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Electromechanics

From Wikipedia, the free encyclopedia

In engineering, electromechanics[1][2][3][4] combines processes and procedures drawn from electrical engineering and mechanical engineering. Electromechanics focuses on the interaction of electrical and mechanical systems as a whole and how the two systems interact with each other. This process is especially prominent in systems such as those of DC Machines which can be designed and operated to generate power from a mechanical process (generator) or used to power a mechanical effect (motor). Electrical engineering in this context also encompasses electronics engineering.

Electromechanical devices are ones which have both electrical and mechanical processes. Strictly speaking, a manually operated switch is an electromechanical component due to the mechanical movement causing an electrical output. Though this is true, the term is usually understood to refer to devices which involve an electrical signal to create mechanical movement, or vice versa mechanical movement to create an electric signal. Often involving electromagnetic principles such as in relays, which allow a voltage or current to control another, usually isolated circuit voltage or current by mechanically switching sets of contacts, and solenoids, by which a voltage can actuate a moving linkage as in solenoid valves.

Before the development of modern electronics, electromechanical devices were widely used in complicated subsystems of parts, including electric typewriters, teleprinters, clocks, initial television systems, and the very early electromechanical digital computers.

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Transcription

Electrical engineering jobs are lucrative, competitive positions for some of the brightest minds out there. Companies that hire electrical engineers are hiring for the future of their company. Without electrical engineers, their products are services are not going to be completed successfully. They are a crucial part of the businesses that hire them. Electrical engineering, like any job in technology, contains a lot of technical questions. Your safest bet to succeed at an electrical engineering interview is to brush up on your technical knowledge and review any of the latest updates in the field. You are going to be tested on what you can do, because your job is too important to be given to someone without the right technical knowledge. In this video are some of the questions you may be asked at a job interview, including a few technical questions to get you started. 1. Why star delta starter is preferred with induction motor? Star delta starter is preferred with induction motor due to following reasons: Starting current is reduced 3 4 times of the direct current due to which voltage drops and hence it causes less losses. Star delta starter circuit comes in circuit first during starting of motor, which reduces voltage 3 times, that is why current also reduces up to 3 times and hence less motor burning is caused. In addition, starting torque is increased and it prevents the damage of motor winding. 2. State the difference between generator and alternator? Generator and alternator are two devices, which converts mechanical energy into electrical energy. Both have the same principle of electromagnetic induction, the only difference is that their construction. Generator persists stationary magnetic field and rotating conductor which rolls on the armature with slip rings and brushes riding against each other, hence it converts the induced EMF into dc current for external load whereas an alternator has a stationary armature and rotating magnetic field for high voltages but for low voltage output rotating armature and stationary magnetic field is used. 3. Why AC systems are preferred over DC systems? Due to following reasons, AC systems are preferred over DC systems: a. It is easy to maintain and change the voltage of AC electricity for transmission and distribution. b. Plant cost for AC transmission (circuit breakers, transformers etc) is much lower than the equivalent DC transmission. c. From power stations, AC is produced so it is better to use AC then DC instead of converting it. d. When a large fault occurs in a network, it is easier to interrupt in an AC system, as the sine wave current will naturally tend to zero at some point making the current easier to interrupt. 4. How can you relate power engineering with electrical engineering? Power engineering is a sub division of electrical engineering. It deals with generation, transmission and distribution of energy in electrical form. Design of all power equipments also comes under power engineering. Power engineers may work on the design and maintenance of the power grid i.e. called on grid systems and they might work on off grid systems that are not connected to the system. 5. What are the various kind of cables used for transmission? Cables, which are used for transmitting power, can be categorized in three forms: Low-tension cables, which can transmit voltage upto 1000 volts. High-tension cables can transmit voltage upto 23000 volts. Super tension cables can transmit voltage 66 kV to 132 kV. 6. Why back EMF used for a dc motor? Highlight its significance. The induced EMF developed when the rotating conductors of the armature between the poles of magnet, in a DC motor, cut the magnetic flux, opposes the current flowing through the conductor, when the armature rotates, is called back EMF. Its value depends upon the speed of rotation of the armature conductors. In starting, the value of back EMF is zero. 7. What is slip in an induction motor? Slip can be defined as the difference between the flux speed (Ns) and the rotor speed (N). Speed of the rotor of an induction motor is always less than its synchronous speed. It is usually expressed as a percentage of synchronous speed (Ns) and represented by the symbol "S". 8. Explain the application of storage batteries? Storage batteries are used for various purposes, some of the applications are mentioned below: For the operation of protective devices and for emergency lighting at generating stations and substations. For starting, ignition and lighting of automobiles, aircrafts etc. For lighting on steam and diesel railways trains. As a supply power source in telephone exchange, laboratories and broad casting stations. For emergency lighting at hospitals, banks, rural areas where electricity supplies are not possible. 9. Explain advantages of storage batteries? Few advantages of storage batteries are mentioned below: Most efficient form of storing energy portably. Stored energy is available immediately because there is no lag of time for delivering the stored energy. Reliable source for supply of energy. The energy can be drawn at a fairly constant rate. 10. What are the different methods for the starting of a synchronous motor? Starting methods: Synchronous motor can be started by the following two methods: By means of an auxiliary motor: The rotor of a synchronous motor is rotated by auxiliary motor. Then rotor poles are excited due to which the rotor field is locked with the stator-revolving field and continuous rotation is obtained. By providing damper winding: Here, bar conductors are embedded in the outer periphery of the rotor poles and are short-circuited with the short-circuiting rings at both sides. The machine is started as a squirrel cage induction motor first. When it picks up speed, excitation is given to the rotor and the rotor starts rotating continuously as the rotor field is locked with stator revolving field. Thanks for watching this video. More about you learn to electrical engineering check out my videos Ohm's Law, and Kirchhoff's circuit laws. Don't forget like share and comment. More update please subscribes my channel Learning Engineering.

Contents

History

The first electric motor was invented in 1821 by Michael Faraday. The motor was developed only a year after Hans Christian Ørsted discovered that the flow of electric current creates a proportional magnetic field.[5] This early motor was simply a wire partially submerged into a glass of mercury with a magnet at the bottom. When the wire was connected to a battery a magnetic field was created and this interaction with the magnetic field given off by the magnet caused the wire to spin.

Ten years later the first electric generator was invented, again by Michael Faraday. This generator consisted of a magnet passing through a coil of wire and inducing current that was measured by a galvanometer. Faraday's research and experiments into electricity are the basis of most of modern electromechanical principles known today.[6]

Interest in electromechanics surged with the research into long distance communication.The Industrial Revolution's rapid increase in production gave rise to a demand for intracontinental communication, allowing electromechanics to make its way into public service. Relays originated with telegraphy as electromechanical devices were used to regenerate telegraph signals. The Strowger switch, the Panel switch, and similar devices were widely used in early automated telephone exchanges. Crossbar switches were first widely installed in the middle 20th century in Sweden, the United States, Canada, and Great Britain, and these quickly spread to the rest of the world.

Electromechanical systems saw a massive leap in progress from 1910-1945 as the world was put into global war twice. World War I saw a burst of new electromechanics as spotlights and radios were used by all countries.[7] By World War II, countries had developed and centralized their military around the versatility and power of electromechanics. One example of these still used today is the alternator, which was created to power military equipment in the 1950s and later repurposed for automobiles in the 1960s. Post-war America greatly benefited from the military's development of electromechanics as household work was quickly be replaced by electromechanical systems such as microwaves, refrigerators, and washing machines. The electromechanical television systems of the late 19th century were less successful.

Electric typewriters developed, up to the 1980s, as "power-assisted typewriters". They contained a single electrical component, the motor. Where the keystroke had previously moved a typebar directly, now it engaged mechanical linkages that directed mechanical power from the motor into the typebar. This was also true of the later IBM Selectric. At Bell Labs, in the 1946, the Bell Model V computer was developed. It was an electromechanical relay-based device; cycles took seconds. In 1968 electromechanical systems were still under serious consideration for an aircraft flight control computer, until a device based on large scale integration electronics was adopted in the Central Air Data Computer.

Modern practice

Today, electromechanical processes are mainly used by power companies. All fuel based generators convert mechanical movement to electrical power. Some renewable energies such as wind and hydroelectric are powered by mechanical systems that also convert movement to electricity.

In the last thirty years of the 20th century, equipment which would generally have used electromechanical devices became less expensive. This equipment became cheaper because it used more reliably integrated microcontroller circuits containing ultimately a few million transistors, and a program to carry out the same task through logic. With electromechanical components there were only moving parts, such as mechanical electric actuators. This more reliable logic has replaced most electromechanical devices, because any point in a system which must rely on mechanical movement for proper operation will inevitably have mechanical wear and eventually fail. Properly designed electronic circuits without moving parts will continue to operate correctly almost indefinitely and are used in most simple feedback control systems. Circuits without moving parts appear in a large number of items from traffic lights to washing machines.

Another electromechanical device is Piezoelectric devices, but they do not use electromagnetic principles. Piezoelectric devices can create sound or vibration from an electrical signal or create an electrical signal from sound or mechanical vibration.

To become an electromechanical engineer, typical college courses involve mathematics, engineering, computer science, designing of machines, and other automotive classes that help gain skill in troubleshooting and analyzing issues with machines. To be an electromechanical engineer a bachelor's degree is required, usually in electrical, mechanical, or electromechanical engineering. As of April 2018, only two universities, Michigan Technological University and Wentworth Institute of Technology, offer the major of electromechanical engineering. To enter the electromechanical field as an entry level technician, an associative degree is all that is required.

As of 2016, approximately 13,800 people work as electro-mechanical technicians in the US. The job outlook for 2016 to 2026 for technicians is 4% growth which is about an employment change of 500 positions. This outlook is slower than average.[8]

See also

Further reading

  • A first course in electromechanics. By Hugh Hildreth Skilling. Wiley, 1960.
  • Electromechanics: a first course in electromechanical energy conversion, Volume 1. By Hugh Hildreth Skilling. R. E. Krieger Pub. Co., Jan 1, 1979.
  • Electromechanics and electrical machinery. By J. F. Lindsay, M. H. Rashid. Prentice-Hall, 1986.
  • Electromechanical motion devices. By Hi-Dong Chai. Prentice Hall PTR, 1998.
  • Mechatronics: Electromechanics and Contromechanics. By Denny K. Miu. Springer London, Limited, 2011.

References and notes

Books and papers
  • Davim, J. Paulo, editor (2011) Mechatronics, John Wiley & Sons ISBN 978-1-84821-308-1 .
  • Furlani, Edward P. (August 15, 2001). Permanent Magnet and Electromechanical Devices: Materials, Analysis and Applications. Academic Press Series in Electromagnetism. San Diego: Academic Press. ISBN 0-12-269951-3. OCLC 47726317.
  • Krause, Paul C.; Wasynczuk, Oleg (1989). Electromechanical Motion Devices. McGraw-Hill Series in Electrical and Computer Engineering. New York: McGraw-Hill. ISBN 0-07-035494-4. OCLC 18224514.
  • Szolc T., Konowrocki R., Michajlow M., Pregowska A., An Investigation of the Dynamic Electromechanical Coupling Effects in Machine Drive Systems Driven by Asynchronous Motors, Mechanical Systems and Signal Processing, ISSN 0888-3270, Vol.49, pp. 118–134, 2014
  • "WWI: Technology and the weapons of war | NCpedia". www.ncpedia.org. Retrieved 2018-04-22.
Citations
  1. ^ Course in Electro-mechanics, for Students in Electrical Engineering, 1st Term of 3d Year, Columbia University, Adapted from Prof. F.E. Nipher's "Electricity and Magnetism". By Fitzhugh Townsend. 1901.
  2. ^ Szolc T.,; Konowrocki R.,; Michajłow M.,; Pregowska A., (2014). "An investigation of the dynamic electromechanical coupling effects in machine drive systems driven by asynchronous motors". Mechanical Systems and Signal Processing, Vol.49, pp.118-134. doi:10.1016/j.ymssp.2014.04.004. ISSN 0888-3270.
  3. ^ The Elements of Electricity, "Part V. Electro-Mechanics." By Wirt Robinson. John Wiley & sons, Incorporated, 1922.
  4. ^ Konowrocki R.,; Szolc T.,; Pochanke A.,; Pregowska A., (2016). "An influence of the stepping motor control and friction models on precise positioning of the complex mechanical system". Mechanical Systems and Signal Processing. Mechanical Systems and Signal Processing, Vol.70-71, pp.397-413. 70-71: 397–413. doi:10.1016/j.ymssp.2015.09.030. ISSN 0888-3270.
  5. ^ "Michael Faraday's electric magnetic rotation apparatus (motor)". Retrieved 2018-04-14.
  6. ^ "Michael Faraday's generator". Retrieved 2018-04-14.
  7. ^ "WWI: Technology and the weapons of war | NCpedia". www.ncpedia.org. Retrieved 2018-04-22.
  8. ^ Bureau of Labor Statistics, U.S. Department of Labor, Occupational Outlook Handbook, Electro-mechanical Technicians, on the Internet at http://www.bls.gov/ooh/architecture-and-engineering/electro-mechanical-technicians.htm (visited April 13, 2018).
This page was last edited on 4 October 2018, at 23:53
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