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 adjust their power. 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, scalar and vector modifications exist. In order to understand the devices in more detail, you should consider the standard converter circuit.
Converter circuit
A typical 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 the selective type. It is also important to note that transceivers are installed on models. There are contacts for connecting the device. Regulators are most often installed on the control unit. Some modifications use an expander. It should also be noted that for the safe operation of the device, different types of insulators are installed.
Single-stage modifications
Tetrodes are installed on each single-stage frequency converter. The principle of operation of models is based on a change in 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 conversion process takes place directly 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, usually for compressors. In some cases, they are mounted on pumps. The rated voltage of the device is maintained at 220 V. The operating current is on average 3A. The speed stabilization models differ in accuracy of stabilization. Frequency converter error most often occurs due to network congestion.
Two-stage models
Triggers are installed only on a two-stage frequency converter. The principle of operation of the models is based on a change in the phase frequency in the circuit. Unlike the previous type, current conversion begins in the thyristor unit. Before this, the straightening process is carried out. At this stage, the limit frequency drops to a level of 45 Hz.
The rated voltage of the device can withstand 320 V. In turn, the indicator of the operating current does not exceed 5A. In some versions of the resistors are used selective type. Modulators in this case are installed with regulators. The transducers are directly connected via the contacts located on the rear panel. Two-stage devices for various machine tools and drives are used.
Low voltage modifications
Low-voltage models are made on the basis of diode rectifiers. As a rule, the 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. Regulators are used both with and without an amplifier. It is also important to note that there are modifications with resonant resistors. The parameter of the rated input voltage on average is 130 V. However, the current overloads of the system are small.
High voltage modifications
A high-voltage frequency converter is used for induction motors of 10 kW or more. Rectifiers in many devices are installed with a thyristor unit. Resistors are most often used selective type. Today you can meet a high-voltage frequency converter with two relays. Overload currents such systems can withstand large. It is also important to note that the devices are equipped with filters to combat interference. Thus, their speed stabilization accuracy is high.
Scalar devices
Scalar transducers are controlled only by modulators. In this case, you can install a remote control to remotely change engine power. Most often, it is the single-stage scalar modifications that are offered on the market. Resistors are used in different types. Typically, models are sold with one relay. Rectifiers in scalar modifications are rare. Shortwave extenders 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 the indicator of their rated voltage fluctuates around 220 V at a frequency of 60 Hz. The system is able to 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 knobs. In this case, there is no way to connect the remote. Devices are most often produced in a two-stage type. For powerful induction motors, these converters are suitable. It is also important to note that the regulators they use are push-button and rotary type. Resistors are installed with insulators and can withstand a large input voltage. Most often, modifications are sold with two relays. It is also important to mention that some converters have a thyristor unit. Filters are used only wired type. To combat impulse noise insulators are trapped.
Devices for 5 kW induction motors
Frequency converters for induction motors are often installed on machines. The principle of operation of devices is based on a phase change in frequency. Converters for 5 kW asynchronous motors are available in a single-stage type only. Modulators in models are used, as a rule, dipole. In some versions, thyristor units are installed. It is also important to note that there are many models with expanders on the market. All this allows you to quickly change the engine power.
Triggers are most often used in a two-digit type. In turn, thyristors can only be used expansion. For many converters, the rating of the rated current does not exceed 230 V. Overloads on average devices withstand at 20 V. The parameter of the rated current is 3 A. However, in this case, much depends on the conductivity of the modulator.
Modifications for 10 kW engines
Frequency converters for induction motors are often installed on compressors and conveyors. 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. Some of them have resonant type resistors. Contacts are used to connect the converter. Modulators are used only dipole type. Transceivers in devices are distinguished by increased sensitivity.
Overloads they can withstand a maximum of 20 V. The rated voltage indicator fluctuates around 230 V. Modifications with two relays are rare. Many transducers use chromatic transceivers. It is also important to mention that devices with regulators are on the market. Amplifiers are used to improve system stabilization. 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.
Submersible Pump Devices
The frequency converter for a submersible pump is manufactured with a dipole modulator. Most often, single-stage devices are presented on the market. Their principle of operation is based on a phase change in the clock frequency. The overload parameter of the models does not exceed 15 V. In turn, the operating current indicator is on average 4 A. For some modifications, selective resistors are used.
Thyristors on the frequency converter for the pump are installed with insulators. To combat impulse noise extenders are used. 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 of high stability.
Modification "KVT-1"
KVT-1 frequency converters are used for drilling machines. In this case, the modulator has a dipole type. It is also important to mention that the indicated single-stage converter can be controlled from a 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 due to the rectifier. The extender for this model is missing. If we talk about the parameters, it is important to mention that the rated voltage is 220 V, and the system withstands 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 the 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 a rated input voltage of 220 V. A resistor for the converter will need a selective type. Total transceivers need to prepare three. One of them must be 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 this, it is important to install a rectifier. Most often, it is selected with a conductivity of 3 microns. Extenders use both analog and switched type. To combat interference, a filter is required. The extender in 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 an accuracy of stabilization in the region of 2%.
DIY Mixer Models
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 by the dipole type. It must withstand a nominal 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. To regulate the power of the engines, beam tetrodes are used. At the end of the work, it remains only to check the operating current in the system. On average, the accuracy of power stabilization should be 3%.
KVT-2 device
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 high current conductors. The transceiver in this case is set to chromatic type. There are two thyristors in the circuit. To increase 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-digit type triggers. Thyristors in converters have a current conductivity of 2 microns. The rated voltage indicator averages 230 V. The operating current in the system is maintained at 3 A.
Tetrodes in devices are used with insulators. It is also important to note that there are two-stage modifications on the market. The rating of their rated voltage reaches 320 V. The system can withstand overloads of 30 V. The accuracy of power stabilization in models is not high. Extenders are often used switch type. Directly connecting the models is through the contacts on the rear panel of the device.