Electric drive
An electric drive is a drive having one or more electric motors , which from a control is regulated. If the engine power is high, electronic power actuators are interposed between the control and the electric motor (or the electric motors). They are then part of the electric drive.
The regulation of the electric drive is often carried out in the form of a speed , torque , position, speed or more variable regulation. One or more other control loops may or may not be subordinate to a control loop .
For practical operation, separate components for switching the drive on and off as well as necessary safety and monitoring devices, as well as an energy source in the form of a mains connection , a generator (e.g. in the form of a fuel cell ), a traction battery or a double-layer capacitor (e.g. in the form of a of ultra- or super caps provided).
Functions, motion aspects and control implementation
With an electric drive, electrical energy is converted into mechanical kinetic energy. This can be converted into a rotary movement as well as into a linear movement ( linear drive or regulated rotating electric motor with flanged worm gear ). In the case of electric drives, the elementary movements "rotation" and "translation" are not uniform movements, especially for position control. Rather, one or more defined movement sequences (that is, movement patterns as a function of time) are specified by the respective regulation. With torque and speed control , things are different, at least at intervals: in a certain interval, a certain movement can be carried out uniformly.
In professional use today, drive controls are implemented digitally. Only in the hobby area (e.g. in model making ) or in rare cases in the area of small drives are regulations still implemented analogously. In terms of hardware, in the case of digital implementations, microcontrollers with input / output units with analog-digital and digital-analog converters as well as communication interfaces are used. In terms of software, drive controls are implemented in the form of direct digital control algorithms, supplementary controls (e.g. for sensors and actuators) in the form of input / output control commands and communication exchange in the form of interface communication routines.
Power electronic actuators
Efficiency and practical operating characteristics
Compared to other types of drive (e.g. internal combustion engine ), electric drives are very efficient . Efficiencies of up to 99% are not uncommon for large machines. A distinction is made between drives with lower power (small electrical drives) and those with higher power. In the power range of approx. 900–1,100 watts, electric drives typically have an efficiency of 70–90%. The efficiency can, however, increase by up to 99% with increasing power (growth laws of electrical machines). In contrast to petrol or diesel drives, electric drives have a lower dead weight in relation to their power and also generate no local emissions and are more reliable than their counterparts. In addition, they can be stopped immediately in emergencies by switching off the electrical network (subject to the rotating masses running out due to the moment of inertia ).
Areas of application
The areas of application range from small drives with a few milliwatts of power (e.g. drive motors for CD players) to medium-power applications (vacuum cleaners, kitchen appliances) to the highest outputs in industry and transport (drives for coal mills, drives for electric trains, underground Lanes etc.).
The possibility of being able to use solar energy with the electric drive will probably make the drive indispensable for the future. Electric drives in the transport sector are to be separated from the energy supply with regard to the chances of success. While battery electric vehicles (BEVs) outside of locally operating vehicles (operation in the interior or on courtyards) have so far not been successful, the electric drive is found in overhead line-powered systems ( trolleybus , electric locomotive ), in diesel-electric drives , hybrid-electric vehicles ( hybrid drive ) but also fuel cell vehicles a wider spread. New leaps in performance in accumulator technology, e.g. For example, the lithium-ion battery or the lithium titanate battery with nano-technology open up new market opportunities for electric vehicles in the context of electromobility .
June 2017 the world's first ferry (100 tons, 23 m length) with battery-electric drive goes into operation in Taiwan . Electric motors have long been used for swiveling ship drives (pods) and quickly controllable bow thrusters. Power is supplied by diesel or LNG-powered generators. Submarines could sometimes be powered electrically in order to avoid the noise emissions from internal combustion engines . Nuclear submarines run on an electric motor. Restrictions on internal combustion engines on inland waters due to noise and pollution encourage electric boats . Model airplanes and especially small drone multicopters fly battery-powered.
history
In the early days of industrialization, the electric motor soon replaced the steam engine as well as wind and water mills . This happened as soon as the distribution of electrical energy was available. Right from the start, electric motors were more reliable than competing drives.
In the beginning, a central motor was installed per factory hall. The rotary energy was distributed to the individual machines with long transmission shafts. The transmission belt (sometimes several meters long) was usually thrown off or put on while the shaft was running. Accidents occurred here. Further development made it possible for each machine to have its own electric motor. The transmissions disappeared in a short time. A specialization for special machines (e.g. rolling mills ) or areas at risk of explosion followed quickly . The number of electric motors per machine or system grew steadily. Mass production made the electric motor inexpensive.
One can currently observe that the electric motor is not only assigned the drive task, but also the reliable positioning of (mostly linear) machine movements. For this purpose, servo motors used with the associated control units. Together with the new concepts for the control and automation of a machine, one can observe a stormy technical development here.
World record
A new world record was achieved in 2008, when researchers at ETH Zurich developed an electric drive system with one million revolutions per minute in collaboration with German companies, engine manufacturer ATE GmbH and ball bearing manufacturer myonic GmbH. This is the highest speed ever achieved by an electric drive system.
literature
- Manfred Meyer: Electric drive technology. Springer, Berlin, 2 volumes, volume 1: Asynchronous machines in mains operation and speed-controlled slip-ring machines. 1985, ISBN 3-540-13852-8 , Volume 2: Converter-fed direct current machines and fully converter-fed three-phase machines. 1987, ISBN 3-540-17022-7
- Ulrich Riefenstahl: Electric drive systems: Fundamentals, components, control methods, motion control. 2., arr. and exp. Ed., Teubner, Wiesbaden 2006, ISBN 3-8351-0029-7
- Werner Böhm: Electric drives (Kamprath series), 5th, revised. and additional ed., Vogel Fachbuch 2002, ISBN 3-8023-1912-5
- Rolf Schönfeld: Electric drives - motion analysis, torque control, motion control. Springer, Berlin Heidelberg 1995, ISBN 3-540-59213-X
- Gert-Helge Geitner: Design of digital controllers for electric drives. VDE-Verlag, Berlin Offenbach 1996, ISBN 3-8007-1847-2
- Nguyen Phung Quang, Jörg-Andreas Dittrich: Vector Control of Three-Phase AC Machines. Springer, 2008, ISBN 978-3-540-79028-0
Web links
Individual evidence
- ↑ greenfleet . greenfleet.info. Archived from the original on February 12, 2006. Retrieved March 25, 2019.
- ↑ Visedo powers Asia's first E-ferry in Taiwan ( Memento November 11, 2017 in the Internet Archive ) visedo.com, June 16, 2017, accessed November 11, 2017.
- ↑ "Highest speed in the world" - article on FOCUS ONLINE
- ↑ "Electric drive systems - world record by researchers at ETH Zurich" - article on innovations-report.de
- ↑ “One million revolutions per minute” - article on handelsblatt.com
- ↑ “One million revolutions per minute” - article on ethlife.ethz.ch
- ↑ "Celeroton world record: 1 million revolutions per minute" - article on nachrichten.ch