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How do you set and keep things in motion without any muscle power? While mechanical energy in a steam engine is generated with the help of hot steam, or rather steam pressure, an electric motor uses electrical energy as its source. This is why it is also referred to as an electromechanical converter.
The counterpart to the electric motor is the similarly constructed generator. It transforms mechanical kinetic power into electrical power rating. The physical basis for both is the electromagnetic induction. Current is induced in the generator and electrical energy is generated when a conductor is in a moving magnetic field. In the electric motor, on the other hand, a current-carrying conductor induces magnetic fields. Their mutual forces of attraction and repulsion are the basis for generating movement.
The inner workings of an electric motor basically consist of the stator and the rotor. The term "stator" is derived from the Latin verb "stare" = "to stand still". This is the immovable component of an electric motor. It is firmly connected to the housing, which is also immobile. In contrast, the rotor sits on the motor shaft and is movable (rotatable).
In an AC motor, the stator contains the so-called laminated core, which is wrapped with copper wires. This winding acts as a coil and, when current flows through it, generates a rotating rotating magnetic field. This magnetic field created by the stator induces a current in the rotor, which in turn creates an electromagnetic field around the rotor. This causes the rotor and motor shaft to rotate and follow the rotating field of the stator.
The task of the electric motor is to use the resulting rotary motion to drive a gear unit (torque and speed converter) or, as a mains motor, to drive an application directly.
All inventions began with the DC motor. Nowadays, however, the AC motors in various mounting positions are the most common electric motors in industry today.. What they all have in common is the resulting rotary movement of the motor axis. The operating principle of AC motors is based on the electromagnetic operating principle of the DC motor.
As with most electric motors, the DC motor consists of a fixed part, the stator, and a rotatable component, the rotor. The stator consists of either an electromagnet, which is used to induce a magnetic field, or permanent magnets, which permanently generate a magnetic field. Inside this stator is a rotor, also known as an armature, which is wound around a coil. If the coil is connected to a DC source (a battery, an accumulator or a DC voltage power supply), it forms a magnetic field and the iron core of the rotor becomes an electromagnet. The rotor is rotatable and aligns itself in such a way that the attracting, i.e. unequal poles of the magnetic field are opposite each other - the north pole of the armature is opposite the south pole of the stator.
In order to set the rotor in a continuous rotary motion, the magnetic alignment must be repeatedly reversed. This is done by changing the direction of the converter in the coil. For this purpose, the motor has a so-called commutator. The two supply contacts are connected to this and it takes on the task of reversing the polarity. The alternating forces of attraction and repulsion ensure that the armature / rotor continues to turn.
DC motors are mainly used in users with low power ratings. These include smaller tools, hoists, lifts or electric vehicles.
Instead of direct current, an AC motor requires three-phase current, i.e. three-phase alternating current. In an asynchronous motor, the rotor is a so-called squirrel-cage rotor. The rotation results from the electromagnetic induction of this rotor. For this purpose, the stator phase of the three-phase current, windings (coils) are offset by 120° (arranged in a triangular shape). arranged. When connected to the three-phase current, these coils each build up a magnetic field that rotates to the rhythm of the time-shifted line frequency. The electromagnetically induced rotor is carried along by these magnetic fields and rotates. In this way, a commutator is not required as in the DC motor.
Asynchronous motors are also called induction motors as they only function via electromagnetic induced stress. They run asynchronously because the circumferential speed of the electromagnetically induced rotor never reaches the rotating speed of the magnetic field (rotating field). The efficiency of asynchronous AC motors is lower than that of a DC motor due to this slip.
In synchronous motors, the rotor is assembled with permanent magnets instead of windings or conductor bars. In this way, the electromagnetic induction of the rotor can be omitted and the rotor rotates synchronously without slip at the same circumferential speed as the stator magnetic field. The efficiency, power density and possible rotational speeds of synchronous motors are therefore significantly higher than those of asynchronous motors. However, the design of synchronous motors is also significantly more complex and expensive.
In addition to the rotary machines that are predominantly used in industry, drives are also required for movements on straight or curved paths. Such motion profiles are mainly found in machine tools as well as positioning and handling systems.
Rotary electric motors can also convert their rotary motion into a linear motion with the help of a gear unit, i.e. indirectly. However, they often do not have the necessary dynamics to realise particularly demanding and fast "translatory" movements or positioning.
This is where linear motors come into clearance, which generate the translatory movement directly (direct drives). Their operating principle can be derived from rotary electric motors. Imagine a rotary motoring operation "unfolded": The previously round stator becomes a flat route (race or rail) that is travelled. The magnetic field then forms along this path. The rotor, which corresponds to the rotor in an AC motor and rotates in a circle, is pulled along the route as a so-called carriage or translator by the longitudinally moving magnetic field of the stator in a straight line or in curves in a linear motor.
The invention of the electric motor cannot be attributed to a single person. Its discovery was the result of the research of several inventors. In the 19th century, interest in electrical engineering continued to grow and inspired researchers worldwide. New inventions appeared one after the other.
As the first electric motors relied on a current supply of zinc batteries, there was still a long way to go before they could seriously compete with the prevailing steam engines. This changed with the development of the first electricity generators.
But here, too, there were limitations. The direct current produced by the generators could not be transported over long distances. The breakthrough only came with the introduction of alternating and three-phase current, which could be supplied over long distances without major losses, and with the invention of the AC motor.
Here is a brief, but not complete, insight into the historical facts and figures:
It all started with electric motors. Electric motors are still one of our core businesses - mostly in the form of gearmotors and in connection with frequency inverters suitable for the application. As a leading global manufacturer of drive and automation solutions, we offer you a wide range of asynchronous and synchronous motors. Whether energy-efficient motors, linear motors, electric cylinders, motors in hygienic or explosion-proof design, low-voltage drives, etc. - you are sure to find the optimum electric motor solution for you. Extensive accessories such as brakes, built-in encoders and other options round off our motoring operation programme.