Regulator on a triac inductive load circuit. The principle of operation of triac power regulators

In electrical engineering, it is quite often necessary to meet with the tasks of regulating alternating voltage, current or power. For example, to regulate the rotational speed of the shaft of a collector motor, it is necessary to regulate the voltage at its terminals; to control the temperature inside the drying chamber, it is necessary to regulate the power released in the heating elements, to achieve a smooth shockless start of an induction motor - to limit its starting current. A common solution is a device called a thyristor regulator.

The device and principle of operation of a single-phase thyristor voltage regulator

Thyristor regulators are single-phase and three-phase, respectively, for single-phase and three-phase networks and loads. In this article we will look at the simplest single-phase thyristor regulator - in other articles. So, Figure 1 below shows a single-phase thyristor voltage regulator:

Fig. 1 Simple single-phase thyristor regulator with resistive load

The thyristor regulator itself is circled in blue lines and includes thyristors VS1-VS2 and a pulse-phase control system (hereinafter referred to as SPPC). Thyristors VS1-VS2 are semiconductor devices that have the property of being closed for current flow in a normal state and being open for current of one polarity when a control voltage is applied to its control electrode. Therefore, to operate in AC networks, two thyristors are required, connected in different directions - one for the flow of a positive half-wave of the current, the second for a negative half-wave. This connection of thyristors is called counter-parallel.

Single-phase thyristor regulator with resistive load

The thyristor regulator works like this. At the initial moment of time, voltage L-N is applied (phase and zero in our example), while control voltage pulses are not supplied to the thyristors, the thyristors are closed, there is no current in the load Rн. After receiving a command to start, the SPPU begins to generate control pulses according to a specific algorithm (see Fig. 2).

Fig. 2 Diagram of voltage and current in resistive load

First, the control system synchronizes with the network, that is, it determines the point in time at which the L-N network voltage is zero. This point is called the moment of crossing zero (in foreign literature - Zero Cross). Then a certain time T1 is counted from the moment of the zero crossing and a control pulse is applied to the thyristor VS1. In this case, the thyristor VS1 opens and current flows through the load along the path L-VS1-Rn-N. Upon reaching the next transition through zero, the thyristor automatically closes, since it cannot conduct current in the opposite direction. Next, the negative half-cycle of the mains voltage begins. The SPFU again counts the time T1 relative to the already new moment when the voltage crosses zero and generates a second control pulse for the thyristor VS2, which opens, and the current flows through the load along the path N-Rn-VS2-L. This method of voltage regulation is called phase-pulse.

T1 time is called thyristor firing delay time, T2 time is thyristor conduction time. By changing the unlocking delay time T1, it is possible to adjust the value of the output voltage from zero (no pulses are supplied, thyristors are closed) to full mains voltage, if pulses are supplied immediately at the moment of zero crossing. The unlocking delay time T1 varies between 0..10 ms (10 ms is the duration of one half-cycle of the standard 50 Hz mains voltage). They also sometimes talk about the times T1 and T2, but they do not operate with time, but with electrical degrees. One half-cycle is 180 e.

What is the output voltage of a thyristor regulator? As you can see from Figure 2, it resembles the "clipping" of a sinusoid. Moreover, the longer the time T1, the less this "cut" resembles a sinusoid. An important practical conclusion follows from this - with phase-pulse regulation, the output voltage is non-sinusoidal. This leads to a limitation of the field of application - the thyristor regulator cannot be used for loads that do not allow power supply with non-sinusoidal voltage and current. Also in Figure 2, the diagram of the current in the load is shown in red. Since the load is purely active, the current waveform follows the voltage waveform in accordance with Ohm's law I \u003d U / R.

The active load case is the most common. One of the most common applications of a thyristor regulator is voltage regulation in heating elements. By adjusting the voltage, the current and the power released in the load change. Therefore, sometimes such a regulator is also called thyristor power regulator... This is true, but nevertheless a more correct name is a thyristor voltage regulator, since it is the voltage that is regulated in the first place, and the current and power are already derivatives.

Regulation of voltage and current in active-inductive load

We have considered the simplest case of active load. Let us ask ourselves the question, what will change if the load has an inductive component in addition to the active one? For example, an active resistance is connected through a step-down transformer (Fig. 3). By the way, this is a very common case.

Fig. 3 Thyristor regulator operates on RL-load

Let's take a closer look at Figure 2 from the case of a purely active load. It can be seen that immediately after the thyristor is turned on, the current in the load almost instantly increases from zero to its limit value, due to the current value of the voltage and load resistance. It is known from the electrical engineering course that inductance prevents such an abrupt increase in current, so the voltage and current diagram will have a slightly different character:

Fig. 4 Voltage and current diagram for RL-load

After switching on the thyristor, the current in the load increases gradually, due to which the current curve is smoothed. The larger the inductance, the smoother the current curve. What does it give in practice?

- The presence of sufficient inductance makes it possible to bring the current shape closer to a sinusoidal one, that is, the inductance acts as a sine filter. In this case, this presence of inductance is due to the properties of the transformer, but often inductance is deliberately introduced in the form of a choke.

- The presence of inductance reduces the amount of noise propagated by the thyristor regulator through the wires and into the radio air. A sharp, almost instantaneous (within a few microseconds) rise in current causes interference that can interfere with the normal operation of other equipment. And if the supply network is "weak", then there is quite a curiosity - the thyristor regulator can "jam" itself with its own interference.

- Thyristors have an important parameter - the value of the critical rate of rise of the current di / dt. For example, for the SKKT162 thyristor module, this value is 200 A / μs. Exceeding this value is dangerous, as it can lead to thyristor failure. So the presence of inductance makes it possible for the thyristor to remain in the area of \u200b\u200bsafe operation, guaranteed not to exceed the maximum di / dt value. If this condition is not met, then an interesting phenomenon can be observed - thyristor failure, while the thyristor current does not exceed their nominal value. For example, the same SKKT162 can fail at a current of 100 A, although it can work normally up to 200 A. The reason will be the excess of the rate of rise of the current di / dt.

By the way, it should be noted that there is always inductance in the network, even if the load is purely active. Its presence is caused, firstly, by the inductance of the windings of the supply transformer substation, secondly, by the intrinsic inductance of wires and cables and, thirdly, by the inductance of the loop formed by the supply and load wires and cables. And most often this inductance is enough to ensure that the di / dt does not exceed the critical value, so manufacturers usually do not put thyristor regulators in, offering them as an option to those who are concerned about the "cleanliness" of the network and the electromagnetic compatibility of devices connected to it.

Let's also pay attention to the voltage diagram in Figure 4. It also shows that after crossing zero, a small voltage surge of reverse polarity appears on the load. The reason for its occurrence is the delay in the current drop in the load by inductance, due to which the thyristor continues to be open even with a negative half-wave of the voltage. The thyristor is turned off when the current drops to zero with some delay relative to the moment of zero crossing.

Inductive load case

What happens if the inductive component is much larger than the active component? Then we can talk about the case of a purely inductive load. For example, such a case can be obtained by disconnecting the load from the output of the transformer from the previous example:

Figure 5 Thyristor regulator with inductive load

An idle transformer is an almost ideal inductive load. In this case, due to the high inductance, the turn-off moment of the thyristors shifts closer to the middle of the half-cycle, and the shape of the current curve is smoothed as much as possible to an almost sinusoidal shape:

Figure 6 Current and voltage diagrams for inductive load case

At the same time, the voltage across the load is almost equal to the full mains voltage, although the unlocking delay time is only half a half-cycle (90 electrical degrees) That is, with a high inductance, we can talk about a shift in the control characteristic. With an active load, the maximum output voltage will be at an unlocking delay angle of 0 electrical degrees, that is, at the moment of crossing through zero. With an inductive load, the maximum voltage can be obtained at an unlocking delay angle of 90 electrical degrees, that is, when the thyristor is unlocked at the moment of maximum mains voltage. Accordingly, in the case of active-inductive load, the maximum output voltage corresponds to the angle of the unlocking delay in the intermediate range of 0..90 electrical degrees.

The article describes how a thyristor power regulator works, the circuit of which will be presented below

In everyday life, very often there is a need to regulate the power of household appliances, for example, an electric stove, a soldering iron, boilers and heating elements, in transport - engine speed, etc. The simplest amateur radio design comes to the rescue - a power regulator on a thyristor. It is not difficult to assemble such a device, it can become the very first home-made device that will perform the function of adjusting the temperature of the soldering iron tip of a novice radio amateur. It should be noted that ready-made soldering stations with temperature control and other pleasant functions are much more expensive than a simple soldering iron. A minimal set of parts allows you to assemble a simple wall-mounted thyristor power regulator.

For your information, surface mounting is a way of assembling electronic components without the use of a printed circuit board, and with good skill, it allows you to quickly assemble electronic devices of medium complexity.

You can also order a thyristor regulator, and for those who want to figure it out on their own, a diagram will be presented below and the principle of operation will be explained.

Incidentally, this is a single-phase thyristor power regulator. Such a device can be used to control power or speed. However, first you need to understand, because this will allow us to understand for what load it is better to use such a regulator.

How does a thyristor work?

A thyristor is a controlled semiconductor device capable of conducting current in one direction. The word "controlled" is used for a reason, because with its help, unlike a diode, which also conducts current to only one pole, you can choose the moment when the thyristor starts to conduct current. The thyristor has three outputs:

• Anode.
• Cathode.
• Control electrode.

In order for the current to start flowing through the thyristor, the following conditions must be met: the part must be in a live circuit, a short pulse must be applied to the control electrode. Unlike a transistor, thyristor control does not require holding the control signal. This is not the end of the nuances: the thyristor can be closed only by interrupting the current in the circuit, or by forming a reverse anode-cathode voltage. This means that the use of a thyristor in DC circuits is very specific and often unreasonable, but in AC circuits, for example, in such a device as a thyristor power regulator, the circuit is built in such a way that a condition for closing is provided. Each of the half-waves will close the corresponding thyristor.

You, most likely, do not understand everything? Do not despair - the process of the finished device will be described in detail below.

Scope of thyristor regulators

In what circuits is it effective to use a thyristor power regulator? The circuit allows you to perfectly regulate the power of heating devices, that is, to affect the active load. When working with a highly inductive load, the thyristors may simply not close, which can lead to the failure of the regulator.

Can you motor?

I think many of the readers have seen or used drills, angle grinders, which are popularly called "grinders", and other power tools. You may have noticed that the number of revolutions depends on the depth of pressing the trigger of the device. It is in this element that such a thyristor power regulator is built (the diagram of which is shown below), with the help of which the number of revolutions is changed.

Note! The thyristor regulator cannot change the speed of induction motors. Thus, the voltage is regulated on brushed motors equipped with a brush assembly.

One and two thyristor circuit

A typical circuit for assembling a thyristor power regulator with your own hands is shown in the figure below.

The output voltage of this circuit is from 15 to 215 volts, in the case of using these thyristors installed on the heat sinks, the power is about 1 kW. By the way, the switch with the dimmer is made according to a similar scheme.

If you do not need full voltage regulation and just get 110 to 220 volts at the output, use this diagram, which shows a half-wave power regulator on a thyristor.

How it works?

The information described below is valid for most schemes. The letter designations will be taken in accordance with the first circuit of the thyristor regulator

The thyristor power regulator, the principle of which is based on phase control of the voltage value, also changes the power. This principle is that, under normal conditions, the load is acted upon by an alternating voltage of the household network, which changes according to a sinusoidal law. Above, when describing the principle of operation of a thyristor, it was said that each thyristor works in one direction, that is, it controls its half-wave from a sinusoid. What does it mean?

If, with the help of a thyristor, the load is periodically connected at a strictly defined moment, the value of the effective voltage will be lower, since a part of the voltage (the effective value that "gets" to the load) will be less than the mains voltage. This phenomenon is illustrated in the graph.

The shaded area is the area of \u200b\u200bstress that is under load. The letter "a" on the horizontal axis indicates the moment when the thyristor opens. When the positive half-wave ends and a period with a negative half-wave begins, one of the thyristors closes, and at the same moment the second thyristor opens.

Let's figure out how our thyristor power regulator works specifically

The first scheme

Let's stipulate in advance that instead of the words "positive" and "negative" will be used "first" and "second" (half-wave).

So, when the first half-wave begins to act on our circuit, capacities C1 and C2 begin to charge. Their charge rate is limited by potentiometer R5. this element is variable, and with its help the output voltage is set. When the voltage required to open the dynistor VS3 appears on the capacitor C1, the dynistor opens, a current flows through it, with the help of which the thyristor VS1 will be opened. The moment of breakdown of the dinistor is the point "a" on the chart presented in the previous section of the article. When the voltage value passes through zero and the circuit is under the second half-wave, the thyristor VS1 closes, and the process is repeated again, only for the second dynistor, thyristor and capacitor. Resistors R3 and R3 are used for control, and R1 and R2 are used for thermal stabilization of the circuit.

The principle of operation of the second circuit is similar, but it controls only one of the half-waves of the alternating voltage. Now, knowing the principle of operation and the circuit, you can assemble or repair a thyristor power regulator with your own hands.

The use of the regulator in everyday life and safety

It must be said that this circuit does not provide galvanic isolation from the network, therefore there is a danger of electric shock. This means that you should not touch the regulator elements with your hands. An insulated housing must be used. You should design the design of your device so that, if possible, you can hide it in an adjustable device, find free space in the case. If the adjustable device is stationary, then it generally makes sense to connect it through a switch with a dimmer. Such a solution will partially protect against electric shock, eliminate the need to search for a suitable case, has an attractive appearance and is manufactured by an industrial method.

The thyristor charging unit by Krasimir Rilchev is designed to charge the batteries of trucks and tractors. It provides a continuously adjustable (RP1 resistor) charging current up to 30 A. The principle of regulation is a phase-pulse based thyristor, which provides maximum efficiency, minimum power dissipation and does not require powerful rectifier diodes. The mains transformer is made on a magnetic core with a cross section of 40 cm2, the primary winding contains 280 turns of PEL-1.6, the secondary 2x28 turns of PEL-3.0. Thyristors are installed on 120x120 mm heatsinks. ...

For the "SIMPLE SOLDERING TIP TEMPERATURE REGULATOR"

Consumer electronics SIMPLE TEMPERATURE SOLDERING UNITS GRISCHENKO 394000, Voronezh, Malo-Smolnskaya st., 6 - 3. This circuit is not my own design. The first time I saw her was in the magazine "Radio". I think it will interest many radio amateurs with its simplicity. The device allows you to adjust the power of the soldering iron from half to maximum. With the elements indicated on the diagram, the power load should not exceed 50 W, but within an hour the circuit can transfer a load of 100 W without any special consequences. The regulator circuit is shown in the figure. If the VD2 thyristor is replaced by KU201, and the VD1 diode - by KD203V, the connected power can be increased significantly. Output power is minimal in the leftmost (according to the diagram) position of the R2 engine. In my version, it is mounted in a desk lamp stand by the surface mounting method. This saves one power outlet, which, as you know, is always in short supply. This one has been working for me for 14 years without any complaints. Literature 1. Radio, 1975, N6, C.53 ....

For the "POWER REGULATOR WITH FEEDBACK" diagram

For the diagram "VOLTAGE CONVERTER PN-32"

VOLTAGE CONVERTER PN-32 (C) RINTELSai Oleg, (RA3XBJ). The converter is designed to power equipment with a nominal voltage of 12 V (CB radio stations, radio tape recorders, televisions, etc.) from the on-board network of cars with a voltage of 24 V. Maximum current load converter up to 3A for a short time and 2-2.5 A for a long time (determined by the radiator area of \u200b\u200bthe output transistor). Efficiency 75-90% depending on the load current. The converter circuit does not contain scarce parts. The choke is wound on a ferrite ring with a diameter of 32 mm and has 50 turns of PETV-0.63 wire. Dimensions of the converter 65x90x40 mm. Questions about the design can be asked to the author [email protected]

Power supply "SOFT" LOAD ON THE MAINS When connecting and disconnecting load Interference in the electrical network can often disrupt the normal operation of sensitive electronic devices and electrical systems. The device, the diagram of which is shown in Fig. 1, realizes "soft" load connection and disconnection. \u003d SOFT LOAD IN THE ELECTRIC MAINS Puc.1 When the contacts of the switch SA1 are closed during the charging of capacitor C1 (through the resistor R1), the transistor VT1 gradually opens and the collector current gradually increases to a value determined by the ratio of the resistances of the resistors R1 and R2. Accordingly, the current in the load increases smoothly. When turned off, the capacitor is discharged through the resistor R2 and the base-emitter junction of the transistor. The current gradually decreases to zero. With the values \u200b\u200bof the elements and the power of 200 W indicated in the diagram, the duration of the on process is 0.1 s, and off - 0.5 s. T160 current regulator circuit The voltage losses in this device are relatively small, they are determined by the sum of the forward drop on two diodes and the collector-emitter section of the operating transistor, which is approximately: Uce (B) \u003d 0.7 + R1 * In / h21e Depending on the current load and the current transfer coefficient of the base of the transistor, the resistor R) should be selected so that the voltage drop across the transistor and the power dissipation across it would be maintained in the on state at an acceptable level. \u003d SOFT LOAD IN POWER MAINS Puc. 2 In the version of the device shown in fig. 2, armor against overloads and short circuits is provided. When the current exceeds the set value, the drop ...

For the diagram "Load connection indicator"

Looking for a light switch or an outlet in the dark is not a pleasant business. Household lighting switches equipped with indicators highlighting their location appeared on sale. By slightly improving the circuit, such an indicator can be turned into a load connection indicator. load (PPI) is a device built into the socket and indicating the presence of a contact between the inserted mains plug from any household appliance and the socket. The indicator is especially convenient if the connected devices do not have their own network indicator. The PSI is also useful for radio-electronic products, in which the indicators of inclusion are in the secondary power circuit, since it allows you to check their input circuits. The PSI consists of: - a current sensor load on diodes VD2 ... VD6; - L-shaped filter R1-C1; - a key on a field-effect transistor VT1; - an indication unit on the elements VD9, VD10, R2, HL1. If the load is not connected to the XS1 socket, then no current flows through the VD1 ... VD6 diodes, the storage capacitor C1 is discharged and the field-effect transistor VT1 is closed. Power regulator on ts122 25 The drain current VT1 is zero, the HL1 indicator does not light. load to XS1 socket current load flows through a counter-parallel connected diode VD1 and a chain of diodes VD2 ... VD6. Negative half-waves of the mains voltage pass through VD1. and positive ones - through VD2 .. .VD6. The voltage drop across the diodes VD2 ... VD6 through the resistor R1 enters the storage capacitor C1 and charges it to a value exceeding the cutoff voltage of the field-effect transistor VT1. Transistor VT1 opens, and current flows through its source-drain channel, resistor R2, LED HL1 and diode VD9. The HL1 LED glows dazzlingly, indicating that the load is connected. Resistor R2 is a current-limiting diode, the VD9 diode prohibits the flow of current through the load during reverse half-cycles of the mains voltage. Diode VD10 protects HL1 from reverse voltage ....

For the scheme "Simple power regulator"

The inductive load in the power regulator circuit imposes strict requirements on the triac management schemes - the synchronization of the management system must be carried out directly from the mains, the signal must have a duration equal to the conduction interval of the triac. The figure shows a diagram of a regulator that meets these requirements in which a combination of a dinistor and a triac is used.The time constant (R4 + R5) C3 determines the lag angle of the firing of the dynistor VS1 and therefore the triac VS2. By moving the slider of the variable resistor R5, the power consumed by the load is regulated. Capacitor C2 and resistor R2 are used to synchronize and ensure the duration of the management signal. Capacitor C3 is recharged from C2 after switching, since at the end of each half-cycle it has a voltage of reverse polarity. To protect against interference created by the regulator, two Filters R1C1 are introduced into the supply circuit and R7C4 - into the load circuit. To set up the device, you need to put the resistor R5 in the position of maximum resistance and the resistor R3 to set the minimum power at the load Capacitors C1 and C4 of the K40P-2B type for 400 V capacitors C2 and SZ of the K73-17 type for 250 V The diode bridge VD1 can be replaced with diodes KD105B Switch SA1 designed for a current of at least 5 A. V.F. Yakovlev, Shostka, Sumy region. ...

For the scheme "Telephone holding device"

TelephonyThe device of holding the telephone line The proposed device performs the function of holding the telephone line ("HOLD"), which allows during an hour of conversation to put the receiver on the hook and go to a parallel telephone set. The device does not overload the telephone line (TL) and does not create interference in it. At the hour of triggering, the caller hears a musical splash screen. The diagram of the telephone line holding device is shown in the figure. A rectifier bridge based on VD1-VD4 diodes ensures the correct polarity of the device supply, regardless of the polarity of its connection to the TL. Switch SF1 is connected to the hook of the telephone set (SLT) and closes when going off-hook (that is, it locks the SB1 button while on-hook). If you need to switch to a parallel TA during an hour of a conversation, press the SB1 button shortly. In this case, relay K1 is triggered (contacts K1.1 close, and contacts K1.2 open), an equivalent is connected to the TL load (circuit R1R2K1) and the TA from which the conversation was conducted is turned off. T160 current regulator circuit Now you can put the tube on the lever and go to the parallel TA. The voltage drop at the equivalent is 17 V. When the tube is lifted on the parallel TA, the voltage in the TL drops to 10 V, the K1 relay is disconnected and the equivalent is disconnected from the TL. Transistor VT1 must have a transmission ratio of not less than 100, while the amplitude of the ac voltage of the audio frequency, issued in the TL, reaches 40 mV. As a musical synthesizer (DD1), an UMC8 microcircuit is used, in which two melodies and an alarm clock are "protected". Therefore, pin 6 ("melody selection") is connected with pin 5. In this case, the first melody is played once, and then the second endlessly. As SF1 m ...

For the scheme "STABLE CURRENT GENERATOR"

STABLE CURRENT GENERATOR Stable current generators are usually called devices. the output current of which is practically independent of the load resistance. It can find application, e.g. in ohmmeters with a linear scale. In fig. 1 shows a schematic diagram of a stable current generator based on two silicon transistors. The magnitude of the collector current of the transistor V2 is determined by the ratio Ik \u003d 0.66 / R2.Puc.1 For example, when R2 is 2.2 k0m. the collector current of the transistor V2 will be equal to 0.3 mA and remains practically constant when the resistance of the resistor Rx changes from 0 to 30 k0m. If necessary, the DC current value can be increased to 3 mA, for this the resistance of the resistor R2 must be reduced to 180 Ohm. A further rise in the current while maintaining a high stability of its value both with a change in load and with an increase in temperature can only be with the use of a three-transistor generator shown in Fig. 2. In this case, the transistors V2 and V3 should be of average power, and the voltage of the second power supply should be 2 ... 3 times higher than the supply voltage of the transistors V1, V2. The resistance of the resistor R3 is calculated according to the above formula, but is additionally corrected taking into account the spread in the characteristics of the transistors. Fig. 2 "Elektrotehnicar" (SFRY), 1976, N 7-8 From the editor. VS 108 transistors can be replaced by KT315G. VS107 -KT312B, BD137 - KT602B or KT605B, 2N3055 - KT803A ....

For the scheme "TRANSISTOR UMZCH ON THE WAY TO PERFECTION"

AUDIO equipment TRANSISTOR UMZCH ON THE WAY TO PERFECTION Petrov, Mogilev Usually, considering the work of the UMZCH, it is assumed that its load is purely active. However, a loudspeaker, moreover with anti-aliasing filters, is a complex complex load. When operating on a complex load, the resulting phase shift between the voltage and current at the output of the amplifier leads to the fact that, with sinusoidal input signals, the load line turns into an ellipse. Operating point positions (load curve) for reactive load the output characteristics of the triode and transistor with amplification of the harmonic signal are shown in Figs 1 and 2, respectively. As can be seen from Fig. 1, the output characteristics of the triode are almost ideal for a complex load, which is an AC. The favorable spectrum of harmonics (no higher than the fifth) and high linearity largely determine the "softness" of the sound of tube amplifiers. Radio amateur converter circuits At the same time, a single-ended transistor amplifier is completely unsuitable for working on a loudspeaker, because On the one hand, the line enters the region of limited permissible dissipation power on the collector (shaded region, above the hyperbola), on the other - into nonlinear regions at small Uke. The transverse size of the load curve ellipse depends on inductive component of the load, and longitudinal - from the active. When amplifying impulse signals, for example, of the "meander" type, the line load is a parallelogram, which further exacerbates the situation. The amplitude of the voltage jump at the moment of switching (due to the EMF of self-induction) depends on the ratio of the signal time constant To to the time constant load T \u003d L / R ...

Triac power controllers operate using phase control. They can be used to change the power of various electrical devices operating using alternating voltage.

Appliances include electric incandescent lamps, heaters, AC motors, transformer welders, and many others. They have a wide range of adjustment, which gives them a wide range of applications, including in everyday life.

Description and working principle

The operation of the device is based on the regulation of the triac turn-on delay when the mains voltage crosses zero. The triac at the beginning of the half-cycle is in the closed position. After the voltage of the positive half-wave rises, the capacitor is charged with a phase shift from the mains voltage.

This shift determines the values \u200b\u200bof the resistance of resistors P1, R1, R2, and the capacitance of the capacitor C1. When the threshold value is reached on the capacitor, the triac is turned on. It becomes conductive, letting in voltages, thereby shunts the circuit with resistors and capacitors. When the half-cycle passes through 0, the triac turns off.

Then, when the capacitor is charged, it opens again with a negative voltage wave. This operation of the triac is possible due to its structure. It has five semiconductor layers with a gate electrode. That gives him the ability to swap the anode with the cathode. Simply put, it can be represented in the form of two thyristors with an anti-parallel connection.

Application area

Triac power controllers have found their application not only in everyday life, but also in many industries. In particular, they successfully replace bulky relay control circuits. They help to establish optimal currents in automatic welding lines, and in many other industries.

As for the use of these devices in everyday life, its use is very diverse. From regulating the voltage to the incandescent lamps, to regulating the fan speed. In a nutshell, the range is so varied that it is difficult to describe.

Types of triac power regulators

Speaking about these devices, it should be noted that they all work according to the same principle. Their main difference is the power for which they are designed. The second difference will be the control scheme. Some types of triac may require more fine tuning of the control signals. Control can be very diverse, from a capacitor and a pair of resistors to a modern microcontroller.

Scheme

Many different designs can be used in power controllers. The simplest scheme is the use of a variable resistor, and the most complex modern microcontroller. If you use it at home, then you can stop at the simplest one.

It will be enough for most needs. In addition to dimming, the regulator is often used for. Those who love to do electrical engineering at home need to adjust the temperature of the soldering iron.

It is inconvenient to do this using variable resistors, plus there are large losses of electricity. The best solution would be to use a triac regulator.

How to assemble a regulator

Let's take the simplest schematic diagram for assembly. This circuit uses a VD2 triac - VTB 12-600V (600 - 800 V, 12 A), resistors: R1 - 680 kΩ, R2 - 47 kΩ, R3 - 1.5 kΩ, R4 - 47 kΩ. Capacitors: C1 - 0.01 mF, C2 - 0.039 mF.

To assemble such a scheme with your own hands, you will need to do certain actions in the correct order:

1. You must purchase all the parts from the list above.
2. The second step will be the development of the printed circuit board. When developing, it should be taken into account that some of the parts will be carried out by surface mounting. And some of the parts will be installed directly into the board.
3. The creation of the board begins with drawing a drawing with the location of parts and contact paths between parts. Then the drawing is transferred to the board blank. When the drawing is transferred to the board, then everything goes on according to a well-known method. Etching the board, drilling holes for parts, tinning the tracks on the board. Many people use modern computer programs such as Sprint Layout to get a picture of the board, but if you have them there is nothing to worry about. In this case, we have a small diagram. It can be done manually.
4. When the board is ready, we insert the necessary radio parts into the prepared holes, shorten the length of the contacts with pliers to the required one and start soldering. To do this, warm up the contact point on the board with a soldering iron, bring the solder to it, when the solder spreads over the surface at the contact point, remove the soldering iron, let the solder cool. In this case, all parts must remain in place, not move. Safety precautions must be observed when soldering. First of all, you need to beware of burns, they can be caused by contact with a soldering iron, or splashes of hot solder or flux. You should have clothing that protects all areas of the body as much as possible. And to protect your eyes, you must wear safety glasses. The place of soldering should be in a ventilated area, since corrosive gases may appear during operation.
5. The final stage of assembly will be placing the resulting board in the box. Which box to choose will directly depend on the type of your regulator. In the case of our circuit, a box the size of a plastic socket will suffice. A small number of parts, the largest of which is a variable resistor, take up little space and fit into a small space.
6. The last step is to check and configure the device. To do this, you need a measuring device to control the voltage, and a device for the load, in our case, a soldering iron. Turning the knob of the regulator, it is necessary to investigate how smoothly the voltage at the output changes. If necessary, you can make marks near the adjustment resistor.

Price

The market is replete with a large number of offers at various price levels. The price of triac power controllers is primarily influenced by several parameters:

1. Product power, the more powerful the power, the more expensive your device will be.
2. The complexity of the control circuit, in the simplest circuits, the main cost lies with the triacs. In complex control schemes where microcontrollers are used, the price can rise because of them. They provide additional opportunities, respectively, at a higher price. So the regulator on a resistor with a voltage of 220 V, a power of 2500 W. costs 1200 rubles, and on a microcontroller with the same parameters 2450 rubles.
3. Manufacturer's brand. Sometimes you can pay 50% more for a promoted brand.

Now you can find power regulators assembled according to various schemes. Each of them will have their own advantages and disadvantages. Modern regulators are divided into two types, microprocessor and analog. Analog controllers can be classified as economy class systems. They have been known since the times of the USSR, are simple to perform and cheap. Their main drawback is the constant control of the owner, or operator.

Let's give a simple example, you need to have a voltage of 170 V at the output. When you set this voltage, the supply voltage was 225 V, and now let's imagine that the input voltage has changed by 10 V, and the output voltage will change accordingly.

If the magnitude of the output voltage affects the process, problems may arise. In addition to the supply voltage drop, the output can be influenced by the parameters of the regulator itself. Since the capacitance of the capacitor changes over time, the ambient humidity can affect the variable resistor, it is impossible to achieve stable operation.

Microprocessor-based regulators do not have this problem. They have a feedback that allows you to quickly adjust the control signal.

One of the important points of long-term operation will be repair and service. Microprocessor controllers are complex products, and specialized service centers will be required to repair them. Analog regulators are easier to repair. It can be made by any radio amateur at home.

You can make the final choice on a triac power regulator after studying the conditions for its operation. When you don't need great output precision, it makes sense to opt for an analog instrument while saving money. When accuracy is needed in the output, do not save money, buy a microprocessor device.

A small semiconductor device "triac", or a symmetrical trinistor (thyristor), hides behind its complex name a fairly simple principle of operation, comparable to the operation of a door in a subway. Ordinary thyristors can be compared to a simple door: if you close it, there will be no passage. And such a door works in one direction. Triacs work in both directions. That is why the comparison with a door in the subway: wherever it is not pushed, it comes off and lets the flow of passengers in any direction.

The double-sided action of the triac is due to its special structure. Its cathode and anode are able, in a sense, to swap places and perform the functions of each other, passing current in the opposite direction. This is possible due to the fact that the triac has 5 semiconductor layers and a gate electrode.

For ease of understanding the physical processes occurring in the triac, it can be represented as two anti-parallel connected thyristors.

Triacs are used in various circuits as contactless keys and have a number of advantages over contactors, relays, starters and similar electromechanical elements:

• triacs are durable, practically indestructible;
• where there is electromechanics, there are restrictions on the switching frequency, wear, and the corresponding risks and problems, and such nuances do not arise with semiconductors;
• complete absence of sparking and associated risks;
• the ability to carry out switching at moments of zero mains current, which reduces interference and the impact on the accuracy of the circuits.

Diagram of a simple power regulator on a triac

Most often, triacs are used in power control circuits. One of the simplest and most common power regulators on the KU208G triac is shown below.

As can be seen in the figure, the power circuit of the circuit is equipped with a KU208 triac, and its control circuit includes only one element - a P416A transistor. The adjustment of the device operation is reduced to the selection of the value of the resistor R1 and proceeds in the following sequence:

• set the slider of the resistor R4 to the lower position;
• instead of resistor R1, install a variable resistor with a resistance of 150 ohms;
• set the variable resistor to the maximum position;
• connect an AC voltmeter to the load;
• connect the device to the network.

In order to connect correctly, it must correspond to the pre-selected installation location and the number of devices to be connected. At the same time, it is very important to check the correct operation of the lighting devices and adjust the corresponding parameters of the sensor.

This equipment, due to its technological qualities, is gaining more and more popularity when arranging lighting at home. After reading, you can understand the principle of operation of various motion sensors, which will help in the further choice of a suitable device for your home.

Next, you need to rotate the motor of the resistor R1 and monitor the voltage across the load: it is necessary to ensure that it stops increasing. In the position found, it is necessary to measure the resistance of the variable resistor, and accordingly the resistance of the resistor R1 will be set. It is with this rating that it will be necessary to install a constant resistor R1 in the circuit in place of the variable sample.

Feedback in triac control circuits

To control the power (temperature) of heating elements of various devices, rotation speeds of motors, etc. recently, despite the higher cost than electromechanics, a triac power regulator has been used. The need to use an additional radiator for such a circuit is a small fee in exchange for the absence of risks of sparking, a long period of uptime, and the stability of the output parameters.

Such a control scheme is common in devices such as soldering irons, electric drills, etc.

Below is an example of another triac power control circuit. This is a circuit for regulating the speed of an industrial sewing machine motor.


The circuit is assembled on a triac VS1, rectifier valves VD1 and VD2, and a variable resistor R3 in the control circuit. The feature and key distinguishing feature of such a scheme is feedback. A triac that carries current in both directions is the best solution for control circuits where this feedback is required.

When choosing the type of protective devices, first of all, their technical installation capabilities are taken into account in the aggregate of individual preferences. This is the decisive factor in solving the question:? Only by studying the features of their work, it is possible to achieve the safe functioning of the household electrical network.

Applying residual current devices at home, you need to know the features of its various types - in order to be correct, and also to study the installation diagrams - in order to be correct.

Comparing with outdated switching technologies, one can identify another clear advantage of power control circuits on triacs - this is the ability to provide high-quality feedback and, accordingly, adjust the feedback operation.

Features and benefits of the scheme:

1. In this case, implemented load feedback, which allows increasing the engine speed and ensuring smooth uninterrupted operation of the machine in the event of an increase in load forces. In this case, all operations are performed by the circuit automatically. No arcing or overheating occurs. As you can see from the figure, there is no heat sink.

This scheme is regulation of active power of devices... The use of such schemes in light intensity control systems is not recommended. For a number of reasons, the lights will flash violently.

2. Triac switching in this circuit occurs strictly at the moments of transition through "0" of the mains voltage, so one can declare the complete absence of interference from the regulator.
3. Actuated, i.e. the triac turns on from a positive pulse arriving at the control electrode at a positive voltage at the anode, or from a negative pulse at a negative position at the cathode. The cathode and anode, given the features of the bidirectional operation of the triac, are conditional here. depending on the work in different directions, they will change functions.
4. As a source of impulses for controlling the triac, it can be used bidirectional dinistor... Or, for reasons of reducing the cost of the circuit, you can connect a pair of ordinary dinistors in an anti-parallel direction. To provide a wider range of regulation of low voltages, dinistors of the KNR102A type will be the best choice. Another option for a key element is an avalanche transistor.
5. Regulation of active and reactive power have some distinctive features. Driving inductive loads requires an RC circuit (parallel to the triac). This will keep the rate at which the voltage at the anode of the triac increases.

Triac power regulator video