From where you can choose a frequency converter. Frequency converter selection. Frequency converter regulation range

Many electrical devices used both for household and industrial purposes need a frequency converter - a device that makes it possible to change the frequency pulse of an electric current, at the same time changing its voltage. Most often, such devices convert a single-phase current into a three-phase one, or vice versa, lowering (increasing) the voltage in the ranges of 220-380 V. Very often, such products are used to adjust the speed of a synchronous or asynchronous motor. Thus, the motor can perform its functions more efficiently, and the result is good.

What is a frequency converter?

Any frequency converter consists of a number of circuits, which include a transistor, a thyristor, and a microprocessor that controls power type electronic keys. Modern models offer numerous additional functions, including protection, diagnostics, and comprehensive monitoring. Most often, devices today use the principle of pulse-width modulation, which has established itself as efficient and effective in practical application. A convenient adjustment system makes it possible to set the desired type of output voltage and current value.

What to consider when choosing a frequency converter?

To choose the most suitable model for yourself, one should proceed from the specific design features of the models, namely: its power, size, weight, mobility, the presence of vector or scalar control over the motor, the type of electric drive, and so on. At the same time, it should be borne in mind that the presence of a special speed sensor - an encoder, which allows you to achieve the required readings in terms of the required efficiency.

This German-made frequency converter has a built-in choke, EMC filter, and a power disconnect. Due to their compactness and easy maintenance, such devices are widely used not only in industrial but also in domestic applications. An efficient cooling system through the back channel makes it possible to operate the device practically without interruption, and with an output efficiency of up to 98%.

The price of the Danfoss VLT HVAC Basic Drive FC 101 5.5 kW model in Russia is about 48 thousand rubles.

The used models of Siemens frequency converters are distinguished by high reliability and versatility of application, including fans, pumps, compressors, conveyors and so on. With a voltage range of 208-240 V +/- 10% 380-480 V +/- 10%, the efficiency of the models is about 97%. At the same time, a complex braking system, including dynamic, combined and generator braking, reliably protects the device from overheating, blocking and short circuit.

The cost of the Siemens 6SE6420-2AC23-0CA1 model is about 24 thousand rubles.

Modern devices of the MICROMASTER brand are distinguished by an innovative design, a microprocessor control system, as well as a low noise level during operation. Thanks to pulse-width modulation, as well as IGBT transistors, many devices of this company are used for protective functions. With 2 analog inputs, 8 digital inputs, modular design, and external communication options, these frequency converters have proven themselves very well.

The price of the MICROMASTER 420 model is 12.2 thousand rubles.

How to make a remote control yourself and connect a frequency converter (video)

Photo: kub-privod.ru, nasos-reduktor.fis.ru, fainaidea.com

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We manufacture and sell frequency converters for converting a 220V household network into three phases, for controlling the speed of electric motors and smooth start-stop.
Model Power Price
CFM110 0.25kW 90 USD
CFM110 0.37kW 95 USD
CFM110 0.55kW 100 USD
CFM210 1.0 kW 130 USD
CFM210 1.5 kW USD 140
CFM210 2.2 kW USD 155
CFM210 3.3 kW USD 170
AFM 210/310 7,5 kW 400 USD

It is possible to connect the radio remote control to the frequency converter as in the video:

Photo of the radio remote control and frequency converter CFM110:

The price of the radio remote control is 30 USD
Delivery of chastotniki around the world by the EMC service at the expense of the consumer
Contacts for orders of frequency converters:
+38 050 4571330
[email protected] site

How to choose a frequency player

The author of these lines had to help clients many times in choosing various devices, one way or another related to the control of asynchronous motors, to put these devices into operation, and also, if possible, to correct mistakes made at the selection stage. This article summarizes some experience in this matter and is designed to help the end user choose the right equipment.

Have you ever been to an industrial plant? Well, yes, you work there ... You go into the shop, and there everything rumbles, hoots, rises, falls, cuts, spins - in a word, moves. If this is not about you, then you can not read this article further - everything that is written in it is somehow connected with movement. Often the quality and cost of the final product depends on how this movement takes place, be it a car or hot water from a boiler room. And the movement depends on the engine. What is the cheapest and most reliable engine today, and therefore the most common? That's right, asynchronous. AC induction motor with a squirrel cage rotor, to be precise and give our motor honor and respect. Otherwise, he will be offended and burn out inadvertently, and there will be equipment downtime and under-production. He is a capricious guy, and stubborn at times. Provide him with a sevenfold starting current, thermal protection, mood ... And he will agree to spin quickly. And if we don't need it quickly? If we don't need its 2950 rpm? That's right, you can find a slower engine, then it will be 1480 or something like that. Or 950. And if you need 2300? Or is it necessary to change the speed, choosing the optimal one for this particular log or this batch of boards? We'll have to put a gearbox or variator. But the gearbox switches speeds in steps, and everything needs to be stopped for this, and the variator is too capricious ... So people came up with a device that can negotiate with an asynchronous motor and, in exchange for making its life easier, get the ability to smoothly control the speed and at the same time also reduce electricity consumption. In dry technical terms, a frequency converter gives us the following main advantages:

operational automatic or manual control of the speed or a parameter that depends on this speed;

energy savings when replacing other control methods;

reduction of starting currents to the minimum required for the implementation of the start;

reduction of shock loads on the mechanism during start-up;

comprehensive protection of the engine and mechanism.

This is not a complete list of the functions of the frequency converter, but even the listed properties make it possible to provide an order of magnitude better controllability of the equipment and a significant increase in its service life. However, for all these tempting opportunities, you will have to pay a rather large amount, and I really do not want to be mistaken in choosing a model that will solve your problems. Let's try to figure it out with this choice. Actually, buying a converter is no more difficult than buying a car, that is, most likely, your new car will drive, but how quickly, comfortably and for a long time is a question.

So, let's assume that we already have the engine. When choosing a converter, most users rely on the motor power. As a rule, the powers of the motor and the converter are the same, however, there are motors (for example, the VASO series), the rated current of which significantly exceeds the standard value for a given power. Without going into the details of the design of asynchronous machines, we only note that the required power of the converter can be significantly higher than the rated power of the motor, and since the limiting factor during the operation of the converter is its rated current, you need to choose a model whose rated current is not lower than the rated current of your motor.

The second question is the nature of the load. If the motor is loaded with a circulation pump or fan, then the load torque is proportional to the square of the speed. This load is even called "pumping" and is the lightest option for the engine. Any load that differs from this, in the first approximation, can be considered independent of speed. Many manufacturers make a series of transducers specifically for pumps, and they tend to be cheaper. Other companies allow the use of standard models with larger pumps, which also turns out to be more profitable.

Another significant point is engine overloads (continuing the analogy with choosing a car, do you prefer a relaxed or sporty type of driving?). Pumps and fans have practically no overloads, but for other mechanisms this issue is very important. The overload capacity of different models of frequency converters can vary greatly. Therefore, to select a converter, you need to know the nature of the overloads of your particular mechanism, in particular: what is the level of overloads, what is their duration and how often they appear.

Now we will decide in which range we will regulate the speed. If the speed does not drop below 10% of the nominal, then almost any converter will do, but if you need to reduce the speed further, while ensuring the rated torque on the shaft, you need to obtain from the manufacturer confirmation of the converter's ability to ensure that the motor operates at frequencies close to zero. In addition, there is another issue related to the speed control range that needs to be addressed - engine cooling. The fact is that usually an asynchronous motor is cooled by a fan attached to its shaft, therefore, when the speed decreases, the cooling efficiency drops sharply. If the motor will operate at low frequencies for a long time, then it is necessary to provide independent cooling, in other words, install a fan with independent power supply. The exact recipe for when such a fan is needed and when not, it is impossible to give without special calculations, it all depends on the time of operation at a reduced speed, the magnitude of this speed and the magnitude of the load. With a load with a "pumping" characteristic, a fan is usually not needed, and it is easier to not install it on the conveyor or saw motor at first, but simply measure the temperature of the motor during operation. Roughly speaking, if you cannot keep your hand on the engine, the fan must be installed. By the way, the problem of cooling is a problem of the user, not the manufacturer, so the seller may not tell you anything. However, serious companies warn about this problem.

The third issue that we must consider is inhibition. When the speed decreases, the kinetic energy of the engine and mechanism must be put somewhere. Converters capable of returning this energy to the network are usually significantly more expensive, and without special need, their purchase is hardly justified. If you use coasting braking, similar to the usual disconnection of the motor from the mains, then the energy will go into friction, but the stopping can be quite long. The inverter can stop the motor faster by actively generating heat through its cooling radiators and the motor (is motor braking familiar?). If this is not enough, a special braking unit is required, consisting of a braking unit (sometimes called a “brake chopper” or “chopper”) and an external braking resistor to dissipate the heat. The braking module can be built into the converter as a standard element, and then there will be no need to pay for it separately, it can be built in when ordering for additional money or purchased and connected later if necessary. The latter option is preferable if it is not known whether this module will be needed at all. Unlike a braking unit, a braking resistor is a unified product and can be purchased from both the inverter supplier and third-party manufacturers. If you buy from the same company as the converter, then you can be sure that the resistor will be selected correctly. And if you buy from third parties, you can find a cheaper option. From the author's point of view, when buying two or three converters, the savings will not justify the time spent on searching and the risk of making the wrong choice, but when purchasing large quantities, it is worth spending a little time on calculations and searching in order to get a significant total price reduction.

Having answered these questions, we practically determined the requirements for the power section of the converter (body type, engine power, the number of doors and driving axles selected, now we will deal with the gearbox).

First, let's decide how we will control the speed of the motor. The simplest option is similar to adjusting the volume of a radio receiver: turn the potentiometer knob in one direction - the speed increases, in the other - decreases. Sometimes this potentiometer is even present on the converter. Another option is two buttons: one to increase the speed, the other to decrease it. This type of control is called "automatic potentiometer", it is more convenient because it is impossible to accidentally change the speed of the drive, in addition, buttons in production conditions are usually much more reliable than a variable resistor. The "automatic potentiometer" circuit is implemented on almost any converter.

If the electric drive will be controlled by a controller or other external device, it is necessary to pay attention to whether the control signals of the controller and the converter match. In modern technology, there are actually only two of these signals - 0-10 V and 4-20 mA. If the signal in your system differs from the indicated options, then you need to check with the seller whether the converter offered to you can work with it.

Sometimes it is convenient to maintain different but previously known speed values in different modes by selecting the required value from the converter memory (a kind of cruise control). In this case, the required speeds are determined and stored in memory at the setup stage, and during operation, the operator only selects the desired value with an external switch.

The most "smart" control option is to force the converter to change its speed on its own, maintaining a certain parameter at a given level (pressure at the pump outlet, load of the mechanism, etc.). In this case, you will need a so-called PID controller in the converter and the ability to connect a feedback sensor that measures the current value of the monitored parameter. As a rule, modern converters allow you to implement all these modes, you just need to accurately imagine the desired option and ask the seller whether it is possible to implement it.

In addition to control functions, the inverter is usually assigned engine protection functions (seat belts, airbags). Almost all converters have a wide range of current limiting functions - during start-up, during continuous operation, during stopping and even in the event of a short circuit. This saves the engine from failure in the event of a mechanism malfunction, a jammed rotor or unacceptable wear of the bearings. In addition, many converters have a thermal model of the motor in their control program and are able, based on the results of its operation, to protect the motor from overheating. In other words, the inverter knows what the temperature of the motor is and will not allow it to overheat. If a temperature sensor is installed in the motor, it is advisable to have a corresponding input in the frequency converter for additional motor protection according to the readings of this sensor.

Let's now take a look at the control panel. Usually it consists of a display and a keyboard (there is no steering wheel there ...). In the simplest case, the display shows only numbers showing the parameter number and its value. If the control panel is needed only at the stage of commissioning, then this is enough, although working with such a display is rather inconvenient. Most modern converters have a multi-line alphanumeric display. This allows you to better navigate the converter menu, and with some skill - to do without a cheat sheet in the form of an operation manual. This is especially important if, in the event of an accident, it is necessary to quickly take action: in this situation, it is important to know the cause of the accident, and there is no time to "decipher" the readings. Some converters have a graphic display on which you can display not only the values of the parameters, but also the graph of their changes. Most foreign-made devices do not have the ability to display the Russian language, however, as practice shows, this inconvenience quickly becomes an advantage: the lexicon of messages is not very large, and it is not difficult to remember it, especially remembering the school course of a foreign language, but this protects against excessive curiosity of the staff. By the way, about the protection against unauthorized interference in the operation of the converter (remember the keys to the door and ignition). Most devices have password protection, sometimes separate for control and parameter change. In addition, with some converters, the control panel after adjustment can be simply removed and carried away. If it is supposed to use the remote control for operational control and display of current information, then it is worth asking the seller whether it is possible to take the control panel to the front panel of the cabinet or to another convenient place.

In the process of work, we will also need signaling devices (something like "low oil level" lamps, "open door" on the dashboard of the car and a tedious squeak when reversing). All converters have several discrete outputs, usually relays or open collector outputs, which can inform you of a wide variety of events inside the drive: an alarm, when a set speed is reached, when the converter is ready for operation, etc. Often, each of these outputs is equipped with a timer that delays the moment of switching on or off the corresponding relay, which can also be used when building a control system. Many converters also have analog outputs, to which ordinary ammeters or voltmeters can be connected to show speed, current, voltage, load torque, etc. The same outputs can be used to transfer parameter values to an external controller or other control or recording device.

Now let's think about where and how we will install the converter (this is already similar to finding a garage). If the intended installation site is an electrical cabinet, then in addition to the dimensions, we will be interested in the availability of free space around the device and the volume of air required for cooling. In addition, you need to think about how the heat generated by the converter will be removed, the losses of which can be up to 5% of the converter power. If it is supposed to install the converter separately (on the floor or on the wall), then it is necessary to clarify the degree of its protection. The IP00 version is only acceptable for installation in a cabinet or special room, since there is no protection against electric shock. The IP20 version allows installation in public areas, and when installed in rooms with high humidity or a large amount of dust in the air, it is necessary to use the IP54 version or another in accordance with the requirements of the standards. And one more important aspect related to the installation location of the device: if the output cable between the inverter and the motor exceeds a certain length, then a special choke must be installed. This length is different for different cables, different currents and different converters, so tell the seller the distance from the place where the converter is supposed to be installed to the motor, and he will tell you if you need an output choke in your case.

We have discussed the main parameters. However, modern frequency converters have a number of additional functions that you may find useful. Let's list the most common ones according to their importance (from the point of view of the author).

Work with unstable power supply. A very relevant parameter for Russia (remember our roads?). What is the acceptable supply voltage range? How does the converter behave when the supply voltage changes? In good models, a mains voltage from 380 to 460 V with fluctuations of +/- 10% is permissible. But when the power supply drops or it is completely turned off for a short (and not very) time, the behavior of the converters is very different. It is possible to maintain operability with a proportional drop in speed, automatic restart when power is restored, determine the speed of the motor when restarting (so as not to start acceleration from zero), and even a function of controlled soft stop of the motor in case of complete (!) No power supply. All of these functions have a large number of programmable parameters that allow you to set exactly the algorithm of operation that will lead to the least loss in case of network problems.

Serial communication means. More and more often it is required either to immediately include the electric drive in the automated control system, or to provide for such a possibility in the future. A serial communication port, usually of the RS485 standard, is used for this purpose. The exchange standard and protocol must be clarified upon purchase, as well as the possibility of purchasing a serial communication unit or replacing it with a unit of another standard in the future. It is better to leave these approvals at the mercy of those specialists who are engaged in the automation of technological processes. But even if your enterprise does not have a centralized control system, through such a port you can connect the inverter to a computer, which will greatly simplify setup. Now there are manufacturers whose equipment, with such a connection, allows for remote configuration, management and control via the Internet from anywhere in the world: whether it is a neighboring office or the manufacturer's service department.

The ability to prohibit operation at certain frequencies. This function is relevant if, at certain speeds, resonance phenomena are observed in the mechanism, in other words, if at the same time the installation starts to move and threatens to collapse. True, until you have a converter, it is impossible to find out whether there will be such problems, and when it appears, it will be too late to change anything. Therefore, it is better to have the ability to block operation at certain frequencies.

Automatic matching procedure with the engine. In the simplest converters, there is no coordination: the converter outputs a voltage of a certain frequency and amplitude at the output, and it is not very interested in the parameters of the motor windings. More modern models require a number of additional parameters to be entered, which must be searched for in reference books. Transducers of the latest generations either use the so-called identification start, in which the transducer measures all parameters by itself, or take measurements directly during operation. In the latter case, this happens unnoticed by the user. You should pay attention to this function only if your drive is very complex and responsible.

Management principle. Three types of control can be distinguished - U / F control (regulation of the ratio of voltage to frequency), vector field control and direct torque control (indicated in ascending order of "cleverness" and price). It is difficult to draw a clear line between them now; the manufacturer often uses various types of controls in his converter. In the vast majority of applications, the first two types of control are sufficient, but with very different loads and large overloads, it may be necessary to directly control the torque. If your staff does not have an electric drive engineer, then it is better to consult with the seller to resolve this issue.

The ability to use multiple sets of parameters. This function allows you to configure the converter for two or more modes of operation and switch between them using a toggle switch or other external signal. This can be helpful if you plan to use the device with different motors, under different loads, under different conditions, etc.

Not even half of the possible additional functions are listed here. If you have any exotic wishes (watching TV during operation, heating a kettle on a braking resistor, etc.), do not hesitate to ask - what if someone has these functions!

Despite the somewhat humorous tone of this article, the choice should be taken very seriously. You shouldn't overestimate your requirements, but you don't need to give up the necessary functions either. Remember that all features will have to be paid for. We deliberately did not touch upon the issues of equipment reliability here, since everyone usually decides this issue for himself, and you can argue about the reliability of the products of this or that manufacturer indefinitely ... The author can only wish you success in your choice, and the chosen converter - long life.

Ruslan KHUSAINOV, Technical Director, Santerno CJSC

A frequency converter is used in conjunction with an asynchronous motor, automatically converting the AC frequency to the required parameters. Thus, the device monitors the speed and torque of the electric motors in a continuous process. Using an electrical device, you can not only fully automate production processes, but also achieve significant energy savings - up to 50%.

Modern frequency converters

The market of electrical equipment is represented by frequency converters of a wide range of applications. Devices can be both low-power and high-voltage units. Modern equipment provides continuous process control in systems with asynchronous and synchronous motors.

Frequency control devices are widely used in almost all industries and transport. The bulk of all electricity produced in the world is used to operate electric motors, and the function of controlling their operation is entrusted to frequency converters.

Modern frequency converters are used as controls in the following systems and equipment:

· Conveyor mechanisms;

· Lifting equipment (cranes, elevators);

· Pumps and water purification systems;

· Machine tools for industrial use;

· Fans.

Choosing the right device according to predefined criteria will ensure continuous and stable operation of the drive and reduce energy costs.

Varieties of frequency converters

Depending on the operating conditions, the frequency converter must have the appropriate technical characteristics and the proper level of protection. So, in the simplest case, a device with a degree of protection IP 20 has a standard housing that reliably protects against moisture and dust. The chemical and mining industry requires the use of IP 54 and IP 65 devices. The modular architecture of frequency converters allows you to customize the device for individual conditions and take advantage of additional options.

For asynchronous electric motors

Asynchronous power units occupy a leading position in terms of the degree of use in industry and everyday life. In view of their design features, these drives have their own drawbacks, to eliminate which, in fact, a speed control device was created. A correctly selected frequency controller can reduce the starting current by almost 80% and achieve smooth regulation of the rotor rotation process.

For fans

The frequency converter in ventilation systems is of primary importance. Thanks to it, the fan speed and rotation frequency is changed smoothly and continuously. Stable and automatic adjustment of the equipment operation is configured based on predetermined parameters, which usually include air temperature and humidity, concentration of foreign substances, etc. There is an option to set up automatic on / off of the system or its individual units.

Frequency converters for the pump (equipment)

The main working element of modern pumps is an electric motor, the operation of which is regulated by a number of mechanical devices. In the recent past, shut-off and control valves (valves, gate valves, gates) acted as such mechanisms. In modern pumping systems, the fluid flow is controlled using frequency converters. Today, frequency converters can be paired with a pump in the same way as with electric motors, which in turn can extend the life of pumping equipment several times.

Frequency converter capabilities

The functional capabilities of modern chastotniks have been significantly expanded and make it possible to automate the operation of electric drives even in the most difficult conditions.

Unstable voltage operation

Not all electrical networks can provide the connected equipment with a stable power supply. Ideally, modern converters correctly perform their functions in the voltage range of the supply circuit 380-460 V, the permissible deviation is 10%. The models of the frequency workers presented on the catalog page allow you to preserve the performance of the electric motor by means of automatic restart after a short-term power outage (drawdown) with a smooth change in the speed and torque of the motor.

Working at resonant frequencies

The natural resonance frequency of some mechanisms can cause unacceptable vibrations, which are often the reason for the failure of the control system. Thanks to the function of excluding unacceptable frequencies, the operation of the frequency converter becomes safe, and the mechanism itself is protected from possible breakdown.

Network exchange

For the joint operation of the electric motor and the automatic control system, various data transfer protocols are used. The most widespread is the Modbus communication protocol with the RS-485 interface, however, depending on the equipment used, the question of using one or another protocol is specified for each specific case.

The optimal choice of a frequency converter is reduced to the compliance of its functionality with the technical characteristics of the electric motor. On the site of the company "ENERGOPUSK" there is a huge range of electronic control devices, where you can stop at the optimal choice of an electrical device based on the economic feasibility of purchase and operation.

Frequency converter power

Power is one of the most basic parameters of an electric drive. When choosing a frequency converter, first of all, it should be determined with its load capacity. In accordance with the available nominal motor power, a frequency converter is selected, designed for the same power. And such a choice will be correct, provided that the load on the shaft does not change dynamically, the current does not significantly exceed the nominal set value, both for this motor and for the frequency distribution device. Therefore, it would be more correct to make a choice based on the maximum value of the current consumed by the electric motor from the CP, taking into account the overload capacity of the latter. Typically, the overload capacity is indicated as a percentage of the rated current, together with the maximum allowable time for the overload to last before activating the direct protection. Thus, for the correct choice, you need to know the nature of the overloads of your particular mechanism, in particular: what is the level of overloads, what is their duration and how often they appear.

Mains voltage for frequency converter

Equally important is the question of the supply voltage. The most common case is power supply from a 380V three-phase industrial network, but options are possible when the drive is designed to operate from a 220-240V single-phase network. As a rule, the latter is limited to a number of capacities up to 3.7 kW. There are options for a high-voltage drive, which make it possible to control more powerful motors, with powers already measured in MW, at relatively lower current values.

Each of the options is applicable for different kinds of solutions, and depends both on the possibilities of power supply and on a number of possibilities due to the use of the corresponding drive.

Frequency converter regulation range

If the speed does not fall below 10% of the nominal, then almost any frequency converter will do, but if you need to reduce the speed further, while ensuring the rated torque on the shaft, you need to make sure that the motor frequency converter is able to operate at frequencies close to zero. In addition, there is another issue related to the speed control range that needs to be addressed - the cooling of the electric motor. Usually, an asynchronous electric motor (self-ventilated) is cooled by a fan mounted on its shaft, therefore, when the speed decreases, the cooling efficiency drops sharply.

Some electronic devices for changing the frequency are equipped with a thermal control function using feedback through a temperature sensor installed on the motor itself. There are other options for solving this issue, but without using this device.

The need for a braking mode of the frequency converter

Coasting braking (inertial braking) is similar to disconnecting the motor from the mains, and the process can take a long time. Especially if these are highly inertial mechanisms. With the help of the frequency distribution of the electrical impulse, it is possible to stop or brake with a transition to a lower operating speed in a shorter period of time. Several options are possible:

supply electricity to the network (regenerative braking mode);
to stop by applying a voltage of a lower frequency or constant voltage to the stator windings, then the excess of the stored kinetic energy will be released in the form of heat through the radiators that convert electricity and the motor itself (DC braking mode);
stop or brake using a brake chopper and brake resistor kit

The feasibility of using a particular method is considered mainly from the point of view of economic benefits. So recuperation into the network is more profitable in terms of energy savings, a drive using a braking resistor is a cheaper technical solution, engine braking does not require additional costs at all, but in turn is possible only at low powers.

Frequency converters as a way to control an electric motor

Some mechanisms can be controlled from a reference signal under conditions of a smooth change in speed, and in some cases operation at fixed speeds is required. Moreover, in both cases, it is possible to control both from the control panel of the PE, and from the use of the terminals of the control circuits of the electronic device, smoothly lowering or increasing the current, buttons, switches and potentiometers.

When implementing the latter option, you must make sure that there is a sufficient number of required inputs. In the case of using an external control device (controller, logic relay, etc.), it is necessary to ensure that the technical parameters are matched. Usually these are current or volt signals with ranges of 0% u202620mA, 4% u202620mA and 0% u202610V, respectively. If the drive is controlled over a network, then an appropriate interface and support for the appropriate communication protocol are required.

Motor control can take place automatically, for this you need a PID controller and the ability to organize feedback from the sensor of the controlled parameter

Display of drive parameters

Basically, any frequency changer has a panel with a display and the necessary controls for commissioning and control. The same display during operation can be used to display any parameters.

Displays can differ in the number of lines, which means information content, the type of the display itself (seven-segment display or liquid crystal). If it is impossible during operation to observe the parameters on the display of the electric drive itself, using analog and discrete (relay, transistor) outputs, you can display the necessary information on the remote control.

In addition to displaying parameters (states "operation", "failure", "braking mode", value of load current, engine speed, frequency and voltage of the supply network, etc.), some devices have the ability to generate control signals through the same analog and discrete outputs, so the most to implement more complex control systems.

Protection functions

In addition to control functions, the electronic frequency changing device is usually assigned protection functions. As a rule, the main set are:

current limiting at start, during continuous operation, at stop and short circuit;
overvoltage and undervoltage protection;
engine temperature control;
protection against overheating of the radiator;
output IGBT protection.

Installation and installation of the frequency converter

An important point is the choice of the proposed installation site for the frequency converter, and hence the conditions for its operation:

current limiting at start, during continuous operation, at stop and short circuit
Operating temperature range
humidity
altitude
vibrations
degree of protection (IP)

In some cases, compactness is a decisive factor at the selection stage. What are the dimensions of the drive to be installed and how to install it? Is it possible to move the radiators of the power section of the emergency room to the rear, providing sufficient ventilation with a smaller cabinet?

Information about environmental conditions is an integral part of the technical specifications when choosing a frequency converter, and failure to comply with them during installation can lead to its failure. During the installation process, many questions arise, but these are some of the first that you have to face.

Functionality

Modern electric drives have many functionalities. Let's list the frequently encountered ones according to their importance.

Work with unstable power supply.

This is a relevant parameter especially when used in Russia. Hence the question: "What is the permissible supply voltage range?" A good range of supply voltage for modern frequency converters is 380-460 V with a deviation of ± 10%. It is necessary to clarify what is the action of the frequency converter in the event of a drawdown or a complete power outage for a short or very short time?

Is it possible to maintain performance with a proportional change in speed, motor torque, automatic restart after power recovery, pick up the speed of a running motor when restarting after a power failure, etc. If the available functionality provides an acceptable mode of operation of the mechanism while maintaining its operable state, then we can assume that the issue of unstable power supply has been removed for you, otherwise it is worth either solving the issue of power supply, or thinking about choosing other equipment.

Elimination of operation at resonant frequencies.

Some mechanisms have their own resonant frequencies when operating at which unacceptable vibrations are observed, which can lead to equipment damage. In such cases, the function of excluding unacceptable frequencies in the converter will protect the mechanism from its premature failure.

Network exchange.

Usually it is required either to include the drive in an automatic control system, or to foresee the prospect of such use of systems for changing the frequency of electric current in the future. To do this, you need to understand the standard and communication protocol.

Currently, there is a wide variety of them, which makes it possible to make the work in the ACS mode most optimal. They can differ in distance, the number of connected objects and noise immunity.

The most common version of% u2013 is the RS-485 interface and the Modbus data transfer protocol, but in order to coordinate the work as part of an automatic control system, this issue should be clarified in more detail with the supplier or the manufacturer.

Automatic tuning.

To date, the choice of electric drives is quite large, but there are still the simplest models in which tuning for the parameters of the engine, or rather its windings, is not performed. Later models require a number of additional reference data to be entered.

Frequency converters have the ability to carry out the so-called identification start (autotuning mode), in which the winding parameters are determined automatically even before starting, or already with a rotating motor. If it is intended to implement a precision control system on the selected drive, then this issue is especially relevant.

CP management principle .

The most common variable frequency drive based on asynchronous squirrel-cage motors uses scalar and vector control.

Scalar control is based on the principle of constancy of the ratio of the output voltage of the frequency converter to its output frequency. That is, when the frequency changes, the voltage amplitude changes in such a way that the ratio of the maximum torque of the electric motor to the current moment of the load remains unchanged. This ratio is called the overload capacity of the electric motor.

An important advantage of the scalar method is the ability to simultaneously control a group of electrical machines. Scalar control is applicable for most practical applications of a frequency drive with a speed control range of up to 1:40 .

Vector control, in turn, can significantly increase the accuracy of maintaining the output frequency, the accuracy of speed control, as well as the accuracy of maintaining the torque. Also, a distinctive feature of vector control is the ability to control the torque on the motor shaft when it operates at frequencies close to zero. The ability to use multiple sets of parameters. The latest generation of converters has the functionality to select various combinations of settings for several modes of operation of the same electromechanical converter or for several with different technical parameters.

The number of functions described above is a small part of their huge set, already counted in hundreds in the latest generation equipment. You need to choose the necessary ones based on those requirements that dictate the intended areas of their application. It is unlikely that the stage of selecting a frequency converter is limited to solving the above issues, but these are the ones that you have to face at the initial stage.

The choice of a chastotnik as a high-tech equipment is not simple in itself and ultimately comes down to the economic feasibility of purchasing and using it. Hence, you should not overestimate the requirements and thereby overpay for unused options, and at the same time abandon the necessary ones, in the hope of making the mechanism, drive and system as a whole operational.