The increase (more than four) of an AC inverter drive phase number is an effective method of improvement of most important characteristics of the above mentioned electromechanical system. For example, the increase of a phase number leads to the next effects (without any increase in complication degree of the inverter cont¬rol algorithm) [1-7]:

1) The increase in the frequency and the decrease in the value of an AC motor torque pulsation. This effect allows to increase a range of speed change.

2) The increase in the frequency and the decrease in the value of current pulsation in the input circuit of an inverter. This effect allows to decrease a value of a capacitance in the input circuit of an inverter.

3) The decrease of power losses in the rotor circuits of AC motors. This effect leads to an increase of the value of motor efficiency.

4) Opportunity of the use of some non-traditional motor control methods which allows to increase the control resources of the drive system, to increase the maximum and starting torques of the motor and to decrease the mass-and-overall dimensions of the AC motor which is used in the given electromechanical system.

5) The increase in the reliability parameters of the drive system (by the use of some specific methods of inverter control).

The making of the multiphase AC motors and inverters is not more difficult than the making of the 3-phase analogous devices and needs no change of the available production equipments.

REFERENCES:

1. A.V. Brazhnikov, and I.R. Belozerov, “Over-Phase Control of Inverter Multiphase AC Linear Drives”, Journal “Mechatronics”, Elsevier Publishing Company, vol. 23, issue 2, March 2013, pp. 227-232, DOI 10.1016/j.mechatronics.2012.02.003.

2. A.V. Brazhnikov, and E.S. Brazhnikova, “Novel Generation of Hybrid Traction Drives With AC Induction Motors for Railway Vehicles – Principles of Designing”, Proceedings of the 2012 International Session at Annual Conference & Meeting of the Korean Society for Railway “ISKSR ’2012”, GyeongJu, South Korea, October 18-20, 2012, reg. No R0043, pp. 44-49.

3. A.V. Brazhnikov, and I.R. Belozyorov, “Over-Phase Control of Inverter Multiphase AC Linear Drives”, Online Edition “Advances in Engineering”, Canada, July 2012.

4. A.V. Brazhnikov, E.S. Brazhnikova, and I.R. Belozerov, “PPM-Based Development-and-Control Strategy of Fault Tolerant Inverter-Fed Multiphase Electromechanical AC Systems”, Proceedings of 21st International Symposium on Power Electronics, Electrical Drives, Automation and Motion “SPEEDAM ‘2012”, Sorrento, Italy, June 20-22, 2012, paper No EMD0047, pp. 237-242.

5. A.V. Brazhnikov, and E.S. Brazhnikova, “Efficiency Invariance Laws and Development of Multiphase AC Inverter Drives”, Proceedings of 21st International Symposium on Power Electronics, Electrical Drives, Automation and Motion “SPEEDAM ‘2012”, Sorrento, Italy, June 20-22, 2012, paper No EMD0052, pp. 420-425.

6. A.V. Brazhnikov, and I.R. Belozerov, “Space-Temporal Spectral Relations and Energy Efficiency Invariance Laws Acting in the Field of Inverter-Fed Multiphase AC Drives”, Proceedings of IET 6th International Conference on Power Electronics, Machines and Drives “PEMD ‘2012”, Bristol, the United Kingdom, March 27-29, 2012, paper No 0027, vol. 2, p. 1094-1099.

7. A.V. Brazhnikov, and I.R. Belozerov, “Prospects for the Use of Multiphase Inverter-Fed Asynchronous Drives in the Field of Traction Systems of Railway Vehicles”, Journal “International Journal of Railway” (IJR, South Korea), Vol. 5, No 1, March 2012, pp. 38-47.