Theory of Electrical Machines

This course is offered in German.

Learning objective:

The module deepens the basic knowledge of synchronous and induction machines with specific insights into their design and the causes of undesirable parasitic effects such as additional losses, acoustic noise emissions and vibration excitations. Students learn to independently analyze practically relevant noise and vibration problems and to assess whether and through which measures disturbing side effects can be reduced or avoided. They also learn how to design synchronous and induction machines to meet requirements.

Contents:

• Synchronous machines: Construction and cooling methods of synchronous machines.
• Operating behavior of salient pole synchronous machines in steady state: phasor diagram, equivalent circuit diagram, current locus, voltage equations, Potier triangles, permanent magnet synchronous motors, synchronous reluctance motors.
• Unbalanced load on synchronous generators.
• Introduction to the spatial harmonic theory (representation of the electric loading and field excitation curve as infinite Fourier series of the spatial waves), harmonic leakage, skewing.
• Electromagnetic design
• Theory of windings: design rules and calculation of winding factors for integral-slot and fractional-slot windings, interspersed windings, pole-changing windings, Görges diagrams for determining the field excitation curve and the coefficient of harmonic leakage.
• Parametric fields due to variations of the magnetic conductance (e.g. saturation, eccentricity and slot-harmonic fields)
• Theory of current displacement in cage windings
• Field damping by cage and slip-ring rotors
• Field damping due to parallel winding branches of phase windings
• Tangential mechanical forces (general calculation, asynchronous and synchronous spatial harmonic torques)
• Radial mechanical forces (generation of magnetically excited acoustic noise and mechanical vibrations, unbalanced magnetic pull and its influence on the lateral critical speed of the shaft)
• Loss mechanisms, additional losses due to spatial harmonics

Previous Knowledge:

Principles of electromagnetic power conversion