The rotor of an electric motor begins its rotation using electromagnetic forces from the rotating magnetic field caused by the armature winding. The number of revolutions is determined by the frequency of the current in the network. The standard current frequency is 50 hertz. This means that 50 periods of oscillation occur in 1 second. The number of vibrations per minute will be 50 x 60 = 3000. This means that the rotor will rotate 3000 rpm.
If you learn to change the frequency of the current, you will be able to adjust the speed of the motor. It is on this principle that frequency converters operate.
The modern design of frequency converters looks like a high-tech device consisting of semiconductor devices, together with a microcontroller of an electronic system. With the help of this control system, important parameters are changed, for example, the number of revolutions.
You can change the drive speed using a gear-type mechanical reducer, or based on a variator. But such mechanisms have a bulky design and need to be maintained. Using a frequency converter (inverter) reduces maintenance costs and increases the functionality of the mechanism drive.
Kinds
According to their design features, frequency converters are divided into:
- Induction.
- Electronic.
Asynchronous electric motors with a wound rotor connected to generator mode are similar to an induction frequency converter. They have low efficiency and efficiency. In this regard, these types of converters have not found popularity in use.
Electronic types of frequency converters make it possible to smoothly change the speed of electric motors.
In this case, two possible control principles are implemented:
- According to a certain dependence of speed on current frequency.
- According to the vector control method.
The first principle is the simplest, but not perfect. The second principle is used to accurately change engine speed.
Design features
Rice. 1Frequency converters contain the following main modules:
- Rectifier.
- Voltage filter.
- Inverter unit.
- Microprocessor system.
All modules are interconnected. The action of the output stage (inverter) is controlled by a control unit, with the help of which the properties of the alternating current change. The frequency converter for an electric motor has its own characteristics. It includes several protections, which are controlled by a microcontroller. For example, the temperature of semiconductors is checked, and protection against overcurrent and short circuits operates. The frequency generator is connected to the power supply through protection devices. A magnetic starter is not needed to start the electric motor.
Rectifier
This is the first module through which current flows. It converts alternating current into direct current, thanks to semiconductor diodes. A special feature of the frequency generator is the ability to power it from a single-phase network. The difference in design lies in the different types of rectifiers.
If we are talking about a single-phase frequency converter for a motor, then we need to use four diodes in the rectifier in a bridge circuit. For three-phase power supply, a circuit of six diodes is selected. The result is rectification of alternating current, two poles appear: plus and minus.
Voltage filter
A direct voltage comes out of the rectifier, which has significant ripples borrowed from the alternating current. To smooth them out, elements such as an electrolytic capacitor and an inductor are used.
The coil has many turns and has reactance. This makes it possible to smooth out current pulses. A capacitor connected to two poles has interesting characteristics. When a direct current passes, by virtue of Kirgoff’s law it must be replaced by a break, as if there was nothing between the poles. When passing alternating current, it must be a conductor, that is, have no resistance. As a result, the AC portion short-circuits and disappears.
Inverter module
This is the most important component in a frequency converter. It changes the output current parameters and consists of six transistors. Two transistors are connected for each phase. The inverter stage uses modern IGBT transistors.
If you make frequency converters with your own hands, then you need to select design elements based on power consumption. Therefore, you need to immediately determine the type of electric motor that will be powered by the frequency converter.
Microprocessor system
In a homemade design, it will not be possible to achieve such parameters as those found in factory models, since it is difficult to make a control module at home. It's not a matter of soldering parts, but of creating a program for a microcontroller. A simple way is to make a control unit that can be used to regulate engine speed, reverse, and protect the engine from overheating and overcurrent.
To change the motor speed, you need to use a variable resistance connected to the microcontroller input. This device sends a signal to a microcircuit, which analyzes the voltage change and compares it with the standard (5 volts). The system operates according to an algorithm that is created before the creation of the program begins. It is operated by a microprocessor system.
Siemens control modules have become very popular. Frequency converters from this company are reliable and can be used for any electric motors.
Operating principle
The basis of the inverter's operation is a double change in the shape of the electric current.
The voltage is supplied to a rectification unit with powerful diodes. They remove harmonic vibrations, but leave signal pulses. To remove them, a capacitor and an inductor are connected to form a filter that stabilizes the voltage waveform.
Next, the signal goes to the frequency converter. It consists of six powerful transistors with diodes that protect against voltage breakdown. Previously, thyristors were used for such purposes, but they did not have such speed and created interference.
To enable the motor slowdown mode, a control transistor with a resistor is installed in the circuit, which dissipates energy. This method makes it possible to remove the voltage generated by the engine in order to protect the filter capacitors from failure due to overcharging.
The vector-type frequency control method of the inverter makes it possible to create a circuit that automatically regulates the signal. For this, a control system is used:
- Amplitude.
- Pulse width.
Amplitude control works by changing the input voltage, and - the order of action of switching transistors at a constant voltage at the input.
When regulating PWM, a modulation period is formed when the armature winding is connected in turn to the terminals of the rectifier. Since the clock frequency of the generator is high and is in the range of 2-15 kilohertz, the voltage in the winding of the motor, which has inductance, is smoothed to a normal sinusoid.
The principle of connecting keys with transistors
Each of the transistors is connected in an anti-parallel circuit to the diode (Fig. 1). The active current of the electric motor flows through the transistor circuit, the reactive part goes to the diodes.
To eliminate the influence of interference on the operation of the inverter and electric motor, a filter is connected to the circuit, which removes:
- Radio interference.
- Interference from electrical equipment.
The controller signals their formation; to reduce interference, shielded wires are used from the motor to the inverter output.
To optimize the accuracy of operation of asynchronous motors, the following are connected to the inverter control circuit:
- Entering a connection.
- Controller.
- Memory card.
- Program.
- Display.
- Brake chopper with filter.
- Cooling the circuit with a fan.
- Warming up the engine.
Connection diagrams
Frequency converters are used to operate in 1-phase and 3-phase networks. But if industrial power supplies with 220 volts DC are available, then inverters can also be connected to them.
Frequency converters for a 3-phase network are designed for 380 volts, they are supplied to the motor. 1-phase frequency generators operate from a 220 volt network and produce 3 phases at the output. The frequency generator can be connected to the electric motor according to the diagram.
The motor windings are connected in a “star” for a frequency generator operating on three phases of 380 volts.
The motor windings are connected in a delta when the inverter is powered from a 1-phase network.
When choosing a method for connecting an electric motor to a frequency generator, it is necessary to determine the power that the engine creates in different modes, including slow mode and difficult starting. The frequency converter must not be operated with overload for a long time. Its power should be in reserve, then the operation will be accident-free, and the service life will be extended.
Application
Frequency converters are used in devices that require motor speed control.
- Pump drives. Reduces heat and water loss by 10%. Reduces the number of accidents, protects electric motors.
- Ventilation systems. The savings are greater than when working with pumps, since powerful unit drives are used to start powerful fans. Savings come from reducing idle losses.
- Transporters. Inverters adapt the motor speed to the speed of the process system, which is constantly changing. Soft start increases the service life of the system drive, since there are no shock loads that harm the equipment.
- Compressors.
- Smoke exhausters.
- Centrifuges.
- Elevator equipment.
- Woodworking equipment.
- Robotics.
Advantages
- Smoothing of engine operation when starting and braking.
- Ability to control a group of engines.
- Smooth control of the speed of electric motors, without the use of gearboxes and other mechanical systems. This allows you to simplify management, make it cheaper and more reliable.
- Used in conjunction with asynchronous motors to replace DC drives.
- Development of multifunctional drive control systems.
- Change settings directly while working, without stopping.
AC frequency converters have been used for many years in the construction of electromechanical devices and units. They allow you to modulate the frequency in order to regulate the rotation speed of the electric motor.
Frequency generators made it possible to connect a three-phase electric motor to a single-phase power supply without losing power. With the old type of connection, through a capacitive capacitor, most of the engine power was lost, the efficiency was significantly reduced, and the windings of the electric motor overheated greatly.
All these problems were avoided by using a frequency converter. In this case, it is very important to observe the correct attitude towards the electric motor.
Some features of connecting any frequency generator in conjunction with an electric motor.
Firstly
For reasons of safe operation of the device, when connecting a frequency generator (or any other device) to the power supply, it is imperative to install a circuit breaker. The machine is installed in front of the frequency switch.
Moreover, if the frequency converter is connected to a network with three-phase voltage, then it is necessary to install a machine that is also three-phase, but with a common shutdown lever.
This will allow you to turn off power from all phases simultaneously if there is a short circuit or severe overload on at least one phase.
If the frequency converter is connected to a network with single-phase voltage, then a single-phase machine is used. But at the same time, the current of one phase is taken into account, multiplied by three.
When connecting a three-phase machine, its operating current is determined by the current of one phase.
It is definitely forbidden to install a circuit breaker into the neutral cable gap, both with a single-phase connection and with a three-phase one. Such a connection only looks identical in appearance (it is a mistake to understand that there is only one circuit and it does not matter where it is broken).
In fact, if the phase cables break, when the machine is triggered, the power is completely turned off and there will be no phases on the device circuits at all. It is safe. And when the machine with a broken zero is triggered, the operation of the device will stop. But at the same time, the motor windings and frequency circuits will remain energized, which is a violation of safety regulations and is dangerous for humans.
Also, under no circumstances does the grounding cable break. Like the zero, they must be connected to the corresponding buses directly.
Secondly
The phase outputs of the frequency converter should be connected to the contacts of the electric motor. In this case, the windings of the electric motor should be connected according to the “triangle” or “star” principle. The type is selected based on the voltage that the frequency generator produces. As a rule, each inverter comes with instructions that describe in detail how the motor windings are connected to connect a specific frequency drive. The connection diagram of the frequency converter to a 3-phase motor should also be given in the instructions.
Typically, both voltage values are shown on motor housings. If the frequency driver corresponds to the smaller one, then the windings are connected according to the triangle principle. In other cases, according to the star principle. The connection diagram for the frequency converter should also be given in the frequency converter's passport. Connection recommendations are also usually given there.
Third
Almost every frequency converter is supplied with an external one. Despite the fact that the frequency transmitter itself already has an interface for entering control and programming data, the presence of a remote control panel is a very convenient option.
The remote control is mounted in the place where it is most convenient to work with it. In some cases, when the frequency converter is somewhat inferior in dust and moisture protection, the frequency converter itself can be installed away from the engine, and the control panel nearby, so as not to run to the control cabinet and adjust the speed there.
It all depends on the specific circumstances and production requirements.
First start-up and configuration of the frequency converter
After connecting the control panel to the frequency converter, the motor shaft rotation speed handle should be moved to the lowest position. After this, you need to turn on the machine, thereby supplying power to the frequency converter. As a rule, after turning on the power, the light indicators on the frequency converter should light up and, if there is an LED panel, the starting values should be displayed on it.
The principle of connecting control circuits of a frequency converter is not universal. It is necessary to follow the instructions specified in the instructions for a specific frequency device.
To start the engine for the first time, you will need to briefly press the start button on the frequency converter. Typically, this button is programmed to start the engine by default at the factory.
After starting, the motor shaft should begin to rotate slowly. It is possible that the engine will rotate in the opposite direction, which is different. From the necessary. The problem can be solved by programming the frequency switch to reverse the movement of the shaft. All modern frequency converter models support this function. You can also use a primitive connection of phases in a different phase order. Although this takes a long time and is not cost-effective in terms of the time and effort of an electrician.
Further adjustment involves setting the desired engine speed. Often, the frequency display does not display the speed of the motor shaft, but the frequency of the voltage supplying the motor, expressed in hertz. Then you will need to use the table to determine the appropriate value of the engine shaft speed.
When installing and servicing, as well as replacing the frequency converter, it is important to follow a number of recommendations.
- Any contact with a hand or other part of the body of a current-carrying element can take away health or life. This is important to remember when doing any work on the control cabinet. When working with the control cabinet, you should turn off the incoming power and make sure that the phases are turned off.
- It is important to remember that some voltage may still remain in the circuit even if the indicator lights go off. Therefore, when working with units up to 7 kW, after turning off the power, it is recommended to wait at least five minutes. And when working with devices over 7 kW, you need to wait at least 15 minutes after turning off the phases. This will allow all capacitors in the circuit to discharge.
- Each frequency converter must have reliable grounding. Grounding is checked according to the rules of preventive maintenance.
- It is strictly prohibited to use a neutral cable as grounding. Grounding is mounted with a separate cable separately from the zero bus. Even if there is a zero bus and a ground bus, if they comply with electrical installation standards, it is prohibited to connect them.
- It is important to remember that the frequency switch off key does not guarantee that the circuits will be de-energized. This key only stops the engine, while a number of circuits may remain energized.
It is carried out using cables whose cross-section corresponds to the characteristics specified in the frequency operator’s passport. Violation of norms to a lesser extent is unacceptable. On the larger side, it may not be advisable.
Before connecting a frequency converter to an electric motor, it is important to ensure that the conditions under which the frequency converter will operate are met. In fact, the conditions must comply with the recommendations given in the instructions.
In each specific case, connecting a frequency generator may be accompanied by a number of mandatory conditions. To find out how to connect a frequency generator to a 3-phase motor circuit, which is available. First, the diagrams are studied. If everything is clear in them, the connection is made by strictly following the instructions. If something is not clear, you should not invent it yourself and rely on your intuition. The supplier or manufacturer should be contacted for appropriate instructions.
It is better to wait for the help of a specialist than to repair broken equipment later. The case will not be guaranteed.
Electric motors, including three-phase asynchronous ones, have become widespread in various fields of activity. The operating cycle of the units is associated with their smooth start and a similar method of stopping. To solve the problem of controlling the frequency of current and motor speed, frequency converters are used.
Purpose and advantages
Electromagnetic forces generated under the influence of the magnetic field created by the armature winding set the rotor in motion. Its rotation occurs at a speed determined by the frequency of the mains current. At a frequency of 50 Hz, 50 oscillations occur within 1 s. Therefore, the rotor rotation speed will be 3000 rpm.
The purpose of frequency converters is to ensure effective motor control by changing current frequency parameters.
The advantages of these devices are:
- ensuring smooth operation of the motor at the time of starting and braking;
- regulation of the operation of engines assembled in a group;
- no need to use gearboxes and other mechanical devices to control engine speed;
- ensuring the operation of drive control systems on a multifunctional basis;
- possibility of adjustments in settings without interrupting the operation of the unit.
Types of devices
Depending on the design features, the main types of frequency converters 220/380 are distinguished - induction and electronic. The first option includes asynchronous types of electric motors, the peculiarity of which is the use of a wound-rotor circuit.
At the same time, they have the ability to operate in generator mode. However, they are not very common in practice, since they have low efficiency and low efficiency.
But the electronic version can be used both in the operation of asynchronous engines and synchronous modifications. Motors are controlled in several fundamentally different ways:
Through scalar control based on linear laws. In this case, the proportional dependence of amplitude on frequency is taken into account. If the frequency changes, the amplitude of the input voltage will also change. As a result, torque, efficiency, and power levels are affected.
Setting the uniformity of the load torque is ensured by a constant ratio of the amplitude to the output frequency. The transforming device forms the specified equilibrium.
With the vector approach, the load torque is constant at any range of frequency changes. This allows for greater control accuracy. The flexibility of the electric drive's response to surges in the output load also increases. The frequency converter for an asynchronous motor provides constant control over the torque.
It is important to remember that the phase of the stator current, which changes under the influence of the magnetic field, is the current vector. It controls the torque. Thus, in this case, an amplitude or pulse width signal control system is used.
Design
There are different types of frequency converters for motors. But at the same time, individual typical blocks can be distinguished constructively. These components are closely related to each other. The control unit determines the operation of the output stage.
In this case, the ability to change the parameters of alternating current plays a decisive role. Additionally, the device includes protection systems controlled by a microcontroller.
The rectifier is the first module. Current flows through it. This is where the alternating current changes. With the help of diodes it is converted to constant. You can choose models for a single-phase network or for three-phase power. The number of diodes in them will differ.
DC voltage with high ripple comes out of the rectifier. To smooth out the ripples, a capacitor and an inductive coil are used. But the process of converting the parameters of the output current occurs in the inverter.
Structurally, it contains transistors. There are 6 of them - a pair for each phase. And the microprocessor system guarantees control of the speed indicators of rotor rotation. All this can be seen in the photo of the frequency converter.
Connection features
Devices designed to control frequency can operate in a single-phase connection or using a three-phase power supply. When operating DC sources that have a voltage of 220 V, they can also be used to connect inverters.
Three-phase type modifications are oriented towards a mains voltage of 380 V. They direct it to the motor. Single-phase inverters are powered from a 220 V network. At the output, they create three phases, which are distributed according to the time parameter.
If you are interested in the question of how to connect a frequency converter, then you can distinguish two circuit diagrams. According to the “star” principle, windings are arranged for the converter, which is powered from a network with a voltage of 380 V. If the connection is to a single-phase 220 V network, then a “triangle” circuit is used.
In this case, the parameter of matching the motor power with the capabilities of the inverter should be taken into account. The converter must not be overloaded. On the contrary, it is advisable to have some power reserve.
At the first stage of connection, a circuit breaker with a rating that matches the operating characteristics of the current consumed by the motor is mounted in front of the device. If the instructions on how to set up the frequency converter have been fully followed, then the phase conductors are connected to the specified motor contacts.
The converting device must be connected to the controller. A connection to the remote control is also required. First check the position of the handle - neutral. Then you need to start the machine. When the process complies with the standards, a light indication is observed.
A slight turn of the handle will activate the rotation of the motor. The reverse button allows you to set the direction of rotation in reverse. To set the desired frequency, adjust the knob. Subsequent operation of the converter will allow more efficient operation of equipment with an electric motor.
Photos of frequency converters
A frequency converter (also known as a frequency converter) is used in electrical engineering to be able to adjust the supply voltage of an electrical machine (3-phase motor) over a wide range.
It is even possible to power a single-phase motor without loss of power. However, this function is present only on devices that do not use capacitors in their circuit.
When connecting a frequency generator, it makes sense to install automatic machines. It is worth noting that switch-off currents must be precisely selected for a specific electrical machine.
For example, if the frequency converter will be mounted on a three-phase motor/generator, it makes sense to install a three-phase machine with a common lever.
In this case, even if a short circuit occurs in one phase, the entire system will be immediately de-energized.
In the case of a single-phase electric motor, it will be quite sufficient to install a single-phase machine, the switch-off currents of which are three times the rated currents of the motor.
Before directly connecting the frequency regulator, you must make sure of the method of switching on the windings of the electrical machine:
- star;
- triangle.
The amount of regulated voltage will directly depend on this. The indicated voltage values are indicated on the body of the electrical machine (on the plate).
If the voltage after the frequency converter corresponds to the lower one shown on the plate, you should change the connection of the windings to the “delta” type. In all other cases, “star” is quite suitable.
It should be understood that the frequency indicator does not reflect the engine speed, but the frequency of the voltage supplying it.
The control panel of the electrical apparatus must be located in a place convenient for the operator. The included instructions will help you understand the main signals of the frequency converter. To start the conversion, you must press the “Run” or “Start” key.
The rotor of any electric motor is driven by forces caused by a rotating electromagnetic field inside the stator winding. Its speed is usually determined by the industrial frequency of the electrical network.
Its standard value of 50 hertz implies fifty oscillation periods within one second. In one minute, their number increases 60 times and amounts to 50x60=3000 revolutions. The rotor rotates the same number of times under the influence of an applied electromagnetic field.
If you change the value of the network frequency applied to the stator, you can adjust the rotation speed of the rotor and the drive connected to it. This principle is the basis for controlling electric motors.
Types of frequency converters
By design, frequency converters are:
1. induction type;
2. electronic.
Asynchronous electric motors, made and launched into generator mode, are representatives of the first type. They have low operating efficiency and are characterized by low efficiency. Therefore, they have not found wide application in production and are used extremely rarely.
The method of electronic frequency conversion allows you to smoothly regulate the speed of both asynchronous and synchronous machines. In this case, one of two control principles can be implemented:
1. according to a predetermined characteristic of the dependence of rotation speed on frequency (V/f);
2. vector control method.
The first method is the simplest and less advanced, and the second is used to accurately control the rotation speeds of critical industrial equipment.
Features of vector control of frequency conversion
The difference between this method is the interaction, the influence of the converter control device on the “spatial vector” of the magnetic flux, rotating with the frequency of the rotor field.
Algorithms for operating converters based on this principle are created in two ways:
1. touchless control;
2. flow control.
The first method is based on assigning a certain dependence of the inverter sequence alternation to pre-prepared algorithms. In this case, the amplitude and frequency of the voltage at the output of the converter are regulated by slip and load current, but without using feedback on the rotor rotation speed.
This method is used when controlling several electric motors connected in parallel to a frequency converter. Flux control involves monitoring the operating currents inside the motor, decomposing them into active and reactive components and making adjustments to the operation of the converter to set the amplitude, frequency and angle for the output voltage vectors.
This allows you to increase the accuracy of the engine and increase the limits of its regulation. The use of flow control expands the capabilities of drives operating at low speeds with large dynamic loads, such as crane lifting devices or industrial winding machines.
The use of vector technology allows dynamic adjustment of rotating torques to be applied.
Substitution scheme
The schematic simplified electrical circuit of an asynchronous motor can be represented as follows.
Voltage u1 is applied to the stator windings, which have active R1 and inductive resistance X1. It, overcoming the resistance of the air gap Xv, is transformed into the rotor winding, causing a current in it that overcomes its resistance.
Vector diagram of equivalent circuit
Its construction helps to understand the processes occurring inside an asynchronous motor.
The stator current energy is divided into two parts:
iµ - flow-forming fraction;
iw is the torque-forming component.
In this case, the rotor has an active resistance R2/s, which depends on slip.
For sensorless control the following are measured:
voltage u1;
current i1.
Based on their values, the following is calculated:
iµ - flow-forming current component;
iw is the torque-forming quantity.
The calculation algorithm has already included an electronic equivalent circuit of an asynchronous motor with current regulators, which takes into account the conditions of saturation of the electromagnetic field and losses of magnetic energy in steel.
Both of these components of the current vectors, differing in angle and amplitude, rotate together with the rotor coordinate system and are converted into a stationary stator orientation system.
According to this principle, the parameters of the frequency converter are adjusted to the load of the asynchronous motor.
Operating principle of frequency converter
This device, also called an inverter, is based on a double change in the signal shape of the supply electrical network.
First, industrial voltage is supplied to a power rectifier unit with powerful diodes, which remove sinusoidal harmonics, but leave signal ripple. To eliminate them, a bank of capacitors with inductance (LC filter) is provided, providing a stable, smooth shape to the rectified voltage.
Then the signal is fed to the input of the frequency converter, which is a three-phase bridge circuit of six IGBT or MOSFET series with reverse polarity breakdown protection diodes. The thyristors previously used for these purposes do not have sufficient speed and operate with great noise.
To enable the engine “braking” mode, a controlled transistor with a powerful resistor that dissipates energy can be installed in the circuit. This technique allows you to remove the voltage generated by the engine to protect the filter capacitors from overcharging and failure.
The method of vector control of the frequency of the converter allows you to create circuits that automatically regulate the signal by ACS systems. For this, a control system is used:
1. amplitude;
2. PWM (pulse width modeling).
The amplitude control method is based on changing the input voltage, and PWM is an algorithm for switching power transistors at a constant input voltage.
With PWM regulation, a signal modulation period is created when the stator winding is connected in strict order to the positive and negative terminals of the rectifier.
Since the clock frequency of the generator is quite high, in the winding of the electric motor, which has inductive reactance, they are smoothed out to a normal sinusoid.
PWM control methods make it possible to eliminate energy losses as much as possible and provide high conversion efficiency due to simultaneous control of frequency and amplitude. They became available thanks to the development of control technologies for power turn-off thyristors of the GTO series or bipolar brands of IGBT transistors with an insulated gate.
The principles of their inclusion for controlling a three-phase motor are shown in the picture.
Each of the six IGBT transistors is connected in an anti-parallel circuit to its own reverse current diode. In this case, the active current of the asynchronous motor passes through the power circuit of each transistor, and its reactive component is directed through the diodes.
To eliminate the influence of external electrical noise on the operation of the inverter and motor, the design of the frequency converter circuit can be included, eliminating:
radio interference;
electrical discharges induced by operating equipment.
Their occurrence is signaled by the controller, and to reduce the impact, shielded wiring is used between the motor and the inverter output terminals.
In order to improve the accuracy of operation of asynchronous motors, the control circuit of frequency converters includes:
input of communication with advanced interface capabilities;
built-in controller;
memory card;
software;
LED information display displaying the main output parameters;
brake chopper and built-in EMC filter;
circuit cooling system based on blowing with long-life fans;
engine warm-up function using direct current and some other features.
Operational connection diagrams
Frequency converters are designed to work with single-phase or three-phase networks. However, if there are industrial DC sources with a voltage of 220 volts, then inverters can also be powered from them.
Three-phase models are designed for a network voltage of 380 volts and supply it to the electric motor. Single-phase inverters are powered by 220 volts and output three phases spaced apart in time.
The connection diagram of the frequency converter to the engine can be made according to the following diagrams:
stars;
triangle.
The motor windings are assembled into a “star” for the converter, powered from a three-phase 380 volt network.
The motor windings are assembled according to the “triangle” scheme when the converter feeding it is connected to a single-phase 220 volt network.
When choosing a method for connecting an electric motor to a frequency converter, you need to pay attention to the ratio of the power that a running motor can create in all modes, including slow, loaded starting, with the capabilities of the inverter.
You cannot constantly overload the frequency converter, and a small reserve of its output power will ensure its long-term and trouble-free operation.
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