Most machine tools at repair plants are designed on the principle of measuring the magnitude of the imbalance vector by the maximum deflection of the supports at resonant rotation frequencies. This measures the magnitude of the vector. The direction of the vector is fixed by the tracking system according to the angle of rotation of the body of rotation being tested. The indicators are summarized in the measuring device, according to the mutual reaction of the device coils, according to the principle of an electrodynamic wattmeter.

Initially, the existing imbalance is measured. Its correction consists of installing balancing weights provided for in the product drawing in the direction directly opposite to the measured vector. Or in a small removal of metal in the direction strictly corresponding to the measured vector.

Loads, depending on the design of the unit, are secured temporarily or permanently. The vector is re-measured and the installed weights are adjusted, or they are finally secured as provided by the design, if the value of the residual imbalance corresponds to the permissible

Serially produced dynamic balancing machines

Machines produced by the Minsk Machine Tool Plant, types 9717, 9718, 9719, are very widely used. This equipment has significant dimensions and requires large volumes of reinforced concrete foundations for installation. They carry out balancing of parts and assembly units from 0.5 to 5.0 tons. These are anchors electric machines and wheelsets. Since the mid-80s, the design of generator armature flanges has been changed. The outer surface of the socket for installing the centering ring is made in the form of an elongated collar cylindrical, which can directly serve as a base surface for dynamic balancing of the armature. This made it possible to avoid installing additional bushings, reduce the complexity of the operation and increase its accuracy.

Fig. 20 Balancing the armature on the 9719 machine

New generation of machines

IN lately factories have produced a new generation of balancing machines offered on the market today. In particular, these are machines from the DIAMECH company. A special feature of the machines is that the imbalance is measured not due to the maximum deflection of the moving bearing supports, but due to the reaction of the rigidly fixed supports. In this case, the reaction itself is measured as a stress value using a strain gauge method using built-in sensors. All results are summarized and processed on a computer built into the machine with information displayed on the display.

This design The machine does not require foundations for its installation. The machine is installed directly on the floor surface. The dimensions of these machines are slightly larger than the dimensions of the product being balanced.

Fig. 21 Dynamic balancing on the VM3000 machine from DIAMECH

A very characteristic detail for new generation machines is the absence of a foundation and the transmission of rotation by a belt drive.

Unbalance of any rotating part Failure of a diesel locomotive can occur both during operation due to uneven wear, bending, accumulation of contaminants in any one place, when the balancing weight is lost, and during the repair process due to improper processing of the part (displacement of the axis of rotation) or inaccurate alignment of the shafts. To balance the parts, they are subjected to balancing. There are two types of balancing: static and dynamic.

Rice. 1. Scheme of static balancing of parts:

T1 is the mass of the unbalanced part; T2 is the mass of the balancing load;

L1, L2 - their distances from the axis of rotation.

Static balancing. For an unbalanced part, its mass is located asymmetrically relative to the axis of rotation. Therefore, in the static position of such a part, i.e. when it is at rest, the center of gravity will tend to take a lower position (Fig. 1). To balance the parts, they are added diametrically opposite side load with mass T2 so that its moment T2L2 is equal to the moment of the unbalanced mass T1L1. Under this condition, the part will be in balance in any position, since its center of gravity will lie on the axis of rotation. Equilibrium can also be achieved by removing part of the metal of the part by drilling, sawing or milling from the side of the unbalanced mass T1. In the drawings of parts and in the Repair Rules, a tolerance is given for balancing parts, which is called imbalance (g/cm).

Flat parts that have a small length-to-diameter ratio are subjected to static balancing: the gear wheel of a traction gearbox, the impeller of a refrigerator fan, etc. Static balancing is carried out on horizontally parallel prisms, cylindrical rods or on roller supports. The surfaces of prisms, rods and rollers must be carefully processed. The accuracy of static balancing largely depends on the condition of the surfaces of these parts.

Dynamic balancing. Dynamic balancing is usually carried out on parts whose length is equal to or greater than their diameter. In Fig. Figure 2 shows a statically balanced rotor, in which mass T is balanced by a load of mass M. This rotor, when rotating slowly, will be in equilibrium in any position. However, with its rapid rotation, two equal but oppositely directed centrifugal forces F1 and F2 will arise. In this case, a moment FJU is formed which tends to rotate the rotor axis through a certain angle around its center of gravity, i.e. there is a dynamic imbalance of the rotor with all the ensuing consequences (vibration, uneven wear, etc.). The moment of this pair of forces can only be balanced by another pair of forces acting in the same plane and creating an equal reaction moment.

To do this, in our example, we need to apply two weights of masses Wx = m2 to the rotor in the same plane (vertical) at an equal distance from the axis of rotation. The loads and their distances from the axis of rotation are selected so that the centrifugal forces from these loads create a moment /y counteracting the moment FJi and balancing it. Most often, balancing weights are attached to the end planes of parts or part of the metal is removed from these planes.

Rice. 2. Scheme of dynamic balancing of parts:

T—rotor mass; M is the mass of the balancing load; F1, F2 - unbalanced, reduced to the rotor mass planes; m1,m2 - balanced, reduced to the rotor mass planes; P1 P 2 - balancing centrifugal forces;

When repairing diesel locomotives, dynamic balancing is carried out on such rapidly rotating parts as the rotor of a turbocharger, the armature of a traction motor or other electrical machine, impeller blowers assembled with a drive gear, water pump shaft assembled with an impeller and gear, cardan shafts for driving power mechanisms.

Rice. 3. Diagram of a console-type balancing machine:

1 - spring; 2 — indicator; 3 anchor; 4 - frame; 5 — machine support; 6 — bed support;

I, II - planes

Dynamic balancing is in progress on balancing machines. Schematic diagram such a console-type machine is shown in Fig. 3. Balancing, for example, the armature of a traction motor is carried out in this order. The anchor 3 is placed on the supports of the swinging frame 4. The frame rests with one point on the support of the machine 5, and the other on the spring 1. When the armature rotates, the unbalanced mass of any of its sections (except for the masses lying in plane II - II) causes the frame to swing. The amplitude of frame vibration is recorded by indicator 2.

To balance the anchor in the I-I plane, test weights of different masses are attached alternately to its end on the side of the collector (to the pressure cone) and the frame oscillations are stopped or reduced to an acceptable value. Then the anchor is turned over so that plane I—I passes through the fixed support of the frame 6, and the same operations are repeated for plane II—II. In this case, the balancing weight is attached to the rear pressure washer of the armature.

After completion of all assembly work, the parts of the selected sets are marked (with letters or numbers) in accordance with the requirements of the drawings

For dynamic balancing The most convenient is a resonance type machine, consisting of two welded stands, support plates and balancing heads. The heads consist of bearings, 6 segments and can be fixed with bolts or freely swing on the segments.

The balanced rotor is driven into rotation by an electric motor. The release clutch serves to disconnect the rotating rotor from the drive during balancing.

Dynamic rotor balancing consists of two operations: measuring the initial vibration value, which gives an idea of ​​the size of the imbalance of the rotor masses; finding the placement of the bale and determining the mass of the balancing load for one of the ends of the rotor.

During the first operation of the head the machine is secured with bolts. The rotor is driven into rotation using an electric motor, after which the drive is turned off by disengaging the clutch and one of the machine heads is released.

The released head swings under the action of the radially directed centrifugal force of the unbalance, which allows the dial indicator 3 to measure the amplitude of the head oscillation. The same measurement is made for the second head.

The second operation is performed by the “cargo bypass” method. Having divided both sides of the rotor into six equal parts, a test load is alternately fixed at each point, which should be less than the expected unbalance.

The vibrations of the head are then measured using the method described above for each position of the load. The most advantageous location for placing the load will be the point at which the vibration amplitude was minimal.

The mass of the balancing weight Q is obtained from the expression:

Where: P is the mass of the test load; TO 0 - initial amplitude of oscillations before walking around with a test load; TO min - minimum amplitude of vibrations when walking around with a test load.

43. Sequence of operations when assembling electrical machines after repair.

General machine assembly AC includes: installation of bearings, insertion of the rotor into the stator, pressing of bearing shields, measurement of air gaps. The rotor is inserted using the same devices that are used during disassembly. This operation requires great attention and experience when assembling large machines, since even a light touch of a massive rotor can lead to significant damage to the windings and cores.

The assembly sequence and its labor intensity are primarily determined by the complexity of the electrical machine design. Easiest assembly asynchronous motors with a squirrel-cage rotor.

First, prepare the rotor for assembly by placing ball bearings on the shaft. If the bearing supports have internal covers, they are first placed on the shaft, filling the sealing grooves with lubricant. Bearings are secured to the shaft with a retaining ring or nut, if provided for by the design of the machine.Roller bearings are divided into two parts: The inner ring together with the rollers is mounted on the shaft, the outer ring is installed in the shield.

After the rotor is inserted into the stator, grease is placed in the bearings, the shields are put on the bearings and pushed into the housing with centering belts, secured with bolts. All bolts are initially screwed into several threads, then, alternately tightening them at diametrically opposite points, the shield is pressed into the body. After assembly, check the ease of rotation of the rotor and run it at idle, checking the bearings for heat and noise. The engine is then sent to a testing station.

Machine assembly DC start with preparing the armature, inductor and bearing shields.

A fan is pressed onto the armature, consisting of a shaft, a core with a winding, a collector and a balancing ring. The inner bearing caps are placed on both ends of the shaft and the ball bearings are pressed into place. For roller bearings, only the inner ring is pressed on. A shield is pressed onto the outer ring of the bearing on the side opposite to the commutator. Lubricant is placed in the bearing and closed with an outer cover.

Assembling the inductor includes installing the main and additional poles with coils into the housing and making connections between the coils. The poles are first pressed into the coils, installing gaskets, frames, springs, etc. The coil or frame that rests on it must protrude above the surface of the back of the pole to ensure reliable clamping of the coils when tightening the pole mounting bolts.

The assembler supports small poles with coils by hand during installation; heavy poles are first secured to the fixture with staples or other means. The device shown in the figure is designed for installing poles with the housing in a vertical position and consists of a round base, a central rod for lifting and transportation, and a lever-hinge mechanism that ensures the poles are pressed after the device is lowered into the housing under the influence of its own weight.

The coils of the main and additional poles are connected according to the diagram. Depending on the insulation class, the joints are insulated with several layers of varnished cloth or fiberglass cloth and a protective tape on top. Rubber bushings are placed on the flexible leads where they pass through the walls of the frame, protecting the insulation of the leads from damage.

The polarity of the poles is checked in the assembled inductor using a compass. The winding is connected to a direct current source, the compass is moved around the circle near the poles. Near each adjacent pole, the arrow should rotate 180°. In the direction of rotation in engines, the main pole is followed by an additional pole of the same name, in generators - an additional pole of a different polarity.

The shield on the commutator side is prepared for assembly by installing a set of brush holders into it and connecting it according to the diagram.

The general assembly of DC machines begins with pressing the front (collector) shield into the inductor. This operation is usually performed with the inductor in a vertical position. The shield is inserted from above and pressed into the body with fastening bolts. The armature is inserted and the rear shield is pressed in with a vertical or horizontal inductor. When assembling vertically, the anchor with the shield is lifted by an eye bolt, which is screwed onto the threaded end of the shaft.

Assembly is final technological process, the quality of execution of which largely determines the energy and operational performance of machines - efficiency, level of vibration and noise, reliability and durability. Assembly must be carried out using parts and assembly units belonging to this machine, since impersonal assembly is more complex organizationally and there may be cases when the characteristics of the machine do not meet the requirements of the standards. The quality of assembly is influenced by the correct organization of the workplace and the use of working tools. The assembled machine is run-in and tested.

§ 10.1. Balancing rotors and armatures

Before assembly, the rotors (armatures) and other rotating parts are balanced if they have been repaired or if increased vibration was detected during pre-repair tests. According to GOST 12327-79, compensation for imbalance must be carried out in two correction planes when the ratio of the axial dimension L of the part to the diameter D is greater than 0.2; at L/D<0,2 - в одной плоскости. Детали, устанавливаемые на отбалансированный ротор, балансируются отдельно. Если деталь устанавливают на ротор (якорь) с помощью шпонки, то она балансируется со шпонкой, а ротор - без шпонки.

With one correction plane, the rotor (armature) can be balanced both statically and dynamically, and with two planes - only dynamically.

Static balancing. The rotor is balanced on prisms (10.1). The deviation of the prism plane from the horizontal plane should not exceed 0.1 mm per 1 m of prism length. The surface roughness of the prisms should be no worse

The rotor (anchor) is installed on the prisms and with a slight push it is brought out of balance, giving it the opportunity to roll along the prisms. After several swings, the unbalanced rotor (armature) will stop. A test load is installed at the top point of the rotor and the experiment is repeated. This is done several times and the load is selected. The rotor is considered balanced if it stops without swinging in a state of indifferent equilibrium. The test weight is weighed and a standard weight equal in weight to the test weight is installed in its place.

If the parts being balanced do not have a shaft, then a technological shaft is made on which balancing is performed.

Dynamic balancing. The rotor is balanced on the machine as it rotates. Modern balancing machines allow you to determine the installation location and weight of the load. Their use in repairs is highly desirable, but with a large range of machines being repaired, private readjustment reduces the efficiency of the machines and their use is not always justified. The use of a universal balancing machine allows you to solve this problem (10.2).

The balanced rotor 4 is mounted on four round supports 2 and 6. The supports are located on a frame 7, consisting of two round beams. Engine 5 drives the rotor through belt 3. The left side of the frame is attached to the base by a flat spring 1 and remains motionless when the rotor rotates, while the right side rests on springs 9 and when the rotor rotates it begins to oscillate under the influence of the unbalanced masses of the right side of the rotor.

The magnitude of the oscillations is shown by dial indicator 8. After determining the magnitude of the oscillations, stop the rotor and hang a test weight (plasticine) on the right side of the rotor. If during the next rotation the magnitude of the oscillations increases, this means that the test weight is installed incorrectly. By moving the load around the circle, they find the place where its location causes the least vibration. Then they begin to change the mass of the test load, achieving a minimum of vibrations. Having balanced the right side, remove the test weight and install a constant weight. The rotor is then turned and the other side is balanced.

April 4, 2011

For static balancing, a machine is used, which is a supporting structure made of profile steel with trapezoidal prisms installed on it. The length of the prisms must be such that the rotor can make at least two revolutions on them.

The width of the working surface of the prisms a is determined by the formula:

Where: G—load on the prism, kg; E is the elastic modulus of the prism material, kg/cm2; p - design specific load, kg/cm 2 (for hard hardened steel p = 7000 - 8000 kg/cm 2); d—shaft diameter, cm.

In practice, the width of the working surface of the prisms of balancing machines for balancing rotors weighing up to 1 ton is taken to be 3 - 5 mm. The working surface of the prisms must be well polished and capable of supporting the weight of the rotor being balanced without deformation.

Machines for balancing rotors (armatures) of electrical machines:

a - static, b - dynamic;

1 - stand, 2 - balanced rotor, 3 - dial indicator, 4 - release clutch, 5 - drive motor, b — segments, 7 - clamping bolts, 8 - bearing, 9 - plate.

Static balancing of the rotor on the machine is carried out in the following sequence. The rotor is placed with the shaft journals on the working surfaces of the prisms. In this case, the rotor, rolling on the wheels, will take a position in which its heaviest part will be at the bottom.

To determine the point on the circle at which the balancing weight should be installed, the rotor is rolled five times and after each stop, the lower “heavy” point is marked with chalk. After this, there will be five chalk lines on a small part of the rotor circumference.

Having marked the middle of the distance between the extreme chalk marks, the point of installation of the balancing weight is determined: it is located in a place diametrically opposite to the average heavy current. At this point the balancing weight is installed.

Its mass is selected experimentally until the rotor stops rolling when stopped in any arbitrary position. A properly balanced rotor, after rolling in one direction and the other, should be in a state of indifferent equilibrium in all positions.

If it is necessary to more completely detect and eliminate the remaining imbalance, the rotor circumference is divided into six equal parts. Then, placing the rotor on the prisms so that each of the marks is alternately on the horizontal diameter, small weights are alternately hung at each of the six points until the rotor comes out of rest.

The masses of cargo for each of the six points will be different. The smallest mass will be at the heavy point, the largest at the diametrically opposite point of the rotor.

With the static balancing method, the balancing weight is installed only at one end of the rotor and thus eliminates static unbalance.

However, this balancing method is applicable only for short rotors of small and low-speed machines. To balance the masses of the rotors of large electrical machines (power over 50 kW) with high rotation speeds (more than 1000 rpm), dynamic balancing is used, in which a balancing weight is installed at both ends of the rotor.

This is explained by the fact that when the rotor rotates at high speed, each end of it has an independent runout caused by unbalanced masses.

“Repair of electrical equipment of industrial enterprises”,
V.B.Atabekov

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