Specific parameters comparison of synchronous reluctance electric drives
The article presents the principles of comparison of different types of synchronous contactless electric drives. The mathematical description of the system is given for comparison. It is shown that classical unregulated synchronous electric drives are inferior to induction electric drives by 30–40%. It is caused by both a decrease in excitation and a decrease in the limiting load angle according to the conditions of static stability. The phase current of electric drives with FRRM has a rectangular shape which allows one to significantly improve the weight and dimensions. In this case, the electric drive with FRRM due to the compensation of the armature transverse response allows improving the system characteristics, so that the induction motor is 10–15% less than the FRRM.
On application of fractional single-toothed concentrated windings in synchronous machines with permanent magnets
Some properties of fractional single-toothed concentrated windings that contribute to their effective application in electrical machines have been considered. Small end windings allow making an electrical machine more compact in the axial direction, which makes it possible to use it in several applications: in motor-wheel drives, in a wind wheel power generator, in an elevator drive without room for a machine, etc. Fractional windings can significantly reduce the cogging torque of an electrical machine. This reduces the cogging torque, which is very important in wind energy, but at the same time it increases the smoothness and accuracy of positioning, which allows it to be used in special electrical machines. One of the drawbacks of the fractional single-toothed concentrated windings is a worse MMF harmonic content. With this in mind, application of a two-layer winding is to be preferred to that of a single-layer one. An example shows application of a fractional tooth concentrated winding in a synchronous engine with permanent magnets to drive the plunger pump used for oil production. The use of a two-layer winding instead of a single-layer one allowed reducing the eddy-current losses in the rotor by 3.7 times and avoiding unacceptable overheating of magnets.
Specifics of power circuit arrangements of semiconductor converters for power supply to synchronous reluctance machines
Power circuit arrangements of independently excited reactive electric drives are presented. It is shown that the number of switches is determined by the number of phases and lies in the range from 2f to 4f. It has been ascertained by regression analysis that the unit price of semiconductor converters at minor current values does not depend on current and is determined by the cost of the microprocessor control system. At currents >100 A, the price-current relation is nearly linear and the rejection of three-phase power circuits of semiconductor converters in favor of multiphase power circuits does not therefore increase power supply weight and size. Thus, the more complex configuration of power circuit arrangements (increased number of phases) for processing plants with an installed capacity of more than 200 kW can improve the weight and size of the electromechanical converter while maintaining the size of the semiconductor converter.