The Diagnostics of the rotor misalignment of a permanent magnet motor

A mathematical model of the magnetic field in the working gap of a brushless motor is considered in a case of rotor misalignment arising during manufacture, for example, due to defects in end shields, or in operation due to bearing wear. a gap in a uniform (circular ring). The stator gearing is taken into account on average using the Carter coefficient, the magnetic field in the inhomogeneous air gap, created by the rotor magnets and the stator winding current, is assumed to be plane-parallel, having a two-dimensional character. It was found that the rotor misalignment associated with the rotational movement of the eccentricity causes nonsinusoidality of the idle EMF and pulsation of the electromagnetic moment with a frequency 3p times higher than the rotor speed. When the eccentricity is stationary, a variable EMF is induced along the rotor shaft, causing an alternating current in the circuit: shaft-bearings-bearing shields-stator housing. To clarify the nature of the defect in order to identify the actual misalignment of the rotor, it is recommended to control currents and voltages using specialized software and hardware complexes for spectrum analysis.

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.

Establishing patterns in the compatible electromagnetic and electromechanical transition processes when the starter is powered by a supercapacitor

Supercapacitors are commonly used for a guaranteed launch of diesel generators. However, the processes caused by the starting current until the starter shaft rotates are disregarded. The duration of this moment is short but its effect on the rechargeable battery, taking into consideration its service life, is significant. The shape of this pulse, its duration significantly depend on the ratio of system parameters: supercapacitor (rechargeable battery) – starter – diesel generator. A system of differential equations has been proposed to describe the compatible electromagnetic and electromechanical processes that occur when the starter of the diesel generator is powered from the supercapacitor. A charge is used as a variable quantity. The transitional processes occurring in the stationary starter rotor and the subsequent processes caused by the growth of the electromagnetic starter moment have been taken into consideration. This paper reports establishing those patterns that are related to the beginning of the starter movement, its entering the mode at the falling voltage of the supercapacitor, the exchange of electrical and magnetic energy accumulated in the inductive elements of the starter. Using the charge as a variable quantity has made it possible to combine the final values of the preceding process (stationary rotor) with the initial ones of the next one (output to starting speed). Thus, a mathematical notation has been derived that considers most of the parameters of the charge circle of the supercapacitor. The possibility of using an inflated voltage of the supercapacitor to increase the accumulated energy has been clarified. The processes have been theoretically substantiated, which makes it possible to use a small internal resistance of the starter circuit, the presence of inductive components, an abnormal capacity of the supercapacitor to form the desired shape of the electromagnetic moment. That would make it possible to take into consideration the specific requirements of various systems of guaranteed power supply.

MAGNETO-ELECTRIC ENERGY CONVERTER OF SEA WAVES

To convert the energy of sea waves, the use of cylindrical (with a radial magnetic flux) three-phase magnetoelectric generators with a permanent magnet rotor using a mechanical gearbox to increase the rotor speed is considered. Given the real rotor motion, a mathematical model has been developed to calculate the distribution of magnetic fields in the gap of the generator, and functional dependences of the flux linkage of the winding and the electromagnetic moment of the generator on its design and the parameters of permanent magnets have been obtained. For the adopted design, the electromagnetic moment, the distribution of phase currents in the windings, the power and voltage of the generator are determined. A comparison is made of the energy performance of generators with a traditional float drive and using a ratchet to ensure one-sided rotation of the rotor. The expediency of using a ratchet generator to convert the energy of sea waves is considered. References 6, figures 7.

EXPERIMENTAL STUDY OF THE STATIC CHARACTERISTICS OF THE SYNCHRONOUS MACHINE IN THE MODE OF DYNAMIC BRAKING WITH INDUCTION RESISTANCE IN THE WINDING OF THE STATOR

The article discusses the results of a study of the static electromechanical characteristics of a synchronous machine (SM) when prototypes of induction resistances (IR) with improved parameters are included in its stator circuits. Widespread in practice, dynamic braking (DB) of synchronous machines provides for the dissipation of the kinetic energy of the rotor in the resistance boxes included in the stator winding. In the process of stopping, to maintain the constancy of the average braking torque of the SM, a bulky relay-contactor shunt circuit for stator resistances is used. At low speeds, regulation of the excitation current of the SM or its forcing can also be applied. However, it is not possible to eliminate significant fluctuations in the electromagnetic moment in this way. To optimize the SM DB process, instead of resistance boxes, it was proposed to include a three-phase induction resistance in the stator winding, the value of which automatically decreases along with the stator current frequency. This approach allows you to drastically reduce the number of contact equipment and ensure smooth braking of the machine with electromagnetic moment fluctuations within narrow limits. Known IR designs are designed for asynchronous motors with a phase rotor and satisfy the requirements of the given quality factor of their starting characteristics, but cannot ensure the constancy of the torque on the SM shaft in the DB mode. Therefore, the objective of the work is to improve the design of the IR and obtain the necessary inhibitory mechanical characteristics of the SM using experimental studies. The work provides a pilot plant diagram and a drawing explaining the design features of the IR. The studies were performed for a synchronous machine, type МСА-72 / 4А, equipped with a thyristor exciter and a speed sensor. In three phases of the SM stator, IRs connected by a "star" were turned on. The experiments were carried out in the direction of obtaining the necessary braking characteristics of the SM by varying the design of the internal elements of the IR. The figures show the mechanical characteristics of the SM obtained in the process of studying the effect on them of the thickness of the inner steel rings and massive ferromagnetic disks at three values of the fixed excitation current. The research results show that the desired form of the mentioned characteristics of the SM is achieved only when using massive internal elements in the design of the IR. A separate figure shows the curves of changes in some values of the SM load, which will facilitate the development of methods for calculating the DB mode of the machine for the optimal design of the IR.

INCREASE IN THE ELECTROMAGNETIC MOMENT OF A SUPERMINIATURE ELECTRIC MOTOR EXCITED BY RARE EARTH PERMANENT MAGNETS

The article is devoted to improving the energy and performance characteristics of superminiature electric motors, which are widely used in modern devices of robotics and mechanotronics. With the development of digital and Autonomous robotic systems, the tasks of improving the efficiency of Executive micromechanisms that affect the functionality and duration of work in offline mode have become particularly relevant. Traditional design and technological solutions used in higher-power electric machines are not scalable to the field of superminiature electric machines. Domestic and foreign developers offer various design options and manufacturing technologies. The key design feature of the electric motor under consideration is a glass stator made by polycapillary fiber technology and an excitation system from rare-earth permanent magnets. In the wall of the glass case, holes are evenly distributed around the circumference, in which the control winding is laid. The motor excitation system is a two-pole permanent magnet located on the rotating rotor shaft. The purpose of the research is to determine the effect of changing the design of the excitation system by changing the location of the magnetic poles. The research uses software that simulates the electromagnetic field using the finite element method. In the course of research, it was found that a decrease in the body of a permanent magnet leads to a decrease in the electromagnetic moment, which is not compensated by a decrease in edge effects at the boundary of the poles of the magnet. However, an increase in the value of the maximum magnetic induction in the air gap allows us to conclude that edge effects at the pole boundary have a significant effect on reducing the energy characteristics of superminiature micromachines. Thus, the solutions proposed in this paper are not sufficient to increase the efficiency of the engine, but the data obtained indicate the need to reduce the edge effects of permanent magnets.

MODEL OF AN ADJUSTABLE ELECTROMAGNETIC GEARBOX WITH A THREE-PHASE STATOR WINDING IN THE STATE SPACE

A magnetic gearbox with a three-phase stator winding, powered by a static frequency converter with a sinusoidal current, which is in phase or in antiphase with the EMF of the idling winding, will have in this mode the maximum values ​​of the electromagnetic moments of the shafts proportional to the stator current. Such a gearbox will have no “overturning” of the rotors as long as the frequency converter is able to increase its current with increasing load. The electromagnetic moments of the rotors of the magnetic gear are a consequence of the presence of the electromagnetic moment of the stator. The electromagnetic moments of the rotors are rigidly related to the electromagnetic moment of the stator through constant coefficients. A mathematical model of an adjustable magnetic gearbox with a three-phase stator winding and the results of modeling a dynamic system are presented. Offers the structure of the output shaft speed stabilization system, such as a wind turbine. The introduction of the main research results is illustrated.