Lexicon and terms for electric motors | Fischer electric motors


Brushless motors (DC machine)

A DC machine is an electric motor that is powered by direct current, or a generator that conversely transforms mechanical energy into AC voltage and then rectifies it. In some applications, a device can also perform both functions.

Built-in motors

In the built-in motor, the active motor parts – the stator with winding and the rotor with shaft – are installed in the customer housing or machine part.

Drive systems

In technology, drive designates the structural unit that drives energy transformation by means of a machine. It is often a motor with the necessary transmission. There are rotary drives and linear drives.

Drum motors

Drum motors are modern drives that combine the gear motor and drive drum in a fixed unit. Drum motors were developed as a drive for belt conveyors. Through continuous further development and the use of state-of-the-art materials, drum motors are also used for completely different applications. In general, a drum motor can also be used wherever a drum is currently driven by an external gear motor.

Disc rotor motors

A disc rotor motor is an electric motor whose rotor has the shape of a disc (which is why the disc rotor motor is also known in English as a “pancake motor”). In the best-known design, the conducting windings are mounted in the housing. Disc rotor motors are easily recognisable by their design, which is unusual for electric motors (diameter is greater than the length).

Direct drives

Direct drives are drives in which the electric machine and the working machine are directly connected. The motor is designed in such a way that its speed is the same as that of the working machine; no transmission is required.

Typical examples of direct drives are stationary grinding machines, fans, water pumps, linear drives and torque motors.

Electric motors

Electric motors are electromechanical converters that convert electrical energy into mechanical energy. In electric motors, the force exerted by a magnetic field on the conductors of a coil through which current is flowing is converted into motion. Electric motors are the counterpart to the generator. Electric motors usually generate rotary movements, but they can also perform translatory movements. Electric motors are used to drive various working machines and vehicles.

Freely programmable direct drives

Synchronous servo motors, torque motors, linear motors. These are operated via an electronic controller. This allows the speed, torque or position to be freely selected.

Frequency converters

are devices based on power semiconductor components that operate in switching mode, i.e. only in the conducting state or in the blocking state. They have the task, especially in speed-adjustable three-phase drive systems, to generate a typically three-phase voltage with a variable frequency and voltage amplitude for powering the three-phase motor from a single-phase or three-phase mains AC voltage with a constant frequency and amplitude. Previously, grids with different frequencies were coupled via rotating frequency converters. However, mechanical systems are still used in railway converting stations.

Geared motor

A geared motor is a combination of a motor (usually an electric motor) and a gearbox. It ensures that in most cases the output shaft rotates at a lower speed but with a considerably higher torque than that of the motor.

High-speed motors

High-speed motors run much faster than standard motors. There are motors that reach over 100,000 rpm, for example when used in electric turbochargers. This is achieved by a supplying power from frequency converters with a feed frequency of several hundred Hz to over 1000 Hz. The motor is smaller than a standard motor with the same power rating. The rotating parts sometimes have to withstand considerable radial accelerations (centrifugal force).

Further examples:

  • Spindle drive for textile machines: integrated directly into the spindle, highly dynamic
  • Motor spindles for machine tools
  • Turbo pump (vacuum pump): 1 kW, 39,000 rpm
  • Electric turbocharger: speed 130,000 rpm

Linear motor

According to the principle, every type of rotary electric motor known can also be realised in a stretched arrangement as a linear motor. IIn the usual version as a synchronous motor or asynchronous motor, a linear motor consists of only two parts; a winding package and a secondary part. Magnetically operated linear motors are available in flat and cylindrical versions, air and water-cooled and with different guide systems. They are the means of propulsion for translatory direct drive technology. They enable direct, low-wear and low-vibration force feeding into longitudinally movable machine parts without prior conversion from a rotary motion sequence.

Motor geometry

The most important geometric properties and dimensions of the classic motors are shown in the motor geometry.

Motor parameters

By optimising various motor parameters, power and torque are increased by up to 30%, while reliability and driveability remain unchanged.


Liquids, gases or mixtures are conveyed with a pump. The drive work into the kinetic energy of the medium is converted for this purpose. Pumps accordingly belong to the fluid energy machines.

Saw motor

Saw motors are machines that use electric motors to drive circular saw blades. The saw blade diameter can range from about 20 cm to about 500 cm.

Servo converters/servo drives

Servo drives contain a servo motor, the servo converter with power electronics and controller as well as gearboxes for speed adjustment or for converting the rotary movement into a linear movement. The servo converter supplies power to the servo motor. In addition to the power electronics, the servo converter contains a highly dynamic controller for current, speed and position. The servo converter’s equipment also includes evaluation electronics for the motor’s position sensor as well as an interface for communication with the machine controller.

Spindle drives

Spindle motors are converter-controlled three-phase asynchronous motors or synchronous motors for driving machine tool spindles for grinding, milling and engraving tasks as well as for applications in drilling automation. The drive elements for linear actuators are also called spindle motors. In the synchronous motor or stepper motor version, they are used in conjunction with an integrated threaded spindle for the direct conversion of rotary movements into translatory movements.

Synchronous motors

A synchronous motor is a synchronous machine in motor operation in which a constantly magnetised rotor is carried along synchronously by a moving magnetic rotary field in the surrounding stator. The running synchronous motor moves synchronously with the AC voltage – its speed is thus linked to the frequency of the AC voltage via the pole pair number.

Synchronous disc rotor motor

see disc rotor motor.

Tool changer

A tool changer in a machining centre is a mechanical device for the automatic exchange of tools or process-related aids. With the tool changer, tools are exchanged between the tool magazines and the machining spindles. The change process is done with single or double grippers or from the magazine to the spindle (pick-up changer). EThe tool change time is a measure of the speed of the tool changer.

Torque motor

Torque motors are rotary drive elements for direct drive technology. In modern versions, these are brushless synchronous motors with high-pole permanent magnet excitation in an internal or external rotor design. In the machine tool industry in particular, they serve as a replacement for hydraulic and conventional electric drive structures consisting of an electric motor and a gear unit. They are designed for high torques (up to a few thousand Newton metres, Nm) and low speeds, and their mechanical concept is designed to make them easy to integrate into the mechanisms and machines to be driven.

Water-cooled motors

Electric motors are traditionally cooled with air. Liquid cooling has already been used for some time for very large machines. However, liquid cooling can also be highly beneficial in the lower power range (<50 kW).

The dissipated heat of the motor is removed by the cooling medium and thus does not burden the immediate environment. This is particularly advantageous for:

  • precision machines
  • unfavourable installation conditions (no air circulation
  • high ambient temperature
  • air-conditioned rooms

Well pumps

Underwater motor pumps have developed from water-filled underwater motors. The water-filled underwater motors were developed in 1928 by Mr F.W. Pleuger. In the same year, the Pleuger underwater pumps were used for the first time in the construction of the Berlin underground railway for groundwater subsidence. In the further course, the Pleuger company was the driving force behind many other trailblazing developments. For this reason, we still speak of “Pleuger pumps” when underwater motor pumps are meant.

Underwater pumps are suitable for:

  • Drinking water supply
  • Water supply in dairies, breweries and mineral water bottlers
  • Domestic water supply
  • Groundwater heat pump systems
  • Irrigation systems in horticulture, agriculture and forestry
  • Fountain systems, also for horizontal installation
  • Pressure-boosting systems with pump in pressure jacket
  • Water management in underground construction and mining
  • Water supply of industrial cooling circuits