ANALYSIS OF AN ASYNCHRONOUS MOTOR SYSTEM WITH A FREQUENCY CONVERTER
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Abstract
In the frequency converter system, there is no state of inertia. The increase in torque is linear. As a result, sufficient efficiency is given to increase the service life of mechanical transmission parts. Another advantage of frequency converter devices is its wide speed control range. By setting the frequency of the alternating current supplied to the alternating current input at the desired value, we can linearly change the speed of the electric conductor from zero to the maximum value.
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Yuldasheva M.A.
Assistant of Islam Karimov Tashkent State
Technical University Almalyk branch
Abstract: In the frequency converter system, there is no state of inertia. The increase in torque is linear. As a result, sufficient efficiency is given to increase the service life of mechanical transmission parts. Another advantage of frequency converter devices is its wide speed control range. By setting the frequency of the alternating current supplied to the alternating current input at the desired value, we can linearly change the speed of the electric conductor from zero to the maximum value.
Key words: Frequency converter, source, consumer, electrical filters.
The generator is one of the first systems to take the place of the engine system. A thyristor is used as a frequency converter element. The start-up and speed adjustment functions of the asynchronous motor, which is used as a driver, are performed by adjusting the impulse values given to the control electrode of the thyristors. Since it is possible to use the thyristor rectifier as an electronic switch, this device also has the possibility to use the protection function in various emergency situations.
Figure 1. Frequency converter-asynchronous motor system operating mechanism.
Drilling machines have up to 12 electric drives designed for various tasks. In terms of their principle of operation, it is necessary to adjust the speed of the main three electric drives. If the main electromechanical parts are used as a control device for electric drives, asynchronous motors with frequency converters are used, and the rest of the electric drives should be controlled using direct start-up adjustment devices. The advantage of this system is that it does not require changing the type of excess current, does not use additional resistances that consume excess energy to adjust the speed, and smooth transition of the wire adjustment and power control. If we take the example of the SBSH machine tools, with the increase of the drilling depth, the loading force on the drill rod increases. A sudden speed change in the process of increasing the torque leads to a sudden inertia of the mechanical transmission parts and mechanical damage during a large torque change. In the frequency converter system, there is no state of inertia. The increase in torque is linear. As a result, sufficient efficiency is given to increase the service life of mechanical transmission parts.
Another advantage of frequency converter devices is its wide speed control range. By setting the frequency of the alternating current supplied to the alternating current input at the desired value, we can linearly change the speed of the electric conductor from zero to the maximum value.
Figure 2. The principle of operation of the asynchronous motor system with a frequency converter
Semiconductor frequency converter - the device mainly consists of three main parts, in the first part the alternating current is rectified using rectifiers, in the second part the rectified alternating current is filtered, in the third part the filtered direct current is converted back to alternating current with the frequency changed. Their opening and closing levels are controlled by the signal given to the control fields of thyristors or transistors used in the third part. The number of openings and closings can be controlled by an impulse control system that signals the control area of the device.
The frequency converter is fundamentally different from the generator motor system and the thyristor rectifier motor system due to the increased number of mechanical transmissions occurring in the asynchronous motor system and the absence of losses in the DC chain, as well as the useful work coefficients of the transmissions. will be somewhat higher.
Below is the network connection diagram of an asynchronous motor controlled by a frequency converter. Distribution of the useful work coefficients of the shunt converter and asynchronous motor connected to the network with the help of a throttle, as well as for each of its parts. If we talk about the working principle of the frequency converter system, its input part from the network is equipped with a throttle device to perform the task of adjusting the high harmonic currents and the voltage value in the converter circuit.
The input voltage is rectified by an AC rectifier device, after which the residual harmonics are fully smoothed by filtering devices to smooth the currents. The smoother the harmonics of the rectified current, the greater its adjustment value and range.
Figure 3. The scheme of calculation of useful work coefficients on the structural parts of the frequency converter asynchronous digital system.
Frequency converters are devices designed to convert alternating current or voltage of one frequency into alternating current or voltage of another frequency.The output frequency of modern frequency converters can vary over a wide range and can be higher or lower than the mains frequency.Any circuit of frequency converters consists of power and control parts. The power part usually consists of thyristors or transistors working in the mode of electronic switches. The control part is implemented in digital microprocessors, and the power part provides control of electronic switches, as well as solving a large number of auxiliary tasks (control, diagnostics, protection).
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