Year of grant:
Novel Geometri Induction Motor with Improved Efficiency.
Bogi Bech Jensen
University of Newcastle upon Tyne, UK
1.9.2006 - 31.8.2009
Final: 0.092006 - 01.12.2009
Grant from the FRC in DKK:
It is clear that energy is a crucial issue for the world’s future. In developed countries more than 60% of generated electrical energy is used on motors, and about 80% of that is used on induction motors. These motors are currently constraint by the need to start directly from the grid supply (DOL). This constraint results in a reduced efficiency due to the necessary presence of a relatively large rotor resistance.
The mentioned constraints in induction motor design are not present if power electronic converters using field orientation (vector control) are employed. Power electronic converters are reducing in price year on year, and it is clear that if power electronics is used a radical redesign of current induction machine design and construction is possible. This will allow a large increase in efficiency of the motor from typically 70%, for a machine in the low kW range, to as high as 85% for the power electronically driven version.
To achieve this change completely new design and construction is needed. Specifically non-overlapped coils can drastically reduce losses in the winding (the dominant loss). However, these need completely new methods of construction to make them possible and careful control of harmonics via changes in the design. Formerly these changes would have resulted in the phenomenon known as asynchronous crawling. This latter is completely avoided using power electronics hence the research opportunity.
As the induction motor is used so extensively and the efficiency could be raised so significantly such improvements, if successfully commercialised, could revolutionise the global industry, especially any kind of production which typically employs vast amounts of variable speed induction motors.
Small and medium size induction machines typically employ overlapped concentrically would stator windings. This work presents the development, design, construction and testing of a toroidally would induction machine. The rotor is a standard squirrel-cage rotor except that it has been adjusted according to the stator design. The toroidal windings do not overlap and hence are tightly wound around the core, which leads to superior thermal performance as compared to the conventionally would machines. Non-overlapped tooth would coils commonly used in permanent magnet machines would produce unacceptable harmonics in an induction machine. However, this work shows that toroidally would coils do not give rise to any problems due to harmonics.
Jensen, B.B., A. G. Jack, ”Performance of a Folded-Strip Toroidally Wound Induction Machine”, written for submission to IEEE Transactions on Energy Conversion.
Jensen, B. B., “Estimating the Reactive Parameters of an Induction Machine using Static 2D Finite Element Modelling”, submitted to Electric Power Components and Systems, Taylor and Francis.
Jensen, B. B., Jack, A. G., ”Toroidally Wound Induction Machines”, submitted to ICEM 2010, 19th International Conference on Electical Machines, Rome, Italy, 2010.