Voltage stabilization of a controlled autonomous magnetoelectric generator with a magnetic shunt and permanent magnet excitation

The paper presents the results of testing and research of the characteristics of a controlled autonomous magnetoelectric synchronous generator with a magnetic shunt. Structurally, the studied generator is a modified asynchronous machine in which the rotor is made with permanent magnets and an additional system in the form of a magnetic shunt. By adjusting the winding current of the magnetic shunt, the output voltage of the generator is regulated. The following characteristics were investigated: the no-load characteristic during operation with permanent magnets and when the winding current of the magnetic shunt changes with forward and reverse polarity. Also, the external characteristic for active and active-inductive loads; the control characteristic when the load current changes at a constant generator voltage. Analysis of the obtained characteristics makes it possible to determine the limits of regulation of the external characteristic, which is ≈40 % relative to the main magnetic flux. The obtained regulation depth allows maintaining the stability of the external characteristic for power factors not exceeding 0.9, which is the usual passport value for autonomous power plants based on synchronous generators. Comparison of the data of research conducted on the experimental setup shows sufficient convergence for engineering and practical tasks. The maximum quantitative difference is 9.3 %, which suggests the adequacy of the previously developed mathematical model. The control characteristic, constructed experimentally at constant generator voltage, is the control law of the magnetic shunt winding for the studied generator. The investigated version of a synchronous generator with a magnetic shunt should be used for autonomous power plants, renewable energy systems, and autonomous power supply systems.

Determining the effect of stator groove geometry in a traction synchronous reluctance motor with permanent magnets on the saw-shaped electromagnetic moment level

This paper reports the model of a magnetic field of the synchronous reluctance motor with permanent magnets that was developed on the basis of a finite-element method. The model was implemented in the FEMM finite-element analysis programming environment involving the application of the Lua-based script. The model makes it possible to determine the dependence of the engine's electromagnetic moment on the rotor rotation angle. Determining the level of a saw-shaped moment is important for assessing its harmful effect on the structural elements of the traction motor and the drive in general. The results of digital modeling have established the dependences of the electromagnetic moment on the rotor rotation angle. The moment has a variable component – the saw-shaped moment, whose amplitude for open grooves under a rated load mode is 182 Nm, and for semi-open grooves ‒ 90 Nm. The use of semi-open grooves exerts a positive effect on eliminating the saw-shaped moment in a synchronous reluctance motor with permanent magnets and may be recommended for further application on engines of this type. Semi-open grooves reduce the opening of the stator groove by 2 times and lead to a smoother flux distribution under the gear division. That reduces the oscillations of the main magnetic flux. The proposed application of semi-open stator grooves makes it possible to reduce by more than 2 times the level of a saw-shaped moment of the synchronous reluctance motor with permanent magnets under a rated mode. It has been determined that a rather positive factor is an increase of 4.8 % in the average motor moment value under a rated mode when using semi-open grooves. This is due to a decrease in the average value of magnetic resistance to the main magnetic flux. Therefore, with a simultaneous decrease in the moment's fluctuations, the transition to semi-open grooves makes it possible to improve the mass-dimensional indicators of the motor in general.