SU1665446A1 - Brush for electric machine - Google Patents

Abstract

The invention relates to electrical engineering in the field of creating brushes for use in DC electric machines with a short-term one-time operation mode and high-density operating currents. The aim of the invention is to reduce sparking during operation of the brush in a short-term one-time mode under the conditions of switching currents of high densities by ensuring a smooth change in the transient resistance of adjacent sections. The design is a bundle of insulated conductive cores 4 made of metal with low ohmic resistance, fixed from the non-working end of an insulating sleeve having an opposite end with a saw-tooth profile. In the casing 1, tires 7 are placed, having electrical contact with the core layer 4, forming section 2. The sections are arranged parallel to the collector plates of the collector 6 and are connected to each respective resistor 3. The resistance value of the current-limiting resistors 3, which also play the role of thermal radiators, increases in the direction of running around the edges of the body electrobrush. The sawtooth profile of the cage is formed by a number of inclined planes whose angle of inclination relative to the upper end of the cage is determined from the conditions for optimizing the range of displacement of the working ends of the lived in the tangential direction. This makes it possible to improve the switching parameters of the brush by means of a smoother fall of the current in the working circuit of the machine, as well as a decrease in heat generation in the area of the sliding contact. 3 il.

Description

The conductive sections 2 are insulated with each other, with resistors 3 attached to them, the resistance of which increases from the incident edge to the running edge of the brush. Each section 2 is made of insulated current-carrying veins 4 of a material of high elasticity, low ohmic resistance, such as beryllium bronze, and with an insulating coating, such as varnish. At the same time, the working ends 5 of the cores 4 of each section 2 are free from the clamping of the holder 1 and are capable of creating multiple contacts with the collectors of the electric machine with their ends, and the non-working ends of the sections of the sections fastened with the holder have electrical contact created, for example, by reduction, with stock tires. The tires are insulated from one another by partitions of the upper end 8 of the cage. Each of the buses is connected to one of the ends of the current-absorbing resistors 3. The other ends of all resistors are connected to a common current collector 9. The lower end 10 of the yoke 1 is made as a series of planes inclined relative to the upper end of the yoke 11. The number of inclined planes corresponds to the number of brush sections . The brush is designed for electrical machines with short-term one-time operation. In this connection, its structure takes into account a very low wear height and is able to work without a pressing mechanism. The necessary force of pressing the brush to the collector is provided by the elasticity of the cores, the length of the free part of which exceeds the distance between the corresponding point of the lower end surface and the collector. The calculation of the design parameters of the brush is based on an estimate of the intensity of sparking during dynamic mixing of adjacent layers of the adjacent sections, which ensures a smooth increase in the brush's transient resistance during ejection from the collector plate. It has been established experimentally that the degree of intensity of sparking decreases significantly with increasing penetration of adjacent layers of the veins to 15-20% of the width of the sections. Deeper penetration of the layers has practically no effect on the reduction of the spark quantity (the evaluation was carried out according to the amplitude of the voltage fluctuation of the radio interference meter). Taking these numbers beyond the boundary conditions when determining the design parameters of the brush and given the width of the sections d, the installation height of the brush holder above the collector H and the gap between adjacent sections I, the optimal deviation of the section’s escaping layers is found by calculating the angle a

the clone plane of the bottom end of the cage, determined from the relationship (see Fig. 2). I 0.15-0.20 d h -H

Then, considering that h d tga, finally have

one

H

HI

0.15 -0.20 d2 -arctg K

where K is a dimensionless coefficient characterizing the optimal range of displacement of the working ends of the cores of the sections during rotation of the electric machine collector. During the operation of the electrical machine (FIG. 3), the working ends of the cores 4 slide along the collector b, forming multiple contact with the collector plates due to the degree of freedom of each elastic core. The frontal layers of the veins of each section 2 due to the effect of friction deviate from the initial vertical position in the direction of rotation of the collector. The degree of deviation of each of the layers is determined by different lengths of their working ends 5, which makes it possible to introduce the escaping layers of one section into the oncoming layers of another and is limited by the edge of the inclined plane 11. The working current in the brush is determined by the sum of parallel currents of the sections. The change in transitional contact with the passage of the collector plates under the brush sections connected to resistors with an abruptly changing nominal value is noticeably limited by mixing the boundary layers of the adjacent sections. In this case, the shorting of the working ends of the adjacent sections prevents the insulating coating on each core. Thus, the construction of the body sections from vertically arranged conductive cores makes it possible to create a blurred boundary between two adjacent sections. The presence of sections of the insulating layer on each core allows one to exclude shorting of the working sections of the cores of adjacent sections when they are mechanically touching; The lower end of the insulating cage in the form of a series of parallel inclined planes designed to fix the veins of each section allows the frontally located layers of the veins of one section to have different degrees of freedom and determines the possibility of dynamic penetration of the boundary layers of two adjacent sections into each other. Due to this, in the proposed brush, compared with the known, the prerequisites for spark formation are reduced with a significant decrease in the transient resistance in the area of the sliding contact, which makes it possible to successfully use it in electric machines with a one-time short-term mode of operation at high current densities (200A / CM2 and more). ).

F o rm ula invention

A brush for an electric machine, containing a holder of dielectric material and vertically fixed in it insulated between themselves conductive sections with resistors connected to them, the resistance of which increases from the incident brush to the escaping edge of the brush, characterized in order to reduce sparking during operation brushes in the short-term one-time mode in terms of switching currents of high densities due to

ensuring a smooth change in transition resistance of adjacent sections, each section is made of coatings by insulating conductive veins, the bottom end of the cage contains a row equal to the number of sections obliquely located relative to the top end of the cage, the planes, and the angle of inclination of these planes is chosen from the condition

and arctd K

HI d2

where H is the height of the brush clip installation above the electrical machine collector;

I is the gap between adjacent sections;

d is the width of the sections;

K is a dimensionless coefficient characterizing the optimum range of displacement of the working ends of the lived in the tangential direction.

eight

FIG. 2

Claims (1)

Claim A brush for an electric machine containing a holder of dielectric material and vertically mounted in it insulated conductive sections with resistors connected to them, the resistance of which increases from the brush running towards the runaway edge, characterized in that, in order to reduce sparking during brush operation in the short-term one-time mode in conditions of switching currents of high densities by ensuring a smooth change in the transition resistance of adjacent sections, each section is made of insulation coatings of conductors. the lower end of the cage contains a series equal to the number of sections obliquely located relative to the upper end of the cage, planes, while the angle a of the inclination of these planes is selected from the condition a = arctd K Hi d ² 1 q where H is the mounting height of the brush holder over the collector of the electric machine; I - the gap between adjacent sections; d is the width of the sections; K is a dimensionless coefficient characterizing the optimal range of displacement of ¹⁵ working ends of the wires in the tangential direction. Figure 2 \ Phi & Z