Basics: Electric motor

In this structure the rotor would now come to rest as soon as the opposite poles of the stator and rotor are next to each other. To stabilize the movement, the polarity must be reversed regularly. This task is undertaken by a so-called commutator. As soon as the negative and positive pole are adjacent to each other at the so-called dead center, the polarity is reversed. The negative and positive pole are now adjacent and repulse each other. The stabilization of this process can generate uniform rotation.

The three-phase motor essentially differs from the direct current motor due to the structure of the stator. This consists of three coils or a multiple thereof. The phases are therefore not displaced by 180 degrees, but by 120 degrees. If current is connected, a rotating field or so-called phase sequence is produced. This electromagnetic field rotates about the center depending on the applied frequency, and acts on the coils of the rotor, which are made to move.

The three-phase synchronous motor also functions via a rotating field. However, the rotor is set up differently. Instead of functioning via electromagnetic induction, it operates with permanent magnets. Since here, unlike the asynchronous motor, the use of permanent magnets removes the need for slip or brush contacts, the electric motor runs synchronously.

The design of synchronous electric motors has several advantages. These include:

• Particularly high efficiency – peak values of 95-96 percent at Baumüller
• High power density
• Higher speeds are possible
• Load-independent stability of the stability
• Very compact design is possible 

If permanent magnets are used, there is also no wear of the friction contacts, for example, the brushes.

A three-phase synchronous motor is used, among other things, in applications with maximum energy efficiency requirements. Typical applications are, for example, printing machines, packaging machines, textile machines, handling systems and robots.

Linear motors basically function according to the same principles as the three-phase electric motors. However, the stator is not round but is linear. The magnetic field is therefore also not a rotating field. In practice, here a rotor can be pulled back and forth over a straight rail. Curved rails are also theoretically feasible.

Due to the winding of the conductive wire in the stator, particularly the torque can be influenced. The thinner the wire the more windings that can be achieved. This has significant effects on the electromagnetic rotating field. Because the more windings there are the stronger the magnetic field. This results, for example in our Baumüller DST2 torque motors, in a significant increase in the maximum torque.

Enormous torques up to 60,000 Nm can be achieved with direct drives, and these operate with significantly less need for maintenance compared to motor-gearing combinations. However, other designs are necessary if high speeds are required, since here the torque decreases. In common high-torque applications, however, high speeds play a secondary role. Examples are winders for metal sheets that, as the reel diameter increases, depend on high torque and reduced speed. Shredders and extruders are also good application examples.

The stronger the magnetic field, the more waste heat that is also produced. To make sure that the electric motor and adjacent components do not overheat, suitable cooling is offered in many (but not all) applications. This can take place via surface, air, water, or oil cooling. Liquid cooling has particular significance in servo motors built very close to each other. As these heat each other, cooling is indispensable in most cases. However, space is also gained due to the lack of a need for fans, which would be necessary for air cooling.

The high dynamics of electric motors must also be controlled so that the potential is not wasted. This requires a servo controller, such as the Baumüller b maXX family as an interface between the electric motor or servo motor and the control unit.

Thanks to the control engineering, specific motor positions can be approached exactly and also speeds can be maintained very accurately.

In addition, high acceleration can be achieved. Specific speeds can be activated from rest in a very short time, and it is also possible to switch between specific speeds. The high dynamics and precision maxes out the full potential in the modern electric motor and allows a large number of highly specialized applications. The high precision in particular is indispensable, for example, in robotics. Baumüller servo drives are therefore used, for example, in automated production plants.

While other specifications are necessary for electrified individual mobility, Baumüller electric motors are essentially used in industrial applications. They include, for example:

• Metalworking
• Textile processing
• Packaging machines
• Recycling technology
• Medical technology
• Plastics processing
• Paper and printing machines
• Robotics

In addition, Baumüller offers drive systems for e-mobility in the commercial vehicles and work machine sectors. These include, for example, many machines for agriculture and construction, from tractors, excavators, and wheel loaders through to rollers, milling machines or crawler-mounted machines.

The electric motor has a far longer history than would be assumed today. Evidence exists of initial experiments in the 18th century. At the beginning of the 19th century, the development gathered pace as part of the fundamental study of electricity.

The specific use of electromagnetism in drives was, however, still pushed back by combustion engines during the course of the early 20th century.

Yet the physicist Moritz Hermann von Jacobi developed the first practical electric motor in 1834. Sponsored by the Russian Tsar, Nicholas I. in 1838 he operated a boat with a direct current motor for the first time, which was able to travel through St. Petersburg on the River Neva.

Today, Baumüller works on electric motors that are also designed for shipping. With high-torque synchronous motors, the specifications of then and now lie worlds apart. However, the physical operating principle has stayed the same, but continues to be developed further nowadays.

This means that diesel engines for driving the ship’s propeller in shipping can be successively replaced. Inland shipping and ferry operations between fixed charging stations are most suitable candidates. Here you will find more on the topic of the electrical ship propulsion from Baumüller.

Compared to other types of drive, such as the combustion engine, the electric motor offers numerous advantages. Several are particularly prominent within the scope of the energy transition, and the topics of environmental and climate protection. The range of advantages extends far beyond this, however. The increasing automation of agricultural and industrial processes is particularly reliant on the electric motor, which has become without alternative in this area.

The high changeability and adaptability of the electric motor makes it a type of drive with a long history and a probably even longer future.