Electrical machine

An electrical machine is used in the electric power engineering machine and represents a form of energy conversion dar. is made between rotating electrical machines, these include various types of electric motors and generators, and stationary electrical machines, to which only transformers are distinguished. All electrical machines is that they have in their construction a magnetic circuit, which is essential for the function.


Electrical machines utilize the properties of the electromagnetic interaction and based on the electromagnetic induction and magnetic force effects which by the Lorentz force, and is described in some types of machines by the reluctance force.

Referred to the group of static electrical machines, or as a passive electrical machines include historical reasons only the transformers and since in particular transformers which are used in the field of electrical power engineering such as power transformers. In resting electrical machines, the magnetic force effects play only a minor role or undesirable, since it no movements are executed and the function of a transformer is to transform AC voltages between different high voltage levels.

In the main larger and exclusively shown in the following field of rotating electrical machines, which is characterized by a variety of different designs and applications, the magnetic force effects play a central role. They are used for converting electrical power to mechanical power to a shaft. Electric power is converted into mechanical power is referred to as an electric motor, in the opposite direction of mechanical power is converted into electric power, is called an electric generator. Some electrical machine types can be operated as a motor or as a generator also, the specific function is determined by the operating range of the machine. Because of this, it also comes in the conceptual use of a motor or generator to overlap.

Each energy change is associated with a loss of energy in the form of heat. One advantage of electrical machines is that their losses are relatively small, so they achieve a high efficiency. Electrical machinery, can achieve efficiencies of up to 99%.

On receiving the electrical machinery industry is the industrial electrical engineering. Electrical machines are used today in all areas of technology, industry, everyday, transport, medicine and other areas. The power range extends from electrical machinery orders of magnitude less than one microwatt (eg movements, micro systems ) to beyond one gigawatt ( 1GW = 1,000,000,000 watts) as the turbo-generators used in power plants.


Electrical machines are which are traversed by the electric current from different windings arranged. Thereby occurring the magnetic flux is guided in a magnetic circuit, which is also referred to as an iron core, specifically. This core is made from materials which can conduct the magnetic flux material, for example of layered magnetic steel sheet. The stratification is used to avoid undesirable eddy currents. Parts of said magnetic circuit represents the stator and the rotor, referred to in some machines as anchors. The magnetic forces act on these different parts of the core and in turn lead to movements of the machine parts.

For electrical insulation of current-carrying parts against each other and against the external environment to electrical machines have the isolation regions. For mechanical stabilization and support of the machine and possibly the guidance of the moving parts, they have more and varied mechanical construction parts such as bearings.


A breakdown of rotating electrical machines can be made according to different criteria, the divisions are not in the literature characterized by uniform and overlap. The classification which can generated by corresponding spatial winding arrangement a rotating magnetic field, carried out according to the type of current used as DC, AC and three-phase alternating current, a multi-phase alternating current. Another classification, the operation of the machine and relate to division into commutator, asynchronous and synchronous machine. Each of these groups consists of several different types of machines which are divided into further classes.

The following table is an example and not complete classification according to type of current in the vertical direction and after action principle in the horizontal direction, together with the indication of possible areas of application, compiled as a simple overview.

Asynchronous and synchronous machines require for their motor operating polyphase alternating current or produce as a generator polyphase alternating current. Typically, this is three-phase alternating current which generates a rotating field in the region of the rotor. There are also three-phase machines that are operated, for example, two-phase alternating-current, this is the case with some stepping motors. The induction machine with squirrel-cage rotor is widely used as a drive, as low cost and low maintenance. Characteristic of the induction machine is the slip, which causes the rotor does not move with the same rotational speed as the rotating magnetic field.

The group of synchronous machines is characterized by a rigid relationship of rotor rotation with the rotating field. Examples of synchronous machines are the salient, which broken down into internal and external pole, and the Vollpolmaschinen, which are in the form of turbo-generators in power plants use. The synchronous motors are stepper motors and the specific embodiments, such as the Lavet stepping motor and the DC brushless motors as it also represents the torque motor. These synchronous motors, the rotating field is generated by a frequency necessary addition to the engine with a four-quadrant controller. For outputs, the process of how the Blockommutierung be used for higher power working through techniques such as vector control and space vector modulation.

In addition, there are special induction machines, such as the cascade machine, for example, as a generator in wind turbines is used. An inserted in nanotechnology engine is the electrostatic motor.

The commutator motors can be operated with the help of the commutator directly to direct current or single-phase alternating current. Examples of commutator machines are the DC machine and universal motor which can be powered by DC or AC voltage. The DC machines are divided into the bypass machine and the series -wound machine.

In addition, there are electric machines with only limited application areas such as the Unipolarmaschine that without rectification directly supplies the generator mode, a DC voltage. A historical design of a Unipolarmaschine represents the Barlow - wheel dar. In addition, there from the beginning of the electrical historical electrical machines which have found little or no spread because of various disadvantages. These include the Egger- electric motor.