SU907713A1 - Magnetoelectric synchronous generator of reverse structure - Google Patents

Description

(54) MAGNETOELECTRIC SYNCHRONOUS GENERATOR OF REVERSED CONSTRUCTION

one

The invention relates to electric machines driven by permanent magnets, and can be used in synchronous generators to stabilize the voltage at a variable rotor speed, in DC valve generators, and-or in generators of a frequency-output generator system (variable speed — constant frequency) driven by a turbine whose rotational frequency is not constant, for example, an aircraft turbine.

A known magnetoelectric synchronous generator, in which voltage stabilization is carried out by biasing the magnetic circuit. It has a winding, bias, which acts on the magnetic circuit of the generator on command from the sensitive element, which records the voltage deviation from the specified 1.

However, the additional winding and control equipment increases the weight and size, and also complicates the design.

The known structure of the rotor is a synchronous mask, in which the movement of permanent magnets is used in order to improve the starting characteristics in the motor

mode. On the rotor of such a mask, next to the starting winding, there is located on a helical gear an asterisk made of permanent magnets, which, when the rotor accelerates, moves in the axial direction due to the action of inertial forces and can take a different position relative to the stator bore 2.

A disadvantage of the known construction is the poor use of active materials, since in synchronous mode

10, the part of the active length of the machine, to which the starting winding of the rotor falls, does not participate in the creation of the electromagnetic moment. When starting the engine, there is a similar drawback, since the starting winding takes only a part of the active length of the machine.

The closest in technical essence to the invention is a magnetoelectric synchronous generator of a reversed structure, which contains prism permanent magnets uniformly circumferentially on the rotor so that their poles of the same name are adjacent, ferromagnetic poles located in the gaps

between prismatic permanent magnets, means of stirring, yen part of the rotor magnetic circuit under the action of centrifugal forces and a damping device.

By virtue of the principle of reversibility of electric machines, such a synchronous machine can be used in generator mode 3.

The disadvantage is that the magnets only move in the radial direction and the non-magnetic gap between the rotor and the stator does not change, and to stabilize the voltage when the rotational frequency changes, a significant movement of the magnets will be required. For example, if the rotational speed changes twice as compared to the nominal one, the magnets will need to be moved half the active machine length (at the end). The centrifugal force acting on the magnet must be balanced by the elastic force of the spring. With the increased rotational frequencies of rotors for aircraft electric machines, the centrifugal force will exceed hundreds and thousands of times. The weight and elastic elements of the rotor must withstand enormous mechanical loads, which excludes the possibility of practical implementation of a generator with a rotor of a similar design.

In addition, in the rotor there is no consistent movement of all the magnets. Due to a number of reasons (different friction and weight of individual magnets, different elasticity of springs, etc.), various magnets will move for different distances, which will lead to an imbalance of the rotor and its destruction. Machines with end stators and rotors are characterized by significant axial magnetic pull forces, which significantly complicates the operation of bearing assemblies.

The purpose of the invention is to increase the reliability of stabilizing the generator voltage at a variable rotation frequency of the rotor.

This goal is achieved by the fact that the devices for moving a part of the rotor are made in the form of a disk, a non-magnetic shell rigidly connected to it, the inner surface of which is inclined, connected with the moving frequencies of the rotor and rigidly connected to the fixed parts of the rotor, and a non-magnetic ring fixed on the end surfaces of all moving parts of the rotor, and the damping device is made in the form of a spring-loaded ring placed between the disk and the non-magnetic ring.

Moreover, the permanent magnets can be rigidly fixed in a C-shaped non-magnetic bracket having an external surface with an inclination angle equal to the angle of inclination of the shell and installed in the latter, and the ferromagnetic poles are rigidly connected to the shell.

In addition, the permanent magnets are rigidly connected to the shell.

FIG. 1 shows a rotor with one-sided displacement of its part, a longitudinal section; in fig. 2 - the same, bilateral displacement of its part; in fig. 3 - rotor with movable magnets, cross section; in fig. 4 - decomposition of centrifugal force; in fig. 5 is a graphical method for calculating the elastic force of a rotor damping device.

In the magnetoelectric synchronous generator of the reversed structure, the rotor is located in the radome of the aircraft engine head section (Fig. 1). The relatively short outer rotor of the generator is fixed with KOHCoj bHo on the shaft of the aircraft engine, and the stator with the core winding is located inside the rotor and is attached to the fairing. In such a generator, there are no bearing shields, a housing, a non-required gearbox, a special rotor release, etc.

The rotor consists of prismatic permanent magnets 1 having a large coercive force, for example, rare-earth magnets of the SmCOg type. Magnets are covered from the outer surface and the ends with C-shaped non-magnetic brackets 2. Brackets 2 together with magnets 1 are inserted into the grooves of the conical non-magnetic shell 3. The outer surfaces of the brackets 2 and the bottom of the grooves of the shell 3 have the same inclination with respect to the longitudinal axis of the rotor. Ferromagnetic poles 4, rigidly attached to shell 3, are located between adjacent magnets. The thickness of the magnets 1 and brackets 2 and the width of the slots in the shell 3 and between the poles 4 are chosen so that the magnets can slide along the slots. All brackets are interconnected by a non-magnetic ring 5 in such a way that they can move in the radial-axial direction only together.

A resilient, pre-compressed element 6, for example an annular bellows, a disc spring, etc., is placed between the ring 5 and the disk part of the rotor 7. Between the poles 4- a wedge 8 is installed on the inner surface of the rotor.

The elastic element b can be installed on the right (Fig. 1) and then it works in compression, as well as on the left (the elastic element will stretch).

FIG. Figure 2 shows a rotor in which only the extreme magnets can move in different directions, and the central one remains in place. The rotor design can be made with fixed magnets and movable ferromagnetic poles. The choice of the moving parts of the rotor (magnetic tubes 1 or poles 4) and the method of installation of the elastic element 6 are determined by the specific conditions of operation of the generator.

The generator voltage is stabilized by varying the rotor speed η as follows.

When n deviates from the nominal, the moving parts of the rotor move in the radial-axial direction under the action of the axial force F (. (Fig. 4). If the rotor speed increases, n, the FC increases, the elastic element 6 is pressed and the moving part of the rotor moves to the right by a distance D Z, whereby the excitation flux Φ decreases. When the rotor rotates at a reduced frequency n, the force 1. decreases and the elastic element 6 by moving the movable rotor part to the left increases the excitation flux. it is the dC contact surfaces of the moving parts of the rotor and shell 3 and the rigidity of the elastic element 6 can achieve the necessary connection between the increment of the rotor rotation frequency n and the excitation flow increment f, at which the generator voltage will be constant throughout the calculated range of n change (even taking into account the influence of f p on the inductive resistance of the core). The change of the excitation flux F as the magnets move in the radial-axial direction occurs as due to the change in the length of the magnets within the bore of the as well as by varying the scattering pole in between, the liberated (occupied by the) magnets. The change in the excitation flux Φ in the case of moving poles occurs due to a change in the nonmagnetic gap and the active length. One of the possible ways to select the angle of inclination of. The supporting surfaces of the movable magnets and the stiffness of the elastic element are illustrated graphically in FIG. five.

In quadrant II, the force 1, compressing the elastic element 6, is plotted against the angular frequency of the rotation of the rotor

FO ma) 2Rsinodcoso (. 0,5mK.cJ faf sm2oL where S is the nominal rotation frequency;

m is the mass of magnets with brackets;

 ul

 - relative frequency of rotation; R const radius of the center of the rotating mass

magnets.

Quadrant IV presents the dependence of the flux pole f on the axial displacement of the pole magnet, which can be obtained by calculation or experimentally. In the first quadrant, the magnetic field strength F. f (AZ), the elastic force of the bellows Fy f (AZ) are plotted against the magnitude of the movement of the rotor parts and the total axial force FF + FM, which balances the axial force ff .. The force F ,, is due to the magnetic the flow that occurs between the ends of the poles 4 and the parts of the permanent magnets that are extruded beyond their limits. It prevents the magnets from escaping the interpolar grooves and increases with increasing magnitude of movement of the rotor parts D Z up to a certain limit. Dependence 1 f (AZ) can be determined by calculation

or experimentally. Based on the dependencies F. f (a3) and Ф f (AZ), taking into account 1 graphically, the dependence of the total counterbalancing force F f (AZ) is determined, after which the function Fy f (L Z) FF - I is determined graphically. the pressing of the elastic element is determined by using the function FC fCw) for the minimum speed cJt at which it is still possible to provide OZ, XX С}, - 1 at А Z 0. The calculation can also be carried out for moving poles in a similar way.

The proposed rotor does not provide voltage stabilization when the generator load changes. However, in a magnetoelectric generator, the synchronous resistance Xj is significantly smaller compared to generators with electromagnetic excitation and the voltage drop in it is smaller.

Claims (3)

1. A magnetoelectric synchronous generator of a reversed design, the rotor of which contains prismatic permanent magnets evenly spaced around the circumference and oriented by poles one more to the other, ferromagnetic poles located in the intervals between the permanent magnets, devices for moving parts of the rotor and a damping device differing from that, in order to increase the reliability of the generator voltage stabilization when the rotation frequency and the rotor change, the device for moving the rotor part are in the form of a disk, a non-magnetic shell rigidly connected to it, the inner surface of which is made inclined, is coupled with moving parts of the rotor and rigidly connected to the fixed parts of the rotor, and a non-magnetic ring fixed on the end surfaces of all moving parts of the rotor, and damping The device is made in the form of a spring-loaded ring placed between the disk and the non-magnetic ring. 2. The generator according to claim 1, characterized in that the permanent magnets are rigidly fixed in a C-shaped non-magnetic bracket having an external surface with an angle of inclination equal to the angle of inclination of the shell and installed in the latter, and the ferromagnetic poles are rigidly connected to the shell. 3. Generator according to claim 1, characterized in that the permanent magnets are rigidly connected to the shell. Sources of information taken into account in the examination 1. US patent number 3214675, cl. 322-46. 2. USSR author's certificate number 453773, cl. H 02 K 21/46, 1973. 3. USSR author's certificate number 527803, cl. H 02 K 21/46, 1974.