To control some types of household appliances (for example, a power tool or a vacuum cleaner), a power regulator based on a triac is used. You can learn more about the operating principle of this semiconductor element from the materials posted on our website. In this publication we will consider a number of issues related to triac circuits for controlling load power. As always, let's start with theory.
Let us recall that a triac is usually called a modification of a thyristor that plays the role of a semiconductor switch with a nonlinear characteristic. Its main difference from the basic device is two-way conductivity when switching to the “open” operating mode, when current is supplied to the control electrode. Thanks to this property, triacs do not depend on voltage polarity, which allows them to be used effectively in circuits with alternating voltage.
In addition to the acquired feature, these devices have an important property of the base element - the ability to maintain conductivity when the control electrode is disconnected. In this case, the “closing” of the semiconductor switch occurs when there is no potential difference between the main terminals of the device. That is, when the alternating voltage crosses the zero point.
An additional bonus from this transition to the “closed” state is the reduction in the amount of interference during this phase of operation. Please note that a regulator that does not create interference can be created under the control of transistors.
Thanks to the properties listed above, it is possible to control the load power through phase control. That is, the triac opens every half-cycle and closes when crossing zero. The delay time for turning on the “open” mode, as it were, cuts off part of the half-cycle, as a result, the shape of the output signal will be sawtooth.
In this case, the signal amplitude will remain the same, which is why it is incorrect to call such devices voltage regulators.
Let's give a few examples of circuits that allow you to control load power using a triac, starting with the simplest.
Figure 2. Circuit diagram of a simple triac power regulator powered by 220 V Designations:
With the help of dinistor DN1, the circuit D1-C1-DN1 is closed, which moves DN2 to the “open” position, in which it remains until the zero point (completion of the half-cycle). The moment of opening is determined by the time of accumulation on the capacitor of the threshold charge required to switch DN1 and DN2. The rate of charge C1 is controlled by the chain R1-R2, the total resistance of which determines the moment of “opening” of the triac. Accordingly, the load power is controlled through a variable resistor R1.
Despite the simplicity of the circuit, it is quite effective and can be used as a dimmer for filament lighting or a soldering iron power regulator.
Unfortunately, the above circuit does not have feedback, therefore, it is not suitable as a stabilized speed controller of a commutator electric motor.
Feedback is necessary to stabilize the speed of the electric motor, which can change under the influence of load. You can do this in two ways:
The latter option is much easier to implement, but requires slight adjustment to the power of the electric machine used. Below is a diagram of such a device.
Designations:
This circuit ensures a smooth start of the electrical installation and protects it from overload. Three operating modes are allowed (set by switch S1):
Setting up the circuit comes down to selecting resistance R6; it is calculated depending on the power of the electric motor using the following formula: . For example, if we need to control a 1500 W motor, then the calculation will be as follows: 0.25 / (1500 / 240) = 0.04 Ohm.
To make this resistance, it is best to use nichrome wire with a diameter of 0.80 or 1.0 mm. Below is a table that allows you to select the resistance R6 and R11, depending on the engine power.
The above device can be used as a speed controller for motors of power tools, vacuum cleaners and other household equipment.
Those who try to control an inductive load (for example, a welding machine transformer) using the above circuits will be disappointed. The devices will not work, and the triacs may fail. This is due to a phase shift, which is why during a short pulse the semiconductor switch does not have time to switch to the “open” mode.
There are two options to solve the problem:
The first option is the most optimal. Here is a diagram where this solution is used.
As can be seen from the following figure, which shows oscillograms of the main signals of the power regulator, a packet of pulses is used to open the triac.
This device makes it possible to use regulators on semiconductor switches to control an induction load.
At the end of the article, we will give an example of a simple power regulator. In principle, you can assemble any of the above circuits (the most simplified version was shown in Figure 2). For this device it is not even necessary to make a printed circuit board; the device can be assembled by surface mounting. An example of such an implementation is shown in the figure below.
This regulator can be used as a dimmer, and can also be used to control powerful electric heating devices. We recommend choosing a circuit in which a semiconductor switch with characteristics corresponding to the load current is used for control.
Due to the electrical problem, people are increasingly buying power regulators. It is no secret that sudden changes, as well as excessively low or high voltage, have a detrimental effect on household appliances. In order to prevent damage to property, it is necessary to use a voltage regulator that will protect electronic devices from short circuits and various negative factors.
Nowadays on the market you can see a huge number of different regulators both for the whole house and for low-power individual household appliances. There are transistor voltage regulators, thyristor, mechanical (voltage adjustment is carried out using a mechanical slider with a graphite rod at the end). But the most common is the triac voltage regulator. The basis of this device are triacs, which allow you to react sharply to voltage surges and smooth them out.
A triac is an element that contains five p-n junctions. This radio element has the ability to pass current both in the forward and reverse directions.
These components can be observed in various household appliances, from hair dryers and table lamps to soldering irons, where smooth adjustment is necessary.
The principle of operation of a triac is quite simple. This is a kind of electronic key that either closes or opens doors at a given frequency. When the P-N junction of the triac is opened, it passes a small part of the half-wave and the consumer receives only part of the rated power. That is, the more the P-N junction opens, the more power the consumer receives.
The advantages of this element include:
In connection with the above advantages, triacs and regulators based on them are used quite often.
This circuit is quite easy to assemble and does not require many parts. Such a regulator can be used to regulate not only the temperature of the soldering iron, but also conventional incandescent and LED lamps. This circuit can be used to connect various drills, grinders, vacuum cleaners, and sanders, which initially came without smooth speed control.
You can assemble such a 220V voltage regulator with your own hands from the following parts:
The circuit has been tested and works quite stably under different types of load..
There is another scheme for a universal power regulator.
An alternating voltage of 220 V is supplied to the input of the circuit, and 220 V DC is supplied to the output. This scheme already has more parts in its arsenal, and accordingly the complexity of the assembly increases. It is possible to connect any consumer (DC) to the output of the circuit. In most houses and apartments, people try to install energy-saving lamps. Not every regulator can cope with smooth adjustment of such a lamp; for example, it is not advisable to use a thyristor regulator. This circuit allows you to easily connect these lamps and make them into a kind of night lights.
The peculiarity of the scheme is that when the lamps are turned on to minimum, all household appliances must be disconnected from the network. After this, the compensator in the meter will work, and the disk will slowly stop, and the light will continue to burn. This is an opportunity to assemble a triac power regulator with your own hands. The values of the parts needed for assembly can be seen in the diagram.
Another entertaining circuit that allows you to connect a load of up to 5A and a power of up to 1000W.
The regulator is assembled on the basis of the BT06−600 triac. The operating principle of this circuit is to open the triac junction. The more the element is open, the more power is supplied to the load. There is also an LED in the circuit that will let you know whether the device is working or not. List of parts that will be needed to assemble the device:
Triacs and thyristors are successfully used as starters. Sometimes it is necessary to start very powerful heating elements, to control the switching on of powerful welding equipment, where the current strength reaches 300-400 A. Mechanical switching on and off using contactors is inferior to a triac starter due to the rapid wear of the contactors; moreover, when switching on mechanically, an arc occurs, which also has a detrimental effect on contactors. Therefore, it would be advisable to use triacs for these purposes. Here is one of the schemes.
All ratings and parts list are shown in Fig. 4. The advantage of this circuit is complete galvanic isolation from the network, which will ensure safety in the event of damage.
Often on a farm it is necessary to perform welding work. If you have a ready-made inverter welding machine, then welding does not present any particular difficulties, since the machine has current regulation. Most people do not have such a welding machine and have to use a regular transformer welding machine, in which the current is adjusted by changing the resistance, which is quite inconvenient.
Those who tried to use a triac as a regulator will be disappointed. It will not regulate power. This is due to a phase shift, which is why during a short pulse the semiconductor switch does not have time to switch to the “open” mode.
But there is a way out of this situation. You should apply a pulse of the same type to the control electrode or apply a constant signal to the UE (control electrode) until it passes through zero. The regulator circuit looks like this:
Of course, the circuit is quite complicated to assemble, but this option will solve all problems with adjustment. Now you won’t need to use cumbersome resistance, and you won’t be able to make very smooth adjustments. In the case of a triac, fairly smooth adjustment is possible.
If there are constant voltage drops, as well as low or high voltage, it is recommended to purchase a triac regulator or, if possible, make a regulator yourself. The regulator will protect household appliances and also prevent damage.
Such a simple, but at the same time very effective regulator can be assembled by almost anyone who can hold a soldering iron in their hands and even slightly read the diagrams. Well, this site will help you fulfill your desire. The presented regulator regulates power very smoothly without surges or dips.
We can make an excellent power regulator up to three kilowatts ourselves, practically from rubbish, but it will work no worse, and in some places even better, than the “branded” ones. No power surges, dips or other troubles. At the end of the article there will be a video clip in which you can see with your own eyes that this is really the case.
Power regulator up to three kilowatts.
The controller can smoothly change the illumination of incandescent and dimmable LED lamps within a wide range from zero to 100%.
To begin installing the device, let’s assemble the parts.
At the bottom of the photo there are DB3 samples - 3 pieces
The development board greatly facilitates and speeds up the installation of electronic devices. No need to bother with manufacturing and drilling printed circuit boards. You simply insert the radio components into the prepared holes, solder them, connect them according to the diagram with jumpers and you’re done.
All capacitors and dinistors can be removed from old energy-saving lamps. Not all lamps have capacitors with the required ratings and dinistors, so you need to look for them. Dinistors in different housings are at the bottom of the second photo (so you have an idea of their appearance), and on their housings they say DB3 (you can read them with a magnifying glass).
I took the potentiometer from an old, Soviet TV, but any other one with the indicated values will do.
The radiator is from a computer unit, but it needs to be selected depending on the planned load that you are going to manage. Up to 300 watts, a radiator is not needed at all, and the higher the load, the more massive the radiator. The size of the radiator also depends on the nature of the load, so selection is an individual matter, but the larger the radiator, the better the operating mode of the triac and it will work longer without accidents. So don't skimp and bet more.
There are resistors everywhere, in any equipment, so choosing them won’t be a big problem. You can also buy it in China. 600 resistors of different denominations “set” cost about 150 rubles, including delivery, so it’s easier to buy than to bother with searching and unsoldering from blocks.
You can take any terminals for connecting power and load that you find, but you can do without them altogether, the question is the ease of use of this device in operation.
The device diagram looks like this.
The R4 – C3 chain is protection against radio interference and you can remove it, but your neighbors may beat you up for it if they catch you.
Schematic diagram of the power regulator.
Now let's start assembling.
We place the parts on a breadboard; in my opinion, it’s faster, more convenient, and looks good. Soldering must be done as efficiently as possible and preferably slowly.
I haven’t seen high-quality tin from China, so use any other one.
We coat the triac with heat-conducting paste, but not thickly.
Solder it.
It is better to solder the parts one by one, one at a time, as they are installed.
The jumpers (indicated in red in the diagram) are made with copper wire of a higher cross-section, depending on the load power. At 3 kilowatts - 2.5 square millimeters will be, with a margin, just right. I plan to control the speed of the drill at 800 watts, and the wire was 1.5 mm, of course, also with a margin, but as they say, a margin…. . And it will work better.
The "third hand" makes the work much easier.
You need to constantly check the diagram when installing parts.
The scheme is simple, but attentiveness will not be superfluous.
The power part requires very careful soldering.
The use of modern circuit technology using simple original solutions on traditional element base and on new small-sized microcircuits allows us to produce compact and easy-to-use high power regulators. This article describes several simple designs of load power regulators up to 5 kW, which can be easily made from available parts.
Electronic power regulatorsloads are currently widely used in industry and everyday life forsmooth regulation of the rotation speed of electric motors, temperature of heating devices, intensity of room lighting with electric lamps, setting the required welding current, adjusting the charging current of batteries, etc. Previously, bulky transformers and autotransformers with stepwise or smooth switching of the turns of their windings working on the load were used for this. Electronic regulators are more compact, easy to use and light in weight with significantly greater power. Basically, the executive elements of electronic AC power regulators are: thyristor, triac and optothyristor, the latter is controlled through an optocoupler built into it, which eliminates the galvanic connection between the control circuit and the power supply network.
Power regulation by these elements is based on changing the switching phase of the triac in each half-wave of the sinusoidal voltage by the control circuit. As a result, the voltage waveform at the load is “cuts” of half-waves of a sinusoid with steep fronts (Fig. 1).In this case, the voltage waveform on the power regulator itself has the form shown in Fig. 2. This signal form has a wide range of harmonics, which, propagating through electrical wiring, can interfere with electronic devices: televisions, computers, sound-reproducing equipment, etc. In this regard, RC or RLC filters are installed at the network inputs of such power regulators.
Fig.1
In practice, all currently produced electronic household devices and computers have their own built-in network filters, thanks to which interference from power regulators may not affect the operation of these electronic devices. The author tested various power regulators without their own network filters in rooms where a TV,
Fig.2
Computer, FM receiver and DVD player with UMZCH No interference was observed on this equipment, but this does not mean that filters are not needed at all. These power regulators can interfere with the electronic equipment of neighbors in the entrance. Practical studies of the propagation of interference along electrical wiring in adjacent rooms using an oscilloscope showed that when regulating load power up to 2 kW, an RC filter is sufficient, which is confirmed by circuit diagrams of industrial products. For higher power regulators, it is necessary to connect an LC filter after the RC filter,
Fig.3
Fig.4
The schematic diagram of the mains filter for an industrial power regulator up to 4 kW type RT-4 UHL4.2 220V-1 P30 is shown in Fig. 3,installation of the regulator - in Fig. 4. Each coil contains 90 turns of PEV-2 wire with a diameter of 1.5 mm, wound in two layers on a frame, inside of which there is a ferrite core with a permeability F600 with a diameter of 8 mm. The inductance of the coil is 0.25 mH. Power regulators without filters can be used in garages, individual utility rooms, cottages, etc., that is, away from neighbors. If the power regulator is a separate product and is intended to connect loads of different power, it is important for users to know that with the same position of the regulator knob, different loads will have different voltages. For this reason, the power regulator must be set to zero before connecting the load. If necessary, you can control the voltage on the load using a separate or built-in voltmeter.
There are many different circuits of electronic load power regulators with almost identical functions on the Internet and electrical magazines, but there are also other circuit solutions, for examplenon-interfering regulators. These regulators produce bursts of sinusoidal currents, the duration of which regulates the power in the load. The circuits of such regulators are relatively complex and can be used in some special cases. The use of such regulators in industry has not been encountered. The vast majority of power regulators are built on the principle of phase control of current in the load. The main difference is the control circuits for thyristors and triacs. The power part consists of practically three options: a thyristor in the diagonal diode bridge, two back-to-back thyristors and a triac. Control circuits are various options based on transistors, microcircuits, dinistors, gas-discharge devices, unijunction transistors, etc., some of which are given in [1-6]. Such circuits contain many parts and are relatively complex to manufacture and set up.
Thyristor regulators
The simplest and most widely used power regulator was a thyristor regulator connected to the diagonal of the diode bridge and with a simple control circuit (Fig. 5). The principle of operation of this regulator is very simple: while capacitor C2 is charged through R2 and R4, the thyristor is locked, when the unlocking voltage is reached at C2, the thyristor opens and passes current into the load, and C2 is quickly discharged through a low
Fig. 5 power regulator on a thyristor
open thyristor resistance. When the sinusoidal network voltage passes through zero, the thyristor turns off and waits for a new increase in the voltage on C2. The more time C2 is charged, the less time the thyristor is in the open state and the less current in the load. The smaller the value of R4, the faster C2 is charged and the more current is passed into the load. The advantage of this circuit is that, regardless of the parameters of a working thyristor, the positive and negative current pulses in the load are always symmetrical, as well as the presence of only one thyristor, which were in short supply when they appeared. The disadvantage is the presence of four powerful diodes, which, together with the thyristor and coolers, significantly increases the dimensions of the regulator. Power regulators based on back-to-back thyristors are more compact and twice as powerful. Using two KU202N thyristors with a simple control circuit, a load power regulator of up to 4 kW is obtained, which the author has been using for a long time in a high-power heater.
The schematic diagram of such a regulator with a line filter is shown in Fig. 6. The disadvantage of such circuits is the asymmetry of positive and negative current pulses in the load when the thyristor parameters vary.
Fig.6
The asymmetry manifests itself in the initial stage of opening the thyristors. For heating devices and power tools with commutator motors, this asymmetry does not play a practical role, and lighting devices, when their brightness decreases, begin to blink, since pulses of some polarity disappear altogether. To eliminate this drawback, it is necessary to select thyristors with identical parameters for the opening current and holding current of thyristors from a technological direct current source at the appropriate load, or by selecting a second thyristor based on the absence of lamp blinking at minimum filament heat.
One of the varieties of thyristors are optothyristors, to control which, when connected in back-to-back parallel mode, the control principle of the circuit in Fig. 5 can be applied.with separation of positive and negative control pulses using diodes or dinistors.
A practical schematic diagram of such a load power regulator up to 5 kW is shown in Fig. 7.This regulator is used by the author to adjust the welding current and operating modes of other powerful electrical devices. The power regulator is equipped with a dial indicator of voltage at the load, which increases the convenience of its operation. In Fig.8a dial indicator (pos. 1) is visible, on which parts of its rectifier and filter are glued. The regulator does not have a surge protector, as it is used either in the country house or in the garage. If necessary, you can use a filter, the diagram of which is shown in Fig. 3.
Fig. 7, diagram of a power regulator using optothyristors
Fig.8
Regulators on triacs
Of particular interest are modern circuits of power regulators using triacs. Traditional triac control circuits contain relatively many parts, as can be clearly seen on the industrial regulator circuit board shown in Fig. 4.For example, a microcircuitKR1167KP1B outputs control pulses to the control electrode of the triac, shown on the oscillogram (Fig. 9).A schematic diagram of a power regulator using this microcircuit, common among Zaporozhye electricians, is shown in Fig. 10. This heatsinkless power regulator for VS1 can handle loads up to 200W
Fig.9
(Fig. 11), and with a radiator with an area of at least 100 cm 2 - up to 2 kW. It turned out that this scheme can be further simplified without loss of quality. A simplified diagram of a regulator with this microcircuit is shown in Fig. 12.When using serviceable parts, these circuits do not require adjustment.
Fig. 10, power regulator circuit using triacs
In the manufacture of regulators for bedside lamps, it turned out that some triacs and microcircuits have defects that affect the symmetry of the pulses and, accordingly, the uniformity of the lamp glow adjustment, and even lead to their
Fig.11
blinking. Resoldering parts on a printed circuit board is an unpleasant procedure and leads to its damage. In this regard, a test board was made according to the diagram in Fig. 10(without R1 and C1) with a socket for a single-row microcircuit, which solved these problems. Regulators are soldered to contacts 1-2 of the printed circuit board.
Rice. 12
polishing resistor R5. An incandescent lamp is connected as a load. Before installing parts for testing, the board must be disconnected from the power supply.
Based on the diagram in Fig. 11, a portable process controller for various works was manufactured. Installation of parts is shown in the photoat the beginning of the article (the bottom cover is removed). The circuit is assembled in an aluminum case, which also serves as a triac cooler, isolated from the case by a mica gasket and a special insulating washer. After attaching the triac, it is imperative to check the insulation resistance between its anode and the case, which must be at least 1 MOhm. This regulator, when tested for two hours, worked normally without heating the case to a load of 500 W.
In conclusion, it should be noted that the load power regulators assembled according to the diagrams in Fig. 6 and Fig. 10, tested by long-term operation, are the most optimal in terms of reliability, compactness, simplicity of parts, installation and commissioning. With small variations in thyristor parameters and asymmetry in triac parameters, these regulators can operate on all types of loads of appropriate power, except for lighting devices. Deviations of resistor and capacitor values from those indicated in the diagrams by 10...20% do not affect the operation of the regulators. The above control circuits can also work with more powerful thyristors and triacs in power regulators for loads up to 5 kW. Power regulator according to the diagram in Fig. 12 is recommended for use for lighting devices with a power of up to 100 W without a heat sink. The operation of this regulator for other types of loads has not been tested, but presumably it should not be worse than the regulator assembled according to the diagram in Fig. 10 .
A.N. Zhurenkov
Literature
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2. Karapetyants V. Improvement of the power controller // Radio. - 1986. -№11.
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