July 4th

Extreme possibilities of circuital models of electrical machines

The paper presents possibilities of so-called circuital mathematical models of electric machines, in which the machine is treated as a set of magnetically coupled coils. It is a very popular class of models used for analysis of operational conditions of electric machines. However, the progress in numerical solutions of electromagnetic filed causes the interest of researchers to shift into so-called field-models.

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July 3rd

A 50 km/h snail for city use

If you live in or visit some of the megacities with transportation problems you surely find yourself envying the motorcyclists. Cruising between the cars, even without travelling at high speeds, they are reaching their destination well ahead of those of us in cars. Here is the ultimate solution: a solar powered motorcycle energy storage capacity for 20km and a top-speed of 50 km/h!

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Rotor power loss in a PM SM by calculation, simulation and measurements, mutual verification of methods

The subject of the paper is the comparison of four complementary methods of the rotor loss estimation in a PM SM, supplied by a PWM voltage source. An ANSYS based finite element model produces values of W, the magnetic energy stored, and P, the rotor losses. On analytical level the machine is represented by a parallel two elements equivalent circuit for each voltage harmonic. Its parameters are estimated using P and W values.

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July 2nd

The world in 2050

Projections according to Shell

In their "Sustainability Report 2006" Shell gives a few key figures to paint a picture of the world in 2050 and to compare it with the world we are living in today, and the world as it was in 1907, when Shell was founded.

In 2050 the world will

  • be inhabited by 9 billion people, compared to 6.5 billion today and 1.7 billion back in 1907
  • be 4 to 5 times richer, with most of the wealth coming from rapidly industrialising developing countries
  • use twice as much energy as today and 25 times as much as in 1907
  • be twice as energy efficient as today, using half as much energy to produce each dollar of wealth
  • use 6 to 10 times more energy from renewable sources like wind, solar, hydro, and biofuels.
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Additional losses by magnetic field harmonics in the rotor bars of asynchronous machines and their influence

Optimizing the efficiency of modern asynchronous machines requires the knowledge of the particular loss components. In this contribution a method shall be presented, where by the transient FEM-calculation the copper losses in the rotor bars by harmonic field effects and the consequential originating harmonic currents can be estimated. By this way the determination of the current density of the rotor current harmonics is carried out along the height of the rotor bar.

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July 1st

Electromagnetically excited audible noise - evaluation and optimisation of electrical machines by numerical simulation

Disturbing vibrations and noise of electrical machines are gaining impact. Therefore, it is necessary to estimate the electromagnetic, structure-dynamical, and acoustic behavior of the machine during designing and before prototyping. An adequate tool is numerical simulation applying the Finite-Element Method (FEM) and the Boundary-Element Method (BEM) allowing for the structured analysis and evaluation of audible noise also caused by manufacturing tolerances.

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