Powerful thyristor converter 12V to 220V (500W)

Literature

Gorbachev G. N., Chaplygin E. E. Industrial electronics: Textbook for universities / Ed. V. A. Labuntsova.. - M.: Energoatom-izdat, 1988. - 320 p.

Schilling V. Schemes of rectifiers, inverters and frequency converters: Per. with him.. - L.: Gosenergo-izdat, 1950. - 464 p.

Tolstov Yu.G. Autonomous current inverters. - M.: Publishing House "Energy", 1978. - 208 p.

Chizhenko I.M. Handbook of converter technology.. - K.: Tekhnika, 1978. - 447 p.

E. I. Berkovich. Thyristor high frequency converters. - L.: Energy, 1973.

Alfred Mühlbauer. History of Induction Heating and Melting. — Vulkan-Verlag GmbH, 2008.

John William Motto, Jr. Introduction to Solid State Power Electronics. — Westinghouse Electric Corp., 1977.

Takesi FUJITSUKA. Analysis and Design of Parallel Inverter Circuit with Parallel Inductive Load. — Kyoto University, 1971.

Nikolay L. Hinov. Parallel Inverter Analysis Using Mathematical Software. — Bulgaria: 1000 Sofia, 2005.

Pantech ProLabs India Pvt Ltd. Introduction to Parallel Inverter (English) (unavailable link). Retrieved September 22, 2014. Archived January 13, 2014.

Direct frequency converters

When using a CNC, voltage from the network is supplied through controlled valves to the engine. In each phase of the NPCh, a reversible two-set converter is installed with joint or separate control of the power sets.

In Fig. Figure 1a shows a diagram of a three-phase-single-phase VFC based on three-phase zero circuits. It converts three-phase voltage into single-phase voltage, but with an adjustable frequency. Sets B and H are switched, and the output is bipolar voltage. To control converters, certain control laws are used - rectangular and sinusoidal. If a rectangular control principle is used, then the operating algorithm will be as follows: when one half-wave of voltage passes, control pulses are applied to one of the sets with a control angle (delay angle) a = const. This kit will operate in rectifier mode and then with control angle (advance angle) b = a. To reduce the current it is necessary to switch to inverter mode (Fig. 1 b). To avoid a short circuit in the inverter itself, it is necessary for the current to drop to zero - this is called a dead time. After a dead pause, the second set is switched on.

If sinusoidal control is used, then the smooth component of the output voltage should change according to a sinusoidal law; for this, the control angle a continuously changes (Fig. 1 c).

Picture 1.

Diagram of a three-phase-three-phase NPCh, made on the basis of three-phase bridge circuits. Below is the diagram.

This type of converter is not widely used due to a number of disadvantages in its use. And this is: the impossibility of completely regulating the output frequency (when using three-phase bridge circuits, the control range is 25-45 Hz, and at zero 15-45 Hz). Constant switching of valves, which leads to deterioration of the power factor, as well as poor quality of the output voltage and a large impact on the supply network.

The advantage can be recognized that such converters have a higher efficiency due to a single energy conversion.

The most common are frequency converters based on AIT and AIN on IGBT transistors, due to the best energy quality indicators at the output of the converter and their impact on the network.

Development

The electrical circuit of a thyristor converter-motor (for example, KHP) for smooth switching can be of two types:

1. Single-phase;
2. Multiphase.

Depending on the type of design, the ratios of calculation units and the operating principles of the converter vary.

Photo - zero circuit of three-phase conversion

This drawing schematically shows the change in electrical energy when the thyristor converter operates in rectifier and inverter mode. At the same time, for a bridge circuit you can make the same diagram, but only consisting of two zeros. It is this type that is most often used when designing converters for machine tools. This is due to the fact that the initial phase voltage in it is twice the phase voltage (Udo) in the zero operating circuit.

Photo - food

A single-phase circuit is used to control the power supply and drive operation of machines with high inductive reactance. It operates within a power range from 10 kW to 20, much less often at higher powers. For example, suitable for an electric oven or home machine.

Photo - single line diagram

Three-phase is used for equipment where 20 kW or more is required for operation. For example, for synchronous drives, crane and excavator engines. Another popular multiphase control circuit is six-phase (Camron). Her project involves the use of a surge reactor in the design, which is aimed at controlling low voltage and high current. This power electrical device transmits and converts electrical energy in parallel rather than serial (like most similar devices). It is more difficult to develop with your own hands, but the degree of reliability and efficiency is much greater than that of a single-phase thyristor converter. But such a reversible controller has a serious drawback - its efficiency is less than 70%.

You can make your own converter with your own hands, but a lot depends on the base used. Below is a diagram developed on the basis of Micro-Cap 9. The main feature of this model is the need for joint modeling of various nodes.

Photo - Thyristor equalizer circuit

Video: how thyristor converters work

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3-phase frequency circuit diagram

Thyristor three-phase frequency converters are used to control powerful loads and are used where it is not possible to turn on equipment using IGBT transistors.

There are two classes of devices based on the principle of switching control elements:

• With single-stage switching;
• Two-stage.

Single-stage devices have a simple circuit design, but do not have the ability to adjust the output voltage, since all thyristors are controlled simultaneously. Voltage regulation occurs by installing a constant supply voltage in the circuit through the installation of an adjustable rectifier.

In turn, two-stage converters are divided into circuits:

• With group switching;
• With phase switching;
• With individual control.

These devices are more complex not only in the control circuit, but also in the power part, since they contain two groups of thyristors: anode and cathode.

Phase commutation

Control is carried out separately for each phase of the conversion by turning off the anode or cathode thyristor.

Individual switching

Here, each thyristor of the converter is controlled separately. Due to individual control, it is possible to implement a large number of conversion algorithms, reduce signal waveform distortion and the level of electromagnetic interference to a minimum.

Circuit solutions for converters based on thyristors

Frequency converter

A feature of thyristor circuits is that they are designed to work with a certain type of load.

Series and parallel current inverters

This type of converter has an additional capacitor connected in series or parallel to the load. The purpose of the capacitor is to ensure reliable locking of thyristors that are not involved in the passage of current through the power circuit. To stabilize the current through the load, the input of the current inverter contains inductance, which ideally should tend to infinity.

Combined schemes

The combined series-parallel circuit contains two capacitors and improves the load characteristics of the device. In particular, this scheme is more stable when operating at low loads.

McMurray voltage converter

The McMurray circuit includes an LC circuit. This circuit is formed from the connection of a capacitor and an inductor through a currently open thyristor, closing the opposite one.

This solution allows you to power an inductive load, for example, devices that perform induction heating or welding of metal structures.

Series resonant inverter

In such a circuit, the capacitor capacitance and inductance are selected in such a way that the circuit is in resonance at the LC conversion frequency. Thus, the thyristors will be controlled at the resonant frequency.

Conversion can be carried out at a higher frequency, which improves the characteristics of the circuit due to better switching conditions for key elements.

Types of converting units

The conversion can be performed by various schemes, in which the operating principle is different. There are several typical uses of thyristors:

• Controlled rectifiers;
• Inverter converters.

A controlled rectifier is characterized by the fact that instead of some or all diodes, thyristors are installed, by switching which at certain points in time you can control the average voltage across the load.

Controlled rectifier

A voltage converter based on thyristors, connected according to a controlled rectifier circuit, due to the nature of its operation, can only be used in alternating current circuits to supply the load with direct voltage.

Inverter converters generate voltage, close to sinusoidal in shape, from direct voltage. In this case, a different number of phases can be obtained, and it is possible to adjust the voltage amplitude and frequency.

A frequency converter

In order to control power and speed, an asynchronous motor can only be switched on through an inverter converter (frequency drive).

IGBT transistors

By combining the positive qualities of bipolar and field-effect transistors with an insulated gate, you can obtain a very worthy switching element for low-frequency (meaning industrial frequency 50-60 Hz) technology - IGBT.
Its designation and simplified equivalent circuit are shown in the figure above. The circuit is assembled similarly to Darlington for bipolar. A field-effect transistor with an n-channel actually serves as a current amplifier with high gain, and well opens the bipolar transistor associated with it, which serves as a power transistor in this pair. Its emitter in this structure is called a collector and vice versa (according to the “duck principle” - in relation to the terminals, the device partly behaves like a bipolar transistor with a giant gain). At the same time, IGBT cannot be considered a simple circuit that is “soldered together” from n-channel field-effect and pnp bipolar transistors - this is precisely a semiconductor structure, not a circuit. The formal base-collector junction of the bipolar part and the field channel form a single structure on the crystal.

The scope of application of IGBT transistors in terms of electrical parameters lies from 300 V and above, in terms of frequency - up to 10 kHz. This is just well suited for industrial frequency (in the use of frequency generators). IGBTs are used in electric drives ranging from small power tools to electric locomotives. The fact that they operate in the region of not very high frequencies, unlike mosfet, eliminates many problems associated with parasitic inductances and capacitances - the control transistor in such a structure feels quite comfortable, its switching frequency is relatively low. This means it is easier to reload the bolt capacitance.

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In this case, high conductivity is not required from it. The output PNP bipolar transistor is designed in such a way that it can withstand high reverse voltage and can operate in inverse mode. The ease of control of IGBTs and the range of safe operation turned out to be much higher than that of bipolar transistors. IGBTs, as such, do not have a built-in flyback diode, but such a fast recovery diode can be added to the circuit either externally or integrated on-chip if needed for the application for which the device is intended.

IGBTs appeared in 1983 (the first sample was patented in IR)

The first samples did not switch well and were unreliable, so they did not enter the market properly. The difficulties were technological, related to obtaining plates with a thickness of about 100 microns

Overcoming them, as well as the emergence of Trench technology for the manufacture of MOSFETs, made it possible to sharply reduce the channel resistance in the open state, and this made it possible to bring the properties of IGBT closer to the properties of a traditional mechanical switch, but without the inherent arcing and with several orders of magnitude high performance.

IGBT transistors are used in frequency converters and soft starters; they are rapidly replacing thyristors in all areas, despite their significant price. It is used in power supplies, inverters, electric drives, welding power devices, and in transport.

Methods and circuits for controlling a thyristor or triac

Thyristors are widely used in semiconductor devices and converters. Various power supplies, frequency converters, regulators, exciters for synchronous motors and many other devices were built on thyristors, and recently they have been replaced by transistor converters. The main task for a thyristor is to turn on the load at the moment the control signal is supplied. In this article we will look at how to control thyristors and triacs.

Definition

A thyristor (thyristor) is a semiconductor semi-controlled switch. Semi-controlled means that you can only turn on the thyristor; it turns off only when the current in the circuit is interrupted or if reverse voltage is applied to it.

It, like a diode, conducts current in only one direction. That is, to be included in an alternating current circuit to control two half-waves, you need two thyristors, one for each, although not always. The thyristor consists of 4 semiconductor regions (pnpn).

Another similar device is called a triac - a bidirectional thyristor. Its main difference is that it can conduct current in both directions. In fact, it consists of two thyristors connected in parallel towards each other.

Main characteristics

Like any other electronic components, thyristors have a number of characteristics:

Voltage drop at maximum anode current (VT or Uoc).

Direct voltage in closed state (VD(RM) or Uзс).

Reverse voltage (VR(PM) or Urev).

Direct current (IT or Ipr) is the maximum current in the open state.

The maximum forward current capacity (ITSM) is the maximum peak on-state current.

Reverse current (IR) is the current at a certain reverse voltage.

Direct current in the closed state at a certain forward voltage (ID or Isc).

Constant unlocking control voltage (VGT or UУ).

Control current (IGT).

Maximum control current of the IGM electrode.

Maximum permissible power dissipation at the control electrode (PG or PU)

Principle of operation

When voltage is applied to the thyristor, it does not conduct current. There are two ways to turn it on - apply a voltage between the anode and cathode sufficient to open it, then its operation will be no different from a dinistor.

Another way is to apply a short pulse to the control electrode. The opening current of the thyristor lies in the range of 70-160 mA, although in practice this value, as well as the voltage that needs to be applied to the thyristor, depends on the specific model and instance of the semiconductor device and even on the conditions in which it operates, such as the ambient temperature environment.

In addition to the control current, there is such a parameter as the holding current - this is the minimum anode current to keep the thyristor in the open state.

After opening the thyristor, the control signal can be turned off; the thyristor will be open as long as direct current flows through it and voltage is applied. That is, in an alternating circuit the thyristor will be open during that half-wave the voltage of which biases the thyristor in the forward direction. When the voltage goes to zero, the current will also decrease. When the current in the circuit drops below the holding current of the thyristor, it will close (turn off).

Load operating principle. 3-phase frequency circuit diagram

The diagram shows the operating energy of the frequency generator. A similar diagram is made for a bridge circuit. It is more often used when designing a frequency generator for loading equipment and machine tools. The phase voltage in the circuit is increased.

A single-phase circuit is used for the power line, operating a mechanism with high inductance resistance. It operates in the power range of 10 – 20 kW, rarely at significant powers. For an electric furnace or machine in everyday life, the following scheme is used:

A three-phase circuit diagram is used for 20 kW mechanisms, synchronous motors, excavators and cranes. A popular multi-phase circuit is the 6-phase circuit. It involves the use of a low potential and high current equalizer. A current-carrying device conducts and changes electrical energy in parallel, unlike many similar devices. It is difficult to make, but its reliability is greater than that of single-phase thyristors. This controller with reverse has a negative side - its efficiency is less than 70%.

It is possible to make your own thyristor frequency converter, depending on the basis of the application. The figure shows a circuit based on Micro-Cap 9. The main advantage is the need to load several nodes together.

Features of thyristor control

Voltage converters

Unlike transistor elements, thyristors are not completely independent electronic devices that require third-party control. To open them in the conductive direction, an external influence will be required in the form of a current pulse supplied between the cathode and the control terminal of the device.

Important! If the reverse action (locking it) is necessary, it is not enough to stop the supply of control pulses. To do this, you will need to sharply reduce the value of the current flowing through it, or change the polarity of the applied anode-cathode voltage.

An exception is the so-called “locked thyristors”, which are closed by applying pulses of the required polarity to their control electrodes.

In the presence of such elements, it is much easier to manufacture a voltage converter using thyristors, since in this case the number of required components is reduced.

Additional Information. Sometimes in converter circuits (TCFs, in particular), reactive discrete components such as capacitors and chokes are installed to block triode devices in the load.

Due to the reactive nature of their operation, the electrical energy previously accumulated in them is spent on locking the already open thyristors.

In addition, in order to suppress parasitic oscillations accompanying high-speed switching of thyristors, special damping chains based on RC elements are included in parallel with them.

Determination of the amount of converted power

Where should you start the calculation? The most important parameter of any power source is power. All other parameters of the converter, including weight, dimensions and cost, directly depend on it. In this case, the output power of RO can be easily determined as the sum of the powers of both channels:

where ROUT1, ROUT2 are the output power of the first and second channels, respectively.

However, in fact, the key influence on the mass, dimensions and cost is not the output, but the converted power of the RPM - the rate of energy transfer through the magnetic or electric fields of elements that change the parameters of electrical energy. In our example, this process occurs in inductor L1, therefore all other parameters of the circuit depend on its operating mode.

In general, the amount of converted power may be less than the power of the converter. This is due to the fact that, due to the design features of the power section, part of the energy is supplied to the load directly from the primary power source (from the converter input), bypassing the magnetic field of the inductor. This issue is discussed in detail in [], where formulas are obtained that allow one to calculate the RPM value for the four most common (“basic”) schemes:

where UIN, UOUT are, respectively, the voltage at the input and output of the converter.

Our scheme, at first glance, is not one of the “basic” ones, but let’s look at it carefully. If you mentally remove from it all the elements related to the second conversion channel (winding W2, VD1, C3), then you will be left with a classic boost converter, and if you remove the elements of the first channel (VD2, C2), then you will be left with a flyback converter (Figure 3).

For the first channel (boost circuit), the converted power of RPM1 depends on the ratio of the input and output voltages, and the greater the voltage difference, the greater RPM1. Let's determine this value for the worst case - at the minimum input voltage UВХ_MIN:

In the second channel (flyback circuit), all energy passes through the magnetic field of the inductor, therefore the converted power of RPM2 does not depend on the ratio of the input and output voltages:

The magnetic circuit of the inductor L1 is common to two channels, therefore, using the principle of superposition, the total converted power of the RPM can be represented as the sum of the converted powers of the first and second channels:

Comparing the results of calculations using formulas (1) and (5), we see that RPMOUT. The missing 4 W due to electrical communication are supplied to the load of the first channel directly from the input without any conversion. This allows us to make our circuit almost 17% smaller and lighter than if both channels were connected via a flyback circuit (Figure 2b). By the way, if the reader wants to practice calculating the converted power, then Figure 2 shows the results of the RPM calculations for all inductive components, which can be used for self-test.

Powerful thyristor converter 12V to 220V (500W)

The described device is designed to convert a direct voltage of 12 V into an alternating voltage from 200 to 500 V and can deliver power up to 500 W to the load.
The converter circuit is shown in Fig. 4.40. The frequency of the output alternating voltage is determined by the pulse frequency of the self-oscillator, made on transistors VT1 and VT2. These pulses control thyristor switches VD1 and VD2 through transformer T1, which alternately connect one or the other half of the primary winding of transformer T2 to a constant voltage source. A load is connected to terminals 4-5 of transformer T2. The quality of operation of the voltage converter largely depends on the correct selection of the capacitance of capacitor C4. The capacitor is selected correctly if, with fluctuations in the supply voltage within ±10%, clear alternating closing of the keys is ensured. The use of isolation capacitors C2 and C3 increases the stability of the converter. Resistor R3 protects the power source from a short circuit when switching keys. The output voltage frequency of the device with the specified data is 200 Hz.

If you provide for the possibility of changing the frequency of the self-oscillator (for example, instead of the self-oscillator, assemble a frequency-controlled multivibrator with a power amplifier), then at the output of the converter you can obtain a voltage with a frequency of 50.400 Hz, which will allow you to use it for smooth control of the rotation speed of synchronous electric motors with a power of up to 500 W .

By changing the number of turns of the secondary winding of transformer T2 accordingly, it is possible to obtain different sizes at the output of the voltage converter. Transformer T1 is wound on a core Ш 16×10 and has windings: I - 2×40 turns PEV-2-0.8, II - 2×10 turns PEV-2-0.2 and III - 2×20 turns PEV-2-0.2. Transformer T2 is wound on a core 11150x60 and has windings: I - 2x40 turns PEV-2-3.0 and II - 800 turns PEV-2-0.92. With such data, the output voltage of the converter is 400 V. The description of the converter is given in [71].

Editor's note

Avalanche thyristors PTL-100 are quite rare devices, but in this circuit it is possible to use more common types of powerful thyristors. These thyristors must also be designed for switching currents of at least 100 A.

As a replacement, we can offer the following thyristors for a current of 100 A: T151-100 or the older T100 (both of these thyristors do not belong to the avalanche class), but only more powerful avalanche thyristors are available. These are TL171-250, TL171-320 or TL2-160, TL2-200, TL2-250. There are also high-frequency thyristors, including 100 A ones, for example, TB161-100, TC100, TCHI100. All of these powerful thyristors, despite their name, can operate at frequencies up to 500 Hz.

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Operating principle and design features

To convert the load, a thyristor high-voltage circuit converter based on IGBT is used. A thyristor-based frequency converter is a device for converting current, adjusting its parameters and current level. Using a frequency converter, you can equalize the values ​​of drive parameters on electric motors: angle, shaft speed at startup, and others.

Thyristor equalizer circuit.

For a DC motor, a thyristor converter is used. The advantages of this device have allowed it to be widely used. Benefits include:

• Efficiency (95%) for the PN-500 brand.
• Control area: motors from low power to megawatt.
• Can withstand significant impulses of engine starting loads.
• Durable and reliable operation.
• Accuracy.

This system also has disadvantages. Power is at its lowest level. This is evident in the precise regulation of the production process. Additional devices are used as compensation. Such a frequency converter cannot operate without interference. This can be seen during the operation of sensitive electrical equipment and radio devices.

Components:

1. Reactor in the form of a transformer.
2. Current rectification blocks.
3. Reactor for smoothing the transformation.
4. Overvoltage does not affect the protection.

Converters (2017) are connected through a reactor. The transformer serves to match the output and input voltage sections and equalize the voltage between them. The electrical connection circuit includes a smoothing reactor. The frequency converter has a circuit that contains a smoothing reactor.

The frequency converter passes the load. The load goes to the rectifier blocks in the output link. To equalize the power supply of several devices, induction consumers are connected on special buses.

There are two types of frequency converters - high-frequency and low-frequency. The selection of the desired model is carried out according to the necessary parameters of the electrical circuits. In 3-phase machines, the connection type is different. 1-phase current tolerates impacts, but efficiency is lost when converting to 3-phase current.

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The system is used in smelting production, control of lifting and transport devices, and welding production. This principle of load operation is implemented by an engine-generator system. At the lowest engine speeds, the spindle speed is adjusted over a wide range and different characteristics of the motor drive are adjusted.

Technical data and cost

The characteristics of thyristor frequency drivers depend on the type and options.

TFC

A thyristor-based converter operating in conditions with humidity and dust (EPU-1-1-3447E UHL4).

Thyristor converters are combined into rectification complexes. If one equalizer malfunctions, all equipment is completely repaired or dismantled. In the rectifier complex, only the mechanism that has failed is replaced. These systems are used in machine tools. The cost of equipment for the ABB DCS400 thyristor converter for 2021 is around one hundred rubles.

Frequency converters with DC link

These are devices made using a transistor or thyristor circuit. However, their main distinguishing feature is that the correct and safe operation of the frequency generator requires the presence of a constant voltage link. Therefore, to connect them to an industrial network, a rectifier is required. Typically, complete equipment is used, consisting of a frequency converter and rectifier, controlled by one control system.

The inverter of this group uses a two-stage conversion of electricity: sinusoidal U input with f = const is straightened in the rectifier (V), filtered by a filter (F), smoothed, and then re-converted by the inverter (I) into U ̴. Due to the two-stage conversion of electricity, the efficiency decreases and the weight and size indicators slightly deteriorate in comparison with frequency converters with direct coupling.

To create a sinusoidal U ̴ self-controlled frequency converters. They use an advanced thyristor and transistor base as the key base.

The main advantage of thyristor converter equipment is the ability to operate with large network parameters, while withstanding continuous load and pulsed influences. The devices have higher efficiency.

Frequency converters based on thyristors today are superior to other high-voltage drives, the power of which amounts to tens of MW with U out from 3 to 10 kV and more. However, their price is correspondingly the highest.

Advantages:

• highest efficiency;
• possibility of use in powerful drives;
• reasonable cost, despite the introduction of additional elements.

Classification of converters

Based on the type of valves used, static converters are divided into ionic (gastronic, mercury) and semiconductor (silicon, selenium, germanium, etc.); by type of valves - diode, thyristor and diode-thyristor; since the 1990s, transistor converters have become widespread. Rolling stock traction converters currently use gated thyristors (GTOs) and IGBT transistors, depending on the drive power.

According to the functions performed, rectifier converters, inverter converters and rectifier-inverter converters are distinguished; according to the method of voltage regulation - pulse (direct current), pulse-phase, zone-phase, frequency, pulse-frequency, pulse-width, etc.

Static converters can be dependent on the supply voltage (for AC EPS) and independent (for DC EPS); are carried out with natural and forced cooling, air and liquid (oil), as well as thermosyphon.

Structurally, static converters can be stationary and mobile, on EPS, in-body (in-car) and under-car.

Static converters of power circuits of substations and EPS are manufactured in the form of cabinets or panels in which valves are installed. According to the connection diagram of the valves, static converters are distinguished: 2-, 4-arm (bridge), 6-, 8-, 10-arm and others with series-parallel connection of valves.

The EPS uses static converters in traction design (see Fig.) with electric valves, made taking into account the relevant technical conditions. In low-power, low-voltage static converters, valves of general technical manufacture are used.

Semiconductor static converters are also common on the railway, they are more reliable compared to mercury ones, have smaller overall dimensions and weight, longer service life, and are non-toxic during maintenance and repair.

Static converters for EPS must provide:

EPS operability without power limitations in case of failure of one of the valves (in any arm) and in case of damage in control circuits; convenient and quick replacement of damaged valves;

stable operation when the value and shape of the supply voltage changes within the established limits.

During operation, static converters open and close in accordance with a given control algorithm, resulting in current flowing into the load at certain periods of time. One or more power static converters are installed on the EPS, each of which powers one or more traction motors. The power of such static converters is up to several thousand kW, the operating voltage is from units to several thousand V; current strength - from units to several thousand A.

Improvement of static converters is possible in the direction of improving their parameters, reducing overall dimensions and weight, reducing the number of valves while providing the same power, increasing reliability, simplifying the maintenance and repair system.

1.1. THYRISTOR VOLTAGE CONVERTER – CONTROLLED AC VOLTAGE CONVERTER

The value of the voltage supplied to the motor can be adjusted by including additional elements (resistors, saturation chokes) in the stator circuit or using thyristor voltage regulators (TRV).
The use of TRN compared to other methods of voltage regulation provides a number of advantages: for electric drives: · increases the coefficient of performance (efficiency);

· carries out stepless regulation;

· reduces weight and dimensions.

There is a wide variety of circuits (Fig. 1.1) for switching on power valves (thyristors, diodes), allowing for contactless switching of stator circuits, asynchronous motors and adjusting the level of the supplied voltage [62]. In the above diagrams, the stator windings are connected both in a star and a triangle.

Thyristor voltage regulators are made using symmetrical and asymmetrical circuits. In symmetrical circuits (Fig. 1.1 a, b, d, e), the switching element consists of two back-to-back thyristors in each phase, while control pulses are applied to the thyristor to the anode of which the positive potential of the mains voltage is applied at a given time. In asymmetrical circuits (see Fig. 1.1, c) in each phase the switching element is represented in back-to-back

parallel connected thyristor and diode. The presence of a diode in the switching element simplifies the TPV control circuit, increases reliability, but somewhat reduces the range of output voltage regulation.

In all of the above schemes, regulation of the output voltage is achieved by changing the shift angle of the thyristor unlocking pulses using a pulse-phase control system (PPCS).

The task of accurately determining the voltage supplied to the motor stator during phase control is quite complex, since its solution involves taking into account the interrelated electromagnetic processes occurring in the rotor and stator circuits. Therefore, an accurate mathematical description of electromagnetic processes is used in in-depth studies of an electric drive with a turbocharger. For approximate engineering calculations, an asynchronous motor can be represented as a three-phase active-inductive load, the parameters of which are determined from the equivalent circuit of the motor, T-shaped (Fig. 1.2, a) and L-shaped (Fig. 1.2, b).

It is convenient to consider the operation of a TVR on an active-inductive load for the case of a symmetrical circuit. If a symmetrical active-inductive load is connected to a star according to a zero circuit, then the current in each phase does not depend on the current of other phases.

In the circuit for switching on one phase (Fig. 1.3, a) at each moment of time, the value of the effective network voltage is balanced by the voltage drop across the valves and across the elements of the RL circuit:

where is the voltage drop across the valve; i – load current; – respectively, the active resistance and inductance of the motor; – phase voltage amplitude.

When the thyristors are closed, the voltage drop across the valve is equal to:

With an open thyristor, for example, VS1, assuming that the valves are ideal (direct resistance is 0), in the positive half-cycle the network voltage can be written:

The solution to equation (1.3) with respect to the load current (i) has two components: forced (ipr) and free (icv):

The forced component is determined by the phase voltage and load resistance:

where is the total resistance of the load circuit (motor); – shift angle between current and voltage.

The free current component is determined by the electromagnetic time constant of the load circuit ( ):

where ton is the moment when the thyristor is turned on.

The function indicator in expression (1.6) can be represented as:

where α = ω ton is the opening angle of the thyristor.

Substituting into expression (1.4) the value of the free current component from expression (1.6) and the forced component from expression (1.5), we obtain:

The value of coefficient A can be found from the condition that at the moment the thyristor is triggered (wt = a), the current in the load cannot change abruptly (i = 0):

The final equation for load current and voltage will be:

U = Um×sin(w×t) for a £ w×t £ a + l;

I = 0 or U = 0 for a + l – p – l / tan = 0. (1.11)

The dependence of l on a and j can be found using a computer.

Similar expressions can be obtained by analyzing the processes in the load when opening the thyristor VS2 (avs2 = p + avs1).

Graphs of changes in currents and voltages when switching an RL load are shown in Fig. 1.3, b. The graphs are plotted for the case when the firing angle of the thyristor VS1 exceeds the shift angle (j) between current and voltage. Angle a = j is the minimum opening angle of the thyristors. Indeed, if a p. In this case, for some periods of time, both thyristors must conduct current simultaneously, which is impossible, since the voltage drop across the conducting valve creates reverse polarity of the voltage at the closed valve.

The maximum firing angle of the thyristors for the circuit under consideration (see Fig. 1.1, a) a = p. When the control angle changes within j £ a £ p, a non-sinusoidal voltage is applied to the load, and an intermittent current flows. The harmonic composition of currents and voltages at the load depends on the connection circuit of the TVR.

The characteristics of TRN are considered in the form of a family of characteristics UTRN=f(a,j) [63]. Usually the output voltage of the TRN is represented only by its first

harmonic, since other harmonics (higher odd) have a slight effect on the motor torque.

For a controlled electric drive, it is advisable to construct a family of control characteristics:

at fixed values ​​of the load angle j = const [62]. In Fig. 1.4. The adjustment characteristics of the TRI are given for two variants of converter construction circuits: symmetrical (see Fig. 1.1, b) and asymmetrical (see Fig. 1.1, c).

The pulse-phase control system is not fundamentally different from the SIFU of a thyristor DC converter. Usually it is built according to the vertical principle, while requirements for the width of the unlocking pulses are imposed on it. Taking into account that the load angle values ​​for asynchronous motors

are in the range from jmin

90°, the width of the unlocking pulses should be greater:

Single-channel asynchronous SIFU, used in industrial thyristor voltage regulators such as thyristor control stations (TCS) SIFU - analog-to-digital with a vertical control principle (Fig. 1.5), consists of five main units: an analog-to-digital converter, a generator, a counter, a decoder and six "OR" circuits. For each sync pulse “Sync.” in accordance with the control signal, the analog-to-digital converter generates a pulse that sets the counter to the zero state, at the same time the generator starts, and the counter begins to count the pulses generated by the generator. In accordance with the contents of the counter, a signal is issued from the corresponding output of the decoder (duration 60º).

Types of converters

Among the variety of existing types of converters, the following classes are distinguished:

• special devices for home;
• high-voltage and high-frequency equipment;
• transformerless and inverter pulse devices;
• DC voltage converters;
• adjustable devices.

This category of electronic devices includes current-to-voltage converters.

Equipment for home

The average user encounters this type of converter devices all the time, since most models of modern technology have a built-in power supply. The same class includes uninterruptible power supplies (UPS) that have a built-in battery.

In some cases, household converters are made using a double ring (inverter) circuit.

Due to this conversion from a direct current source (a battery, for example), it is possible to obtain an alternating voltage of a standard value of 220 Volts at the output. A feature of electronic circuits is the ability to obtain a purely sinusoidal signal of constant amplitude at the output.

Adjustable devices

These units are capable of increasing the output voltage and increasing it. In practice, more often there are devices that allow you to smoothly change the reduced value of the output potential.

The classic case is when the input is 220 Volts, and the output produces an adjustable constant voltage ranging from 2 to 30 Volts.

Transformerless devices

Transformerless (inverter) units are built according to the electronic principle, which involves the use of a separate control module. As an intermediate link, they use a frequency converter, which converts the output signal to a form convenient for rectification. In modern models of inverter equipment, programmable microcontrollers are often installed, which significantly improve the quality of conversion control.

High-voltage devices are represented by the already described station transformers, which increase and decrease the transmitted voltage in the required ratios.

When transmitting energy through high-voltage lines and subsequent transformation, they strive to reduce its losses in watts to a minimum.

This class also includes devices that generate a signal to control the beam in a television tube (kinescope).

Insulated Gate Bipolar Transistor

The title of this section translates to “insulated gate bipolar transistor.” This is a modern device that appeared around the end of the last century and made a revolution in power electronics. Electricity has been used by mankind for a long time; with the development of technology, one part of the emerging problems was successfully solved, such as the abandonment of expensive magnetic alloys in favor of cheap steel and copper field windings in DC motors and magnets (Werner Siemens). The other part of the problems remained stubbornly resistant to solution for a long time. This includes, for example, the use of alternating current in electric vehicles.

Electrical devices always contain switching elements and these are their most painful areas. When many electrical circuits break, an arc occurs that burns out the contacts over time. The contact resistance should ideally be no more than the smallest section of the rest of the circuit, but in practice, it is thanks to the oxides from the arc that increased resistance occurs at the contact point. According to the Joule-Lenz law, thermal power appears and dissipates at this resistance, proportional to the resistance and the square of the current. Heating of the contact point by current leads to its accelerated aging, the further, the faster, and as a result the circuit fails.

Advantages of thyristor converters

TFCs have been very widely used due to their many advantages. The main advantage of thyristor converters in comparison with electric machine converters is that due to high efficiency, as well as the absence of no-load losses, there is a tendency to reduce power consumption from the network, and at the same time operating costs are reduced. Also, a great advantage of thyristor frequency converters is their regulation properties. Regulation of output parameters and power can be carried out without switching in power circuits. This eliminates the need for large switching devices.

We recommend that you study How to set up a motion sensor

Before you decide to buy a frequency converter, you need to familiarize yourself with its advantages, namely:

• high-quality element base from European manufacturers;
• high reliability and durability;
• simplicity and ease of use;
• high efficiency 93-95%;
• high resistance to short circuits in the load;
• ability to withstand powerful pulse overvoltages at the input;
• internal self-diagnosis and protection of all power elements;
• remote control and regulation from the remote control panel;
• digital display of converter parameters;
• cooling of the TFC is water double-circuit with a heat exchanger;
• the ability to adapt to existing equipment;
• easily reconfigurable parameters;
• individual modification at the request of the Customer;
• prompt delivery of components and spare parts;
• warranty and service;
• training of customer personnel;
• replacement of obsolete machine generators with TFCs.

Thyristor frequency converters ТПЧ-350-1 Thyristor frequency converters ТПЧ-350-1 Thyristor frequency converters ТПЧ-1600-0.5 Thyristor frequency converters Thyristor frequency converters ТПЧ-350 Thyristor frequency converters and induction furnace

Specifications

Technical description and price overview

The characteristics of thyristor converters depend on the type of their design and functional features.

TFC:

TPE-400/400-460:

EPU-1-1-3447E UHL4 (the manufacturer states that this converter can operate in difficult conditions, increased dust and humidity):

But thyristor converters are sold not only one unit at a time, but also in the form of rectifying complexes (KTEU). If a single equalizer needs complete repair or dismantling due to breakdown, then the complex replaces the failed equipment. Such systems are used both in machine tool drives and in EKT (complete thyristor electric drives).

Let's look at the price of the ABB DCS400 thyristor converter:

You can buy the device at any electrical goods store; the price list depends on the characteristics and type of execution.

Why is it worth buying a frequency converter from Termolit LLC

Today, Termolit is a leader in both the domestic and foreign markets of induction equipment. Deliveries are made to Russia, Belarus, Poland, Estonia, Germany, Israel and many other countries.

The Termolit enterprise produces a wide range of modern induction equipment, in particular thyristor frequency converters of the TFC series of various powers.

Scope of delivery: TFC cabinet and operational documents. Also, for an additional cost, the following can be supplied: replaceable backup control units, a repair kit, spare parts, and a remote control. The purpose of replaceable backup units is to reduce the time to restore functionality in the event of a malfunction in the TFC control system, as well as to reduce the changeover time when operating one TFC for different loads in turn.

The Termolit enterprise today is:

• affordable prices from the manufacturer;
• order execution in the shortest possible time;
• the quality of manufactured equipment is at the highest level;
• the possibility of individual development of equipment at the customer’s request;
• reliability and durability of products.

In order to buy a frequency converter at an affordable price, contact Termolit. You will purchase quality equipment directly from the manufacturer, without overpaying to intermediaries. The company provides warranty and post-warranty service on mutually beneficial terms with the customer.

HIGH FREQUENCY TRANSISTOR GENERATOR INVERTER FOR INDUCTION HEATING

Digital microprocessor control system TFC 320

Microprocessor control systems TFC 320 regulate, protect and diagnose. It is formed on a board with microcircuits and a screen through cables. This system guarantees reliable operation and protects against interference.

An impulse is transmitted to each valve. The information is displayed on the panel screen. Information can be obtained from the circuit mechanisms. The control system processes a lot of data transmitted via communication. This is the data:

• Power.
• Frequency.
• Loading weight.
• Weight of molten metal.
• Time.

Complete set of cabinet TFC 320:

• Rectifier.
• Power leveling system.
• Smoothing throttle.
• Diagnostics.
• Temperature control.
• Cooling control.
• Door lock.
• Protection, restart of the frequency generator when the power line is disconnected.

Operating conditions TFC 320

Reversible thyristor converters Operating principle and design

IGBT modules

Since IGBTs, as a rule, are extremely rarely used in a single version, designers began to think about modular options for their layout. The module is much simpler and more compact to use in products. But not only that.

However, the intervention of sufficiently qualified engineers will be required, since we are talking about reworking the frequency circuit, since not all models allow such an expansion: there are no outputs for such connections, and not a word in the instructions, except, perhaps, a ban on interfering with converter diagram on the consumer side and disclaimer for such cases. In addition to the technical side of the matter, there is also a possible legal one: possible violation of patents, licenses, etc. This should also be kept in mind.

Circuit solutions for converters based on thyristors

A feature of thyristor circuits is that they are designed to work with a certain type of load.

Series and parallel current inverters

This type of converter has an additional capacitor connected in series or parallel to the load. The purpose of the capacitor is to ensure reliable locking of thyristors that are not involved in the passage of current through the power circuit. To stabilize the current through the load, the input of the current inverter contains inductance, which ideally should tend to infinity.

Combined schemes

The combined series-parallel circuit contains two capacitors and improves the load characteristics of the device. In particular, this scheme is more stable when operating at low loads.

Serial, parallel and combined circuits

McMurray voltage converter

The McMurray circuit includes an LC circuit. This circuit is formed from the connection of a capacitor and an inductor through a currently open thyristor, closing the opposite one.

McMurray scheme

This solution allows you to power an inductive load, for example, devices that perform induction heating or welding of metal structures.

Series resonant inverter

In such a circuit, the capacitor capacitance and inductance are selected in such a way that the circuit is in resonance at the LC conversion frequency. Thus, the thyristors will be controlled at the resonant frequency.

Conversion can be carried out at a higher frequency, which improves the characteristics of the circuit due to better switching conditions for key elements.

How to make a frequency converter yourself

Many hobbyists try to make frequency converters with their own hands.

Homemade inverter circuit

The circuit works well with a motor with a power of up to 1 kW, made in Russia and abroad.

To make an inverter you will need the following parts:

• microcircuits: K155LA3, K155IE4, K155LP5;
• transistors: KT315 (3 pcs.), KT817V (3 pcs.);
• diodes: KD105G – 3 pcs.;
• resistors with resistance: 10 kOhm (3 pcs.), 6.2 kOhm (3 pcs.), 1 kOhm (3 pcs.), 220 Ohm and a variable resistor of 1 kOhm;
• capacitors: 0.33 and 0.1 µF;
• electrolytic capacitors: 100 µF*10 V and 1000 µF*50 V.

This self-made frequency generator definitely needs a 27 V and 5 V DC power supply. The electric motor is connected according to the diagram.

Including an electric motor in a circuit

If we turn to modern technologies, then the creation of an inverter can be done on the basis of the Arduino platform. Frequency regulators are an indispensable thing for controlling electric drives, both in domestic and industrial environments.

Three-phase inverters

Thyristor (GTO) traction converter according to the Larionov-star scheme

Three-phase inverters are typically used to produce three-phase current for electric motors, such as to power a three-phase induction motor. In this case, the motor windings are directly connected to the inverter output.

High-power three-phase inverters are used in traction converters in the electric drive of locomotives, motor ships, trolleybuses (for example, AKSM-321), trams, rolling mills, drilling rigs, and in inductors (induction heating installations).

The figure shows a diagram of a thyristor traction converter according to the Larionov-star circuit. Theoretically, another version of Larionov’s “Larionov-triangle” circuit is possible, but it has different characteristics (equivalent internal active resistance, copper losses, etc.).

Power semiconductor thyristors

Designed for use in rectifiers, inverters, pulse regulators, DC and AC converters, generator excitation systems and other DC and AC circuits. Depending on the type of device, thyristors can be used in pulse-width systems for starting and speed control of urban electric rolling stock, welding equipment, for completing converter devices for DC power lines, for operation in contactless switching and control equipment and other devices.

Low frequency thyristors

Thyristors T-253-800, T-253-1000 allow exposure to sinusoidal vibration in the frequency range 1-100 Hz with an acceleration of 49 m/s2 and multiple shocks lasting 2-15 ms with an acceleration of 147 m/s2.

High-speed thyristors

Thyristors TB-133-250, TB-143-400 are used primarily in those power plants that require short on and off times, as well as high critical rates of voltage rise in the closed state and current in the open state. These thyristors have increased load capacity at high frequencies.

Industrial applications of the main types of power thyristors:

• thyristors T-161, T-171 are used in electrical and radio-electronic devices for general purposes for direct and alternating current;
• Thyristors T-123, T-133, T-143, T-153, T-173 are intended for use in controlled and semi-controlled rectifiers at traction substations, in AC regulators, in soft starters, in powerful electric drives for synchronous electric motors, in converters for electric arc furnaces, in high-power reactive power compensators;
• thyristors TB-233, TB-333, TB-243, TB-453, TB-173 are used in electric welding heating and melting inductors, in electric transport, in AC electric drives, in uninterruptible power supplies, in power plants that require short turn-off time and turning on thyristors;
• Thyristors TBI-233, TBI-343, TBI-353, TBI-173 are intended for use in converters of thyristor variable-frequency electric drives, as well as in converters for other purposes that use electricity conversion at a higher frequency (up to 10 kHz).

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