FR3061820A1 - ASYNCHRONOUS ELECTRIC MOTOR WITH RINGS - Google Patents

Abstract

An asynchronous electric ring motor comprising, for each phase, a variable resistance for starting assistance constituted by an electrolyte in which are placed two electrodes (13, 14), at least one of which is mobile, characterized in that each of the electrodes (13, 14) comprises raised elements (15, 16; 17, 18) of triangular section.

Description

Holder (s):

KOHEN ALBERT.

Agent (s): trusted.

IPSILON simpli® joint-stock company ASYNCHRONOUS RING ELECTRIC MOTOR.

@) Asynchronous electric motor with rings comprising at the rotor, for each phase, a variable resistance of assistance with starting constituted by an electrolyte in which are placed two electrodes (13, 14), of which at least one (14) is mobile , characterized in that each of the electrodes (13,14) comprises elements in relief (15,16; 17, 18) of triangular section.

FR 3,061,820 - A1

"Asynchronous electric motor with rings"

DOM N NE OF I NVENTI ON

The invention relates to an asynchronous electric motor with rings, particularly usable in the mining or cement industry. This industry uses, in particular for ball mills, motors of high power (several MW). To ensure their start-up, these motors require the insertion of a three-phase resistor on the rotor. The initial value of this resistance determines the starting torque. The start-up sequence lasts a few tens of seconds during which the rotor resistance is gradually reduced to a final value close to zero, before being short-circuited.

ANTERIOR ART EUR

US Patent 2,719,256 describes a device for controlling the starting of an asynchronous electric ring motor for the mining industry, with, between the rotor and the ground, variable resistances. For each phase of the rotor, the variable resistance is constituted by an electrolyte placed in a vertical cylinder, between a fixed electrode at the bottom of the cylinder, and a mobile electrode. The movable electrode is moved between an initial position at the top of the cylinder and a final position at the bottom of the cylinder, near the fixed electrode. In this document, the electrodes are constituted by substantially identical discs. The resistance R between the electrodes is approximated by the formula:

R = p.d / S

P is the resistivity of the electrolyte, of the distance between the electrodes and S the surface opposite the electrodes. To start the engine, the initial resistance Ri must be large, and the mobile electrode is placed at the top of the cylinder. At the end of starting, the resistance Rf must be as low as possible and the mobile electrode is brought closer to the fixed electrode, at the bottom of the cylinder. To improve the Ri / Rf ratio, the manufacturers used not only the variation of d, but also the variation of S. For this purpose, the fixed and mobile electrodes were each constructed in the form of coaxial cylinders. Thus, at the end of the descent of the mobile electrode, the cylinders of the mobile electrode are inserted between the cylinders of the fixed electrode and the surface S to be taken into account for the evaluation of the final resistance Rf is the surface next to the electrodes. In this embodiment, where the final distance between the cylinders of the two electrodes is approximately 15 mm, the value of the ratio Ri / Rf can hardly reach the value of 100.

GOALS AND SUMMARY

An object of the invention is to provide an asynchronous electric motor with rings for the mining industry, equipped with variable electrolyte resistors, having a Ri / Rf ratio significantly greater than 100.

Another object of the invention is to propose an asynchronous electric motor with rings for the mining industry, equipped with variable electrolyte resistors, comprising arrangements for increasing the value of the ratio Ri / Rf and the operational safety of the control device. engine start.

The subject of the invention is an asynchronous electric motor with rings comprising at the rotor, for each phase, a variable resistance for assistance in starting consisting of an electrolyte in which two electrodes are placed, at least one of which is mobile, characterized in that each of the electrodes comprises elements in relief of triangular section.

Preferably, the triangular section of the elements in relief is an isosceles triangle whose angle at the apex is between 3 and 15 °.

Advantageously, the elements in relief of the electrodes have interpenetrating shapes.

According to one embodiment, the elements in relief of the electrodes are prisms.

According to one embodiment, the elements in relief of the electrodes are coaxial rings.

Advantageously, the radii of the coaxial rings of each electrode differ by a constant pitch.

Advantageously, the radii of the coaxial rings of the movable electrode differ from the radii of the coaxial rings of the fixed electrode by half a step.

According to one embodiment, the fixed and mobile electrodes are placed in a cylindrical insulating tank with a diameter close to that of the electrodes.

Preferably, the insulating tank is vertical, the fixed electrode is at the bottom of the insulating tank and the mobile electrode is moved in the insulating tank from a high position in which its lateral surface is partly covered by the insulating tank.

According to one embodiment, a pump ensures the forced circulation of the electrolyte in the insulating tank.

Advantageously, the height of the insulating tank is close to 750 mm.

Advantageously, the stroke of the mobile electrode is close to 600 mm.

BRIEF DESCRI PTI ON DES DESSI NS

Figure 1 is a simplified representation of an electrolyte resistance for an asynchronous motor of the prior art;

Figure 2 is a schematic sectional view of cylinder electrodes of an asynchronous motor of the prior art, after mutual insertion;

Figure 3 is a schematic view of electrodes according to an embodiment of the invention, in the close position;

Figure 4 is a schematic view of the electrodes of Figure 3 during reciprocal insertion;

Figure 5 is a radial sectional view of the fixed electrode of an asynchronous motor according to an embodiment of the invention;

Figure 6 is a plan view of the electrode of Figure 5;

FIG. 7 is a view in radial section of two electrodes in the final insertion position according to an embodiment of the invention;

Figure 8 is a schematic sectional view of an electrolyte resistor according to an embodiment of the invention;

FIG. 9 is a perspective view of two electrodes according to an embodiment of the invention, before insertion;

Figure 10 is a perspective view of two electrodes according to another embodiment of the invention.

DETAILED DESCRIPTION

In an asynchronous ring motor, for the mining or cement industry, it is customary to use, for each phase of the rotor, a variable resistance to ensure the starting of the motor. Usually, this resistance consists of an electrolyte tank in which are arranged a fixed electrode and a mobile electrode. In FIG. 1, the tank 1 is filled with electrolyte 2. The fixed electrode 3, placed at the bottom of the tank 1 is connected to the rotor of the engine. The movable electrode 4, movable vertically, is connected to ground. During the start-up sequence, the mobile electrode 4, initially at the top of the tank 1, is lowered and brought closer to the fixed electrode 3.

According to a known embodiment (FIG. 2), the fixed electrode 3 comprises two coaxial cylinders 5, 6, and the movable electrode 4 comprises an axis 7 and a cylinder 8, coaxial. When the movable electrode 4 is lowered in the vicinity of the fixed electrode 3, the axis 7 is inserted into the axis of the inner cylinder 5, and the cylinder 8 is inserted between the cylinders 5 and 6.

In the case of FIG. 1, the value of the resistance is a function of the distance d between the two electrodes 3 and 4, and of the surface of each of the disc-shaped electrodes. Between the initial position where the mobile electrode is at the top of the tank, and the final position, where it is at the bottom just opposite the fixed electrode, the resistance varies from Ri to Rf depending on the only distance d between the two electrodes.

In the case of FIG. 2, when the mobile electrode 4 is at the top of the tank, its apparent surface, seen from the fixed electrode 3, is the base surface of the cylinder 8, substantially equal to the surface of the electrode 4 of FIG. 1. The distance between the two electrodes is the distance between the free edges of the cylinders 8 and 6. When the mobile electrode 4 is inserted in the fixed electrode 3 (FIG. 2), the distance between the electrodes 3 and 4 is the radial distance between cylinders 8 and 6, or 8 and 5, or between axis 7 and cylinder 5. The surface to be taken into account is then the sum of the surfaces opposite axis 7 and cylinder 5 (inner face), cylinder 5 (outer face) and cylinder 8 (inner face), and cylinder 8 (outer face) and cylinder 6 (inner face). The larger this surface, the lower the resistance Rf. With this arrangement in coaxial cylindrical rings of the fixed and mobile electrodes, the values of the ratio Ri / Rf are usually between 80 and 100.

According to the invention, in Figure 3, the electrodes are constituted by rings of triangular section. The fixed electrode 13 has two coaxial rings 15, 16. The movable electrode 14 comprises a central cone 17 and a ring 18. In an axial plane, the section of the rings 15, 16, 18, and of the cone 17, is an isosceles triangle, the apex angle of which is between 3 and preferably 10 °. In the close position (FIG. 3), the distance d between the electrodes 13 and 14 is the distance between the vertices of the triangles corresponding to the rings 16 and 18 for example. This distance is around 16 mm. When the mobile electrode 14 is inserted into the fixed electrode 13 (FIG. 4), the distance between the electrodes, which is the distance between two opposite faces of the rings of triangular section, decreases until it is of the order of 3 mm, due to the triangular shape of the ring section. The facing surfaces of the electrodes are substantially of the same order of magnitude as in the case of cylindrical rings of the prior art, but due to the reduction in the distance between electrodes, the value of the final resistance is lower and the ratio Ri / Rf is practically doubled compared to the prior art.

In the practical embodiment of Figures 5 and 6, the fixed electrode 24 has a base 25 in the form of a cross on which are fixed coaxial rings 26, section in the general form of an isosceles triangle, separated by spaces 27 allowing the circulation of the electrolyte. The center 28 of the electrode is assigned to the electrical connection with the motor rotor. In this exemplary embodiment, the fixed electrode 24 has five coaxial rings 26. The corresponding movable electrode 29 has four rings. The relative arrangement of the electrodes during their approximation is represented in FIG. 9. At the end of insertion, the two fixed 24 and mobile 29 electrodes according to another embodiment, are represented in FIG. 7.

In the embodiment of FIG. 8, all of the fixed 31 and mobile 32 electrodes and of the electrolyte 33 are housed in an external reservoir 34. Inside the reservoir 34, a cylindrical insulating tank 35 d is disposed. vertical axis and diameter close to that of the electrodes

31, 32. The height of the tank 35 is close to 750 mm. The movable electrode 32 is moved in the tank 35 between a high position, where its lateral surface is partly covered by the insulating tank 35, and a low position where it is inserted in the fixed electrode 31. The insulating tank 35 ensures a line of current lines between the electrodes. Below the fixed electrode 31, is arranged a pump 36 which ensures a forced circulation of the electrolyte 33 in the tank 35 to extract the power dissipated between the electrodes, especially when they are close together. In this exemplary embodiment, the stroke of the mobile electrode 32 is close to 600 mm, while in the state of the art, this stroke is close to 300 mm.

Thus, with triangular profile electrodes, a high insulating tank and a long stroke of the movable electrode, the ratio Ri / Rf reaches a value of approximately 300.

In the embodiment of FIG. 10, the fixed 41 and mobile 42 electrodes are not of circular base but rectangular. The rings are replaced by prisms of triangular section, arranged parallel to each other.

The reciprocal insertion of the electrodes proceeds in the same manner as in the previous embodiments.

In another embodiment, the movement of the electrodes is organized along an axis not vertical but horizontal. The approximation of the electrodes is carried out either between a fixed electrode and a mobile electrode, or between two mobile electrodes. The amplitude of the relative movement of the electrodes can be greater, on the order of 1000 mm, and the electrolyte reservoir remains at a shallower depth.

Claims (13)

1- Asynchronous electric motor with rings comprising at the rotor, for each phase, a variable resistance of assistance to starting constituted by an electrolyte in which are placed two electrodes (13, 14), one of which (14) is mobile and l 'other (13) is fixed, characterized in that each of the electrodes (13, 14) comprises elements in relief (15, 16; 17, 18) of triangular section. 2- Motor according to claim 1 characterized in that the triangular section of the elements in relief (15, 16; 17, 18) is an isosceles triangle whose angle at the apex is between 3 and 15 °. 3- Motor according to one of claims 1 or 2 characterized in that the elements in relief of the electrodes have interpenetrating shapes. 4- Motor according to one of claims 1 to 3 characterized in that the elements in relief of the electrodes are prisms. 5- Motor according to one of claims 1 to 3 characterized in that the elements in relief of the electrodes are coaxial rings (26). 6- Motor according to claim 5 characterized in that the radii of the coaxial rings (26) of each electrode differ by a constant pitch. 7- Motor according to claim 6 characterized in that the radii of the coaxial rings of the movable electrode (14, 29) differ from the radii of the coaxial rings of the fixed electrode (13, 24) by half a step. 8- Motor according to one of claims 1 to 7 characterized in that the fixed (31) and mobile (32) electrodes are arranged in a cylindrical insulating tank (35) with a diameter close to that of the electrodes. 9- Motor according to claim 8 characterized in that the insulating tank (35) is vertical, the fixed electrode (31) is at the bottom of the insulating tank and the mobile electrode (32) is moved in the insulating tank (35) from a high position in which its lateral surface is partly covered by the insulating tank (35). 10- Motor according to one of claims 8 to 9 characterized in that a pump (36) ensures the forced circulation of the electrolyte (33) in the insulating tank (35). 11 - Motor according to one of claims 8 to 10 characterized in that the height of the insulating tank (35) is close to 750 mm. 12- Motor according to one of claims 8 to 11 characterized in that the stroke of the movable electrode (32) is close to 600 mm. 16 ^z