Frequency converters are devices that are capable of changing the frequency of electric current. These devices are most often connected to asynchronous motors. Their main task is to regulate their power. Depending on the design features, single-stage and two-stage converters are distinguished.
Also, devices are divided according to the method of control. In particular, there are scalar and vector modifications. In order to understand the devices in more detail, you should consider the standard converter circuit.
Converter circuit
A conventional 220-380 V frequency converter 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 transceivers are installed on the models. There are contacts to connect the device. Regulators are most often installed on the control unit. For some modificationsexpander is used. It should also be noted that various types of insulators are installed for the safe operation of the device.
Single-stage modifications
Tetrodes are installed on each single-stage frequency converter. The principle of operation of the models is based on changing the phase frequency. First of all, the voltage will go to the relay. Next, the current is passed through the transceiver. Thyristors are used to reduce sensitivity. The actual 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 the level of 220 V. The operating current is on average 3A. The models differ in speed stabilization accuracy. Inverter error most often occurs due to network overload.
Two-stage models
Triggers are installed only on a two-stage frequency converter. The principle of operation of the models is based on changing the phase frequency in the circuit. Unlike the previous type, current conversion starts in the thyristor block. Before this, the straightening process is carried out. At this stage, the limit frequency is reduced to 45 Hz.
The rated voltage of the device is maintained at 320 V. In turn, the operating current does not exceed 5A. For some modificationsresistors are of the selective type. Modulators in this case are installed with regulators. The converters are directly connected through the contacts located 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 their rated voltage does not exceed 120 V. The operating current parameter fluctuates around 2 A. These devices are not suitable for powerful asynchronous motors. Most often they are used on compressors. Tetrodes in this case are available with insulators.
Some models have filters installed. Regulators are used both with an amplifier and without it. It is also important to note that there are modifications with resonant resistors. Their nominal input voltage parameter is on average 130 V. However, the system withstands small current overloads.
High voltage modifications
High voltage frequency converter is applicable for asynchronous motors of 10kw or more. Rectifiers in many devices are installed with a thyristor unit. 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 combat interference. Thus, the stabilization accuracytheir speed is high.
Scalar devices
Scalar converters are controlled only by modulators. In this case, you can install a remote control for changing engine power. Most often, it is single-stage scalar modifications that are offered on the market. Resistors in them are used in different types. As a rule, models are sold with one relay. Rectifiers for scalar modifications are rare. Shortwave expanders are installed with insulators.
Some modifications use trigger blocks. Such converters are well suited for high power compressors. If we talk about the parameters, it is important to note that their nominal voltage fluctuates around 220 V at a frequency of 60 Hz. The system can withstand overloads at a maximum of 5 V. The models differ in stabilization accuracy. On average, this parameter does not exceed 3%.
Vector type models
Vector converters are controlled by regulators. In this case, it is not possible to connect the remote control. Devices are produced most often of a two-stage type. For powerful asynchronous motors, these converters are suitable. It is also important to note that they use push-button and rotary types of regulators. Resistors are installed with insulators and are able to withstand a large input voltage. Most often, modifications are sold with two relays. It is also important to mention that some converters have a thyristorblock. Filters are applied only by wire type. To combat impulse noise, insulators are specified.
Devices for 5 kW asynchronous motors
Frequency converters for asynchronous motors are often installed on machines. The principle of operation of the devices is based on a phase change in frequency. Converters for asynchronous motors for 5 kW are available only in single-stage type. The modulators of the models are used, as a rule, dipole. 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 allows you to change the engine power very quickly.
Triggers are most commonly used of the two-bit type. In turn, thyristors can only be used expansion. For many converters, the rated current indicator does not exceed 230 V. Overloads, on average, devices are maintained at 20 V. The rated current parameter is 3 A. However, in this case, much depends on the conductivity of the modulator.
Modifications for 10 kW motors
Compressors and conveyors are often fitted with frequency converters for asynchronous motors. The principle of operation of the devices is based on a phase change in frequency. Models are produced, as a rule, two-stage type. Some of them have resistors of a resonant type. Contacts are used to connect the converter. Modulators are used only dipole type. The transceivers in the devices are distinguished by increased sensitivity.
Overload they are capable of maximumwithstand at 20 V. The rated voltage indicator fluctuates around 230 V. Modifications with two relays are rare. Many converters use transceivers of the chromatic type. It is also important to mention that there are devices with regulators 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 rated 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, single-stage devices are presented on the market. The principle of their operation is based on the phase change of the clock frequency. The overload parameter for models does not exceed 15 V. In turn, the operating current indicator is on average 4 A. Some modifications use selective resistors.
Thyristors on 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 come across that have a chromatic transceiver. These models are able to boast of high stability.
Modification "KVT-1"
Frequency converters "KVT-1" are used for drilling machines. In this case, the modulator is of the dipole type. It is also important to mention that this one-stagethe converter can be controlled from the remote control. He has a selective resistor with an increased current conductivity parameter. The transceiver unit for this 220 V frequency converter (3-phase output) is installed near the modulator.
Directly lowering the clock frequency is carried out by the rectifier. This model does not have an extension. If we talk about the parameters, it is important to mention that the rated voltage is 220 V, and the system can withstand overloads at a maximum of 12 V. The operating current of the converter does not exceed 3 A. The stabilization accuracy is about 2%.
DIY conveyor devices
For a conveyor, making a frequency converter with your own hands is quite simple. In this case, you should first select the relay for the device. It must withstand the rated input voltage of 220 V. The resistor for the converter will need a selective type. In total, three transceivers need to be prepared. One of them must be on the modulator to stabilize the control process. The rest of the transceivers are installed near the contacts.
Modulator for the model will need a dipole type. However, before that, it is important to install a rectifier. Most often it is selected with a conductivity of 3 microns. Expanders use both analog and switched types. A filter is required to deal with interference. The expander of the model will have to be used with insulators. The operating current in the system should be no more than 3 A. As a result, we can hope for stabilization accuracy in the region of 2%.
DIY models for mixers
For a mixer, you can 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 dipole type. It must withstand the rated input voltage 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. Beam tetrodes are used to regulate the power of engines. At the end of the work, it remains only to check the operating current in the system. On average, the accuracy of power stabilization must be 3%.
Device "KVT-2"
"KVT-2" is a powerful single-stage frequency converter. The principle of operation of the device is based on a phase change in frequency. For this, a dipole modulator is installed, which is connected to resistors of high current conductivity. The transceiver in this case is installed chromatic type. There are two thyristors in the circuit. To improve the stabilization accuracy, this single-phase frequency converter has an amplifier. The trigger in the presented device is located with insulators. The model has one relay.
Devices for reciprocating compressors
For reciprocating compressors, a two-stage frequency converter is most often selected. The principle of operation of the device is based on a phase change in frequency. Many models use two-bit type flip-flops. Thyristors in convertershave a current conductivity of 2 microns. The nominal voltage indicator is on average 230 V. The operating current in the system is maintained at around 3 A.
Tetrodes in devices are used with insulators. It is also important to note that two-stage modifications are on the market. Their nominal voltage indicator reaches 320 V. The system can withstand overloads of 30 V. The accuracy of power stabilization for models is not high. Expanders are often used of the switched type. Direct connection of models is carried out through the contacts on the rear panel of the device.
