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Chapter 3: Electromechanical-Energy-Conversion


This lecture note is based on the textbook # 1. Electric Machinery - A.E. Fitzgerald, Charles Kingsley, Jr., Stephen D. Umans- 6th edition- Mc Graw Hill series in Electrical Engineering. Power and Energy

  • The electromechanical-energy-conversion process takes place through the medium of the electric or magnetic field of the conversion device of which the structures depend on their respective functions.
  • Transducers: microphone, pickup, sensor, loudspeaker
  • Force producing devices: solenoid, relay, electromagnet
  • Continuous energy conversion equipment: motor, generator

This chapter is devoted to the principles of electromechanical energy conversion and the analysis of the devices accomplishing this function. Emphasis is placed on the analysis of systems that use magnetic fields as the conversion medium.

  • The concepts and techniques can be applied to a wide range of engineering situations involving electromechanical energy conversion.
  • Based on the energy method, we are to develop expressions for forces and torques in magnetic-field-based electromechanical systems.

§3.1 Forces and Torques in Magnetic Field Systems

  • The Lorentz Force Law gives the force F on a particle of charge q in the presence of electric and magnetic fields.

F = q ( E + v × B ) size 12{F=q \( E+v times B \) } {} (3.1)

F : newtons, q : coulombs, E : volts/meter, B : telsas, v : meters/second

  • In a pure electric-field system,

F  qE (3.2)

  • In pure magnetic-field systems,

F = q ( v × B ) size 12{F=q \( v times B \) } {} (3.3)

Figure 3.1 Right-hand rule for F=( q x v) B .

  • For situations where large numbers of charged particles are in motion,

F v = ρ ( E + v × B ) size 12{F rSub { size 8{v} } =ρ \( E+v times B \) } {} (3.4)

J = ρv size 12{J=ρv} {} (3.5)

F v = J × B size 12{F rSub { size 8{v} } =J times B} {} (3.6)

 (charge density): coulombs/ m 3 size 12{m rSup { size 8{3} } } {} , F (force density): newtons/ m 3 size 12{m rSup { size 8{3} } } {} ,

J = ρv size 12{J=ρv} {} (current density): amperes/ m 2 size 12{m rSup { size 8{2} } } {} .

  • Most electromechanical-energy-conversion devices contain magnetic material.
  • Forces act directly on the magnetic material of these devices which are constructed of rigid, nondeforming structures.
  • The performance of these devices is typically determined by the net force, or torque, acting on the moving component. It is rarely necessary to calculate the details of the internal force distribution.
  • Just as a compass needle tries to align with the earth’s magnetic field, the two sets of fields associated with the rotor and the stator of rotating machinery attempt to align, and torque is associated with their displacement from alignment.
    • In a motor, the stator magnetic field rotates ahead of that of the rotor, pulling on it and performing work.
    • For a generator, the rotor does the work on the stator.
      • The Energy Method
  • Based on the principle of conservation of energy: energy is neither created nor destroyed; it is merely changed in form.
  • Fig. 3.2(a): a magnetic-field-based electromechanical-energy-conversion device.
    • A lossless magnetic-energy-storage system with two terminals
    • The electric terminal has two terminal variables: e (voltage), i (current).
    • The mechanical terminal has two terminal variables: f fld size 12{f rSub { size 8{ ital "fld"} } } {} (force), x (position)
    • The loss mechanism is separated from the energy-storage mechanism.

Questions & Answers

what is Nano technology ?
Bob Reply
write examples of Nano molecule?
The nanotechnology is as new science, to scale nanometric
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
what school?
biomolecules are e building blocks of every organics and inorganic materials.
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
sciencedirect big data base
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
characteristics of micro business
for teaching engĺish at school how nano technology help us
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
what is the actual application of fullerenes nowadays?
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
is Bucky paper clear?
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Do you know which machine is used to that process?
how to fabricate graphene ink ?
for screen printed electrodes ?
What is lattice structure?
s. Reply
of graphene you mean?
or in general
in general
Graphene has a hexagonal structure
On having this app for quite a bit time, Haven't realised there's a chat room in it.
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Intergrated library system management. OpenStax CNX. Jul 29, 2009 Download for free at http://cnx.org/content/col10801/1.1
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