Chastotnik for the electric motor with their own hands: circuit, instruction and connection

In this article, we will consider aelectric motor, the principle of its operation and the main components. The main emphasis will be placed on the theory, so that you understand the principle of operation of the frequency converter and could later carry out design and manufacturing with your own hands. But first you need a small introductory course, which will tell you what a chastotnik is and for what purpose it is needed.

Functions of the frequency converter

The lion's share is in the industryasynchronous motors. And it was always difficult to control them, because they have a constant rotor speed, and changing the input voltage is very difficult, and sometimes even impossible. But the chastotnik reverses the picture completely. And if earlier to change the speed of the conveyor, for example, used a variety of reducers, then today it is enough to apply one electronic device.

In addition, the frequencyonly the possibility of changing the parameters of the drive, but also several additional degrees of protection. There is no need for electromagnetic starters, and sometimes even do not need a three-phase network to ensure the normal operation of the induction motor. All these duties associated with switching and turning on the drive are transferred to the frequency converter. It allows you to change the phases at the output, the frequency of the current (and therefore the rotor speed varies), carry out the start and brake adjustment, and many other functions can be realized. It all depends on the microcontroller used in the control circuit.

Operating principle

Make a chastotnik for the electric motorThe diagrams of which are given in the article are quite simple. It allows you to convert one phase into three. Consequently, it becomes possible to use an asynchronous motor in everyday life. At the same time, its efficiency and power are not lost. After all, you know that when you turn on the motor in a network with a single phase, the reduction of these parameters almost doubles. And it's all about several transformations of the voltage coming to the input of the device.

The first is the rectifier block. More details about it will be described below. After the rectified voltage is filtered. And a pure direct current flows to the input of the inverter. It carries out the conversion of a direct current into an alternating current with the required number of phases. This cascade can be subjected to adjustments. It consists of semiconductors, to which a microcontroller control circuit is connected. But now about all the nodes in more detail.

Rectifier block

It can be of two types - single- and three-phase. The first type of rectifier can be used in any network. If you have a three-phase, then it's enough to connect to one. Scheme chastotnika for the electric motor is not complete without a rectifying unit. Since there is a difference in the number of phases, it means that it is necessary to use a certain number of semiconductor diodes. If we are talking about frequency converters, which are fed from one phase, then a rectifier of four diodes is required. They are switched on by bridge circuit.

It allows you to reduce the difference between the valuevoltage at the input and output. Of course, one half-wave circuit can be used, but it is inefficient, a large number of oscillations arise. But if it is a question of a three-phase connection, then it is necessary to use six semiconductors in the circuit. Exactly the same scheme in the rectifier of the car generator, there are no differences. The only thing that can be added here is three additional diodes designed to protect against reverse voltage.

Filter elements

After the rectifier there is a filter. Its main purpose is to cut off the entire variable component of the rectified current. For a clearer picture, it is necessary to draw up a replacement scheme. So, plus passes through the coil. And then between the plus and minus the electrolytic capacitor is switched on. Here it is and is interesting in the replacement scheme. If the coil is replaced by reactive resistance, then the capacitor, in the presence of a different current, can be either a conductor or a rupture.

As was said, in the rectifier at the outputD.C. And when it is fed to the electrolytic capacitor, nothing happens, since the latter is a break in the circuit. But there is a small variable in the current. And if an alternating current flows, then in the replacement circuit, the capacitor becomes a conductor. Consequently, the plus sign is closed to minus. These conclusions are made according to the laws of Kirchhoff, which are basic in electrical engineering.

Power Transistor Inverter

And now we got to the most important node -cascade transistors. They made an inverter - DC / AC converter. If you make a chastotnik for an electric motor with your own hands, then it is recommended to use IGBT transistor assemblies, you can find them in any store of radio components. Moreover, the cost of all components for the manufacture of chastotnik will be ten times less than the price of the finished product, even of Chinese production.

Two transistors are used for each phase. They are included between the plus and minus, as depicted in the diagram given in the article. But each transistor has a special feature - control output. Depending on which signal is sent to it, the properties of the semiconductor element change. Moreover, it can be done either by using manual switching (for example, using several microswitches to apply voltage to the necessary control terminals) and automatically. That's the last and will be discussed further.

Control scheme

And if the connection of the inverter tothe motor is simple to perform, it is enough just to connect the corresponding conclusions, then everything is much more complicated with the control circuit. The thing is that there is a need to program the device in order to achieve the maximum possible adjustments from it. At the core is a microcontroller, it connects to the reading devices and the executive. So, it is necessary to have current transformers that will constantly monitor the power consumed by the drive. And in case of excess should happen chastotnik.

Control circuit connection

In addition, overheating protection is provided. The output of the microcontroller using a matching device (Darlington assembly) is connected to the control terminals of the IGBT transistors. In addition, you need to visually monitor the parameters, so you need to include in the scheme LED-display. Readers need to add buttons that allow switching between programming modes, as well as variable resistance, rotating it changes the speed of rotation of the rotor of the electric motor.

Conclusion

It should be noted that you can makeChastotnik for an electric motor, the price of the finished product starts from 5,000 rubles. And this is for electric motors whose power does not exceed 0.75 kW. If you need to manage a more powerful drive, you need a more expensive one. For use in everyday life, the scheme described below is sufficient. The reason - there is no need for a large number of functions and settings, the most important thing is the possibility of changing the rotor speed.