motors, including the obligation for manufacturers to place energy-efficient motors on the market:

In the United States, the standards defined by the American association NEMA (National Electrical Manufacturers Association) are in force. Since 2007, the minimum level required has been set at IE2. The same classification applies to Australia and New Zealand.

In China, the Korean MEPS (Minimum Energy Performance Standard) standards have been applied to small and medium-sized three-phase asynchronous motors since 2002 (GB 18693). In 2012, MEPS standards were harmonized with IEC standards, moving from IE1 to IE2 and now to IE3.

Japan has harmonized its national regulations with IEC efficiency classes and included IE2 and IE3 electric motors in its Top Runner program in 2014. Introduced in 1999, the Top Runner program forces Japanese manufacturers to constantly offer new models on the market that are more energy efficient than previous generations, thus forcing emulation and energy innovation.

India has had a comparative efficiency label since 2009 and a national standard at an IE2 level since 2012.

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