Frequency converter: the principle of operation. High-voltage frequency converter

Frequency converters are devices that are capable of changing the frequency of an electric current. These devices are most often connected to asynchronous motors. Their main task is to regulate their capacity. Depending on the design features, single-stage and two-stage converters are distinguished.

Also, the devices are divided according to the control method. In particular, there are scalar and vector modifications. In order to understand the devices in more detail, the standard converter circuit should be considered.

Converter circuit

The usual frequency converter 220-380 V consists of a relay, as well as a modulator for changing the clock frequency. Resistors in devices are used most often of a selective type. It is also important to note that the models are equipped with transceivers. There are pins for connecting the device. Regulators are most often installed on the control unit. Some modifications use an expander. It should also be noted that various types of insulators are installed to ensure safe operation of the device.

Single-stage modifications

Tetrodes are installed on each single-stage frequency converter. The working principle of the models is based on changing the phase frequency. First of all, the voltage will fall on the relay. Then the current is passed through the transceiver. To reduce the sensitivity, thyristors are used. Immediately the conversion process takes place in the modulator.

It is also important to note that some models have filters. They help to cope with electromagnetic interference. Single-stage converters are used, as a rule, for compressors. In some cases, they are installed on pumps. The rated voltage of the device is maintained at 220 V. The operating current is on the average 3A. The accuracy of the stabilization of the speed of the models is different. The error of the frequency converter most often arises from overload in the network.

Two-stage models

Triggers are installed only on a two-stage frequency converter. The principle of the models is based on the change in the phase frequency in the circuit. Unlike the previous type, the current conversion begins in a thyristor block. Before this, the rectification process is carried out. At this stage, the limiting frequency is reduced to a level of 45 Hz.

The rated voltage of the device is rated at 320 V. In turn, the working current indicator does not exceed 5A. For some modifications, the resistors are of a selective type. Modulators in this case are installed with regulators. Direct connection of the transducers is via the contacts that are on the rear panel. Two-stage devices are used for various machines and drives.

Low-voltage modifications

Low-voltage models are made on the basis of diode rectifiers. As a rule, devices are made compact, and the nominal voltage does not exceed 120 V. The working current parameter varies in the region of 2 A. For powerful asynchronous motors, these devices are not suitable. Most often they are used on compressors. Tetrodes in this case are available with insulators.

Some models have filters installed. Regulators are used with or without an amplifier. It is also important to note that there are modifications with resonance resistors. The nominal input voltage parameter is an average of 130 V. However, the system current overloads are small.

High-voltage modifications

A high-voltage frequency converter is used for asynchronous motors of 10 kW or more. Rectifiers in many devices are installed with a thyristor block. Resistors are most often used selective type. To date, you can find a high-voltage frequency converter with two relays. Current overloads such systems withstand large. It is also important to note that filters are installed in the devices to deal with interference. Thus, the accuracy of speed stabilization is high.

Scalar devices

Scalar converters are controlled only by modulators. In this case, you can install the remote control to remotely change the engine power. Most often on the market are offered single-stage scalar modifications. Resistors in them are used in different types. As a rule, models are sold with one relay. Rectifiers for scalar modifications are rare. Expanders for short-wave interference are installed with insulators.

Some modifications use trigger blocks. Such converters are well suited for high-power compressors. Speaking about the parameters, it is important to note that the nominal voltage at them fluctuates around 220 V at a frequency of 60 Hz. The overload system is maximum capable of withstanding 5 V. The accuracy of the stabilization models differ. On average, this parameter does not exceed 3%.

Models of vector type

Vector converters are controlled by means of regulators. In this case, it is not possible to connect the console. The devices are most often of a two-stage type. For powerful asynchronous motors, these converters are suitable. It is also important to note that they use knob and rotary type controls. Resistors are installed with insulators and are able to withstand a large input voltage. Most often, the modifications are sold with two relays. It is also important to mention that some converters have a thyristor block. Filters are only of a wired type. To combat impulse noise isolators are found.

Devices for 5 kW asynchronous motors

Frequency converters for asynchronous motors are often installed on machines . The principle of operation of devices is based on a phase change in frequency. Converters for asynchronous motors of 5 kW are produced only of a single-stage type. The modulators used in the models are usually dipole ones. In some modifications, thyristor blocks are installed. It is also important to note that there are many models with expanders on the market. All this makes it possible to change the engine power very quickly.

Triggers are most often used in a two-bit type. In turn, thyristors can only be used for expansion. In many converters, the rated current does not exceed 230 V. The device overloads are maintained at 20 V. The nominal current parameter is 3 A. However, in this case much depends on the conductivity of the modulator.

Modifications for 10 kW engines

On the compressors and conveyors are often installed frequency converters for asynchronous motors. The principle of operation of devices is based on a phase change in frequency. Models are produced, as a rule, of a two-stage type. In some of them, the resistors are set to resonance type. Contacts are used to connect the inverter. Modulators are only of a dipole type. Transceivers in the device are distinguished by increased sensitivity.

Overloads, they are able to withstand a maximum of 20 V. The nominal voltage indicator fluctuates around 230 V. Modifications with two relays are rare. Many transducers use transceivers of chromatic type. It is also important to mention that devices with regulators are on the market. Amplifiers are used to increase the stabilization of the system. Trigger blocks, as a rule, are absent in converters of this type. The nominal current parameter in the devices does not exceed 3.5 A.

Devices for submersible pumps

The frequency converter for a submersible pump is manufactured with a dipole modulator. Most often in the market are single-stage devices. The principle of their operation is based on a phase change in the clock frequency. The overload parameter for the models does not exceed 15 V. In turn, the working current indicator on the average is 4 A. Some modifications use selective resistors.

Thyristors for the frequency converter for the pump are installed with insulators. Expanders are used to combat impulse noise. Most often converters can be found with one relay. In some cases, devices that have a chromatic transceiver come across. These models are able to boast a high stability of work.

Modification of "KVT-1"

Frequency converters "KVT-1" are used for drilling machines. In this case, the modulator is of a dipole type. It is also important to mention that this single-stage converter can be controlled from the console. A selective resistor is available with an increased conductivity parameter. The transceiver block for this 220 V frequency converter (3-phase output) is installed near the modulator.

Directly lowering the clock frequency is carried out due to the rectifier. The expander is not available for this model. Speaking about the parameters, it is important to mention that the rated voltage is 220 V, and the system can withstand a maximum of 12 V. The operating current of the converter does not exceed 3 A. The stabilization accuracy is about 2%.

Devices for conveyors with their own hands

For the conveyor to make a frequency converter with their own hands is quite simple. In this case, you should first choose a relay for the device. The nominal input voltage it is required to withstand in 220 V. The resistor for the converter will need a selective type. Total transceivers need to prepare three. One of them must stay on the modulator to stabilize the control process. The remaining transceivers are installed near the contacts.

A modulator for the model will require a dipole type. However, before that it is important to install a rectifier. Most often it is selected with conductivity at a level of 3 microns. Expanders are used both as an analogue and as a switch type. To combat interference, you need a filter. The expander of the model will have to be used with insulators. The operating current in the system should not exceed 3 A. As a result, one can hope for the accuracy of stabilization in the region of 2%.

Models for mixers with their own hands

For a mixer, it is possible to assemble a frequency converter with your own hands only on the basis of an expansion thyristor. In this case, one relay is required. The modulator is most often selected by the dipole type. The nominal input voltage it is required to withstand in the region of 220 V. The transceiver is used only of the chromatic type. Before installing it, it is important to solder the resistor near the contacts. Radiation tetrodes are used to control the power of engines. At the end of the job, it only remains to check the operating current in the system. On average, the accuracy of power stabilization should be 3%.

The device "KVT-2"

"KVT-2" is a powerful single-stage frequency converter. The principle of the device is based on the phase change of frequency. For this, a dipole modulator is installed, which is connected to resistors of high current conductivity. The transceiver is in this case installed in a chromatic type. There are two thyristors in the circuit. To increase the accuracy of stabilization, this single-phase frequency converter has an amplifier. The trigger in the present device is located with insulators. The relay has one model installed.

Arrangements for reciprocating compressors

For piston compressors, a two-stage frequency converter is most often selected. The principle of the device is based on the phase change of frequency. Many models use two-bit type triggers. Thyristors in converters have a current conductivity of 2 microns. The nominal voltage is 230 V on average. The operating current in the system is maintained at 3A.

Tetrodes in devices are used with insulators. It is also important to note that the market presents two-stage modifications. The nominal voltage rating reaches up to 320 V. The system can withstand overloads of 30 V. The accuracy of power stabilization in the models is not high. Expanders are often used in a switched type. The models are connected directly via the contacts on the rear panel of the device.