Winding coefficient and rotor losses in servo motors with stator tooth concentrated windings

Аuthors

Sen'kov A. P.^1*, Bormotov A. V.^2**, Sedunov D. Y.^3***

1. State Marine Technical University of St. Petersburg, MTU, 3, Lotsmanskaya str., St. Petersburg, 190008, Russia
2. Diakont, 2, Uchitelskaja str., St. Petersburg, 195274, Russia
3. ITMO University, 49, Kronverkskiy av , St. Petersburg, 197101, Russia

*e-mail: senkov@smtu.ru
**e-mail: bormotov@diakont.com
***e-mail: sedunov@diakont.com

Abstract

The article describes methods of winding ratio determining in AC electric motors with tooth stator coils and permanent magnets rotor, and presents the values for several design styles of such motors.

On the example of the three-phase two-piece electric motor with radial flux, 18 teeth of the stator and 10 rotor poles, an analytical expression of the winding ratio was obtained (from the slot e. m. f. first harmonics vector diagram and the instantaneous rotor position). Additionally, alternative analytical method for determining the winding ratio is shown (based on the known expressions for the motors with distributed two- layer stator winding with adaptation to the tooth winding motors).

As the result of this calculation it we concluded that the value of the winding factor increases with the number of coils in the coil phase group.

The paper presents a comparative analysis of the electric motors of distributed and tooth stator windings design, highlights a number of positive features of tooth windings motors. We made a hypothesis on eddy currents origin in rotor elements due to the presence of pulsating electromagnetic stator flux. Distribution nature and eddy current losses value that occur in the rotor and its elements (for three different speeds) are shown with the motor model in Ansys Maxwell v.16. package finite element analysis.

As one of electric motor efficiency factors, the value of winding coefficient (obtained for a particular number combination of the rotor pole pairs and stator teeth) allowed choose the most efficient motor in electromechanical actuator design stage. Knowledge of eddy current value and distribution nature in the rotor design elements allowed take measures, leading to these losses reducion.

The article is prepared in accordance with R&D work High-tech production creation of precision high- speed enforced electromechanical actuators of the new generation at ITMO Univercity, with financial support from Russian Federation Ministry of Education and Science.

Keywords:

PMSM, tooth pitch, winding factor, losses, simulation, actuator

References

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