After researching sources and a number of sites on the Internet, I simplified the AC voltage stabilizer described in the article. The number of microcircuits was reduced to four, the number of optosimistor switches to six. The principle of operation of the stabilizer is the same as that of the prototype.
Main technical characteristics of the voltage stabilizer:
- Input voltage, V…..135…270
- Output voltage, V. . . .197…242
- Maximum load power, kW………………5
- Load switching or disconnection time, ms…….10
The diagram of the proposed stabilizer is shown in the figure. The device consists of a power module and a control unit. The power module contains a powerful autotransformer T2 and six AC switches, outlined in the diagram with a dash-dotted line.
The remaining parts form the control unit. It contains seven threshold devices: I - DA2.1 R5 R11 R17, II -DA2.2 R6 R12 R18, III - DA2.3 R7 R13 R19, IV - DA2.4 R8 R14 R20, V - DA3.1 R9 R15 R21 , VI - DA3.2 R10 R16 R22, VII -DA3.3 R23. At one of the outputs of the decoder DD2 there is a high level voltage, which causes the corresponding LED to turn on (one of HL1 - HL8).
The powerful autotransformer T2 is connected differently than in the prototype. The mains voltage is supplied to one of the winding taps or to the entire winding through one of the triacs VS1-VS6, and the load is connected to the same tap. With this connection, less wire is consumed on the winding of the autotransformer.
The voltage of winding II of transformer T1 is rectified by diodes VD1, VD2 and smoothed by capacitor C1. The rectified voltage is proportional to the input voltage. It is used both to power the control unit and to measure the input network voltage. For this purpose, it is fed to the divider R1-R3. From the engine of the trimming resistor R2 it goes to the non-inverting inputs of operational amplifiers DA2.1 - DA2.4, DA3.1 - DA3.3. These op amps are used as voltage comparators. Resistors R17-R23 create hysteresis for switching comparators.
The table below shows the limits of change in the output voltage Uout and the logical voltage levels at the outputs of operational amplifiers and the inputs of the DD2 decoder, as well as the turned on LEDs depending on the input voltage Uin without taking into account hysteresis.
The DA1 microcircuit produces a stable voltage of 12 V to power the remaining microcircuits. Zener diode VD3 produces a reference voltage of 9 V. It is supplied to the inverting input of op-amp DA3.3. It is supplied to the inverting inputs of other op-amps through dividers on resistors R5-R16.
When the mains voltage is below 135 V, the voltage on the motor of resistor R2, and therefore on the non-inverting inputs of the op-amp, is less than on the inverting ones. Therefore, the outputs of all op-amps are low. All outputs of the DD1 chip are also low. In this case, a high level appears at output O (pin 3) of decoder DD2. The HL1 LED is on, indicating that the mains voltage is too low. All optosimistors and triacs are closed. No voltage is supplied to the load.
When the network voltage is from 135 to 155 V, the voltage on the motor of resistor R2 is greater than on the inverting input of DA2.1, so its output level is high. The output of element DD1.1 is also high. In this case, a high level appears at output 1 (pin 14) of the DD2 decoder (see table). LED HL1 goes out. The HL2 LED turns on, current flows through the emitting diode of the optocoupler U6, as a result of which the optosimistor of this optocoupler opens. Through an open triac VS6, the mains voltage is supplied to the lower tap in the circuit (pin 6) relative to the beginning of the winding (pin 7) of autotransformer T2. The load voltage is 64...71 V higher than the mains voltage.
With a further increase in the network voltage, it will switch to the next output of autotransformer T2 up in the circuit. In particular, the network voltage from 205 to 235 V is directly supplied to the load through the open triac VS2, as well as to terminals 1-7 of the autotransformer T2.
When the network voltage is from 235 to 270 V, the outputs of all op-amps, except DA3.3, are high, the current flows through the HL7 LED and the emitting diode U1.2. The network voltage is connected through an open triac VS1 to the entire winding of autotransformer T2. The load voltage is 24…28 V less than the mains voltage.
When the mains voltage is more than 270 V, the outputs of all op-amps are at a high level, and the current flows through the HL8 LED, which signals an excessively high mains voltage. All optosimistors and triacs are closed. No voltage is supplied to the load.
The low-power transformer T1 is similar to that used in the prototype, except that its secondary winding contains 1400 turns tapped from the middle. Powerful autotransformer T2 - ready from the industrial stabilizer VOTO 5000 W. Having unwinded the secondary winding and part of the primary, I made new taps, counting from the beginning of the winding (pin 7): pin 6 from the 215th turn (150 V), pin 5 from the 236th turn (165 V), pin 4 from the 257th turn (180 V), pin 3 from the 286th turn (200 V), pin 2 from the 314th turn (220 V). The entire winding (pins 1-7) has 350 turns (245 V).
Fixed resistors - C2-23 and OMLT, trimming resistor R2 - C5-2VB. Capacitors C1 - SZ - K50-35, K50-20. Diodes (VD1, VD2) can be replaced with -, KD243B - KD243Zh.
The microcircuit can be replaced with domestic analogues KR1157EN12A, KR1157EN12B.
The adjustment is performed using LATR. First, switching thresholds are set. To achieve higher installation accuracy, resistors R17-R23, which create hysteresis, are not installed. The powerful autotransformer T2 is not connected. The device is connected to the network via LATR. At the output of the LATR, the voltage is set to 270 V. The slider of the trimming resistor R2 is moved from bottom to top according to the circuit until the HL8 LED turns on. Next, the voltage at the LATR output is set to 135 V. Resistor R5 is selected so that the voltage at the inverting input (pin 2) of the DA2.1 op-amp is equal to the voltage at its non-inverting input (pin 3). Then resistors R6...R10 are sequentially selected, setting switching thresholds of 155 V, 170 V, 185 V, 205 V, 235 V, checking the logical levels with the table. After this, resistors R17-R23 are installed. If necessary, select their resistances by setting the required width of the hysteresis loop. The greater the resistance, the smaller the loop width. Having set the switching thresholds, connect a powerful autotransformer T2, and to it a load, for example, an incandescent lamp with a power of 100...200 W. Check the switching thresholds and measure the voltage across the load. After adjustment, LEDs HL2-HL7 can be removed by replacing them with jumpers.
LITERATURE:
1. Godin A. AC voltage stabilizer. - Radio, 2005, No. 8.
2. Ozolin M. Improved control unit for alternating voltage stabilizer. - Radio, 2006, No. 7.
Often, for safe use of, for example, a TV, usually in rural areas, you need a single-phase voltage stabilizer 220V, which, when the voltage in the electrical network is greatly reduced, produces a rated output voltage of 220 volts at its output.
In addition, when operating most types of consumer electronic equipment, it is desirable to use a voltage stabilizer that does not create changes in the output voltage sine wave. Schemes of similar stabilizers for 220 volts are given in many magazines on radio electronics.
In this article we give an example of one of the options for such a device. The stabilizer circuit, depending on the actual voltage in the network, has 4 ranges of automatic setting of the output voltage. This contributed to a significant expansion of the stabilization limits of 160...250 volts. And with all this, the output voltage is ensured within normal limits (220V +/- 5%).
Description of the operation of a single-phase voltage stabilizer 220 volts
The electrical circuit of the device includes 3 threshold blocks, made according to the principle, consisting of a zener diode and resistors (R2-VD1-R1, VD5-R3-R6, R5-VD6-R6). Also in the circuit there are 2 transistor switches VT1 and VT2, which control electromagnetic relays K1 and K2.
Diodes VD2 and VD3 and filter capacitor C2 form a constant voltage source for the entire circuit. Capacities C1 and C3 are designed to absorb minor voltage surges in the network. Capacitor C4 and resistance R4 are “spark arresting” elements. To prevent self-induction voltage surges, two diodes VD4 and VD7 were added to the circuit in the relay windings when they are turned off.
With perfect operation of the transformer and threshold blocks, each of the 4 regulation ranges would create a voltage range from 198 to 231 volts, and the probable mains voltage could be in the region of 140...260 volts.
However, in reality, it is necessary to take into account the spread of parameters of radio components and the instability of the transformer transformation ratio under different loads. In this regard, for all 3 threshold blocks the output voltage range is reduced in relation to the output voltage: 215 ± 10 volts. Accordingly, the oscillation interval at the input has narrowed to 160...250 volts.
Stages of operation of the stabilizer:
1. When the mains voltage is less than 185 volts, the voltage at the rectifier output is low enough for one of the threshold blocks to operate. At this moment, the contact groups of both relays are located as indicated on the circuit diagram. The voltage at the load is equal to the mains voltage plus the boost voltage removed from windings II and III of transformer T1.
2. If the network voltage is in the range of 185...205 volts, then the zener diode VD5 is in the open state. The current flows through relay K1, zener diode VD5 and resistances R3 and R6. This current is not enough for relay K1 to operate. Due to the voltage drop across R6, transistor VT2 opens. This transistor, in turn, turns on relay K2 and contact group K2.1 switches winding II (voltage booster)
3. If the network voltage is in the range of 205...225 volts, then the zener diode VD1 is already in the open state. This leads to the opening of transistor VT1, which is why the second threshold block and, accordingly, transistor VT2 are turned off. Relay K2 is turned off. At the same time, relay K1 and contact group K1.1 are turned on. moves to another position, in which windings II and III are not involved and therefore the output voltage will be the same as at the input.
4. If the network voltage is in the range of 225...245 volts, the zener diode VD6 opens. This contributes to the activation of the third threshold block, which leads to the opening of both transistor switches. Both relays are switched on. Now winding III of transformer T1 is already connected to the load, but in antiphase with the mains voltage (“negative” voltage boost). In this case, the output will also have a voltage in the region of 205...225 volts.
When setting the control range, you need to carefully select zener diodes, since, as is known, they can differ significantly in the stabilization voltage spread.
Instead of KS218Zh (VD5), it is possible to use KS220Zh zener diodes. This zener diode must certainly have two anodes, since in the mains voltage range of 225...245 volts, when the zener diode VD6 opens, both transistors open, the circuit R3 - VD5 bypasses the resistance R6 of the threshold block R5-VD6-R6. To eliminate the shunting effect, the VD5 zener diode must have two anodes.
Zener diode VD5 for a voltage of no more than 20V. Zener diode VD1 - KS220Zh (22 V); it is possible to assemble a circuit of two zener diodes - D811 and D810. Zener diode KS222Zh (VD6) for 24 volts. It can be replaced with a circuit of zener diodes D813 and D810. Transistors from the series. Relays K1 and K2 - REN34, passport HP4.500.000-01.
The transformer is assembled on an OL50/80-25 magnetic core made of E360 (or E350) steel. The tape is 0.08 mm thick. Winding I - 2400 turns wound with PETV-2 0.355 wire (for rated voltage 220V). Windings II and III are equal, each containing 300 turns of PETV-2 0.9 wire (13.9 V).
It is necessary to adjust the stabilizer with a connected load in order to take into account the load on transformer T1.
Not everyone knows that the ideal operation of electrical networks is the ability to vary current and voltage, either less or more, by no more than ten percent. Of course, this percentage is calculated from standard 220 V. But, unfortunately, this is all only theoretical data. In real life, voltage surges can far exceed ten percent, and as a result, electrical appliances can lose their design capabilities and even break down.
In order to avoid such problems, you just need to purchase special equipment. Accordingly, the cost of such equipment will be high, and not every person will be able to afford it. This is why most people prefer to do it themselves. So, is it profitable to make voltage stabilizers with your own hands and what is required for this?
Voltage stabilizer and its features
In the modern world, not a single person can do without electrical appliances. And they, in turn, operate only from mains voltage. Unfortunately, all people experience short circuits, complete power outages, voltage surges, frequency deviations and that's not all. Many unpleasant situations can happen when working with electrical appliances. All this happens due to the fact that power lines wear out or the working resource has expired. Every year there are more and more “smart” devices that, due to voltage surges, not only have interruptions in their operation, but can burn out and no longer work at all. To prevent this from happening, you just need to make a 220V voltage stabilizer with your own hands and install it at home.
The most important criterion when choosing a stabilizer is power. There are many differences between these devices and only in power. For example, if you decide to purchase a stabilizer for a gas boiler, then a power of 0.5 kW will be quite enough. But if you choose it for a country house, then there are many more devices, so in this case you will need at least 9 kW, or even more.
Read also: Design features and principle of operation of the stabilizer
Stabilizer characteristics
Before asking the question of how to make a voltage stabilizer with your own hands, you need to thoroughly find out its characteristics.
The input voltage range is characterized by two thresholds – lower and upper. Operation between two thresholds is considered normal for the stabilizer. There are models with a large input voltage regulation scale, but you should not purchase them. Since the larger the parameter, the slower the device will respond.
Accuracy and speed of response also require special attention. All electrical appliances require power supply accuracy with a slight deviation of no more than five percent. Based on this, it is worth choosing a stabilizing device. But don’t forget about the speed of response. For example, if many different devices are connected to the stabilizer, then it should respond smoothly so that there are no strong jumps.
The power of the device is probably the easiest to choose. Since to do this you simply need to add up the voltage of all devices that operate in the room. This average number will determine how much power the stabilizer will need.
Phasing is distinguished between single-phase and three-phase. Which one to choose depends on how many phases the loads that are connected to the stabilizer have. If at least one device has three phases, this means the device must also be three-phase.
As for additional options and dimensions with weight, it all depends on the preferences of the buyer. Basically, they choose one with a minimum number of unnecessary functions, so that you can repair the voltage stabilizer yourself.
Types of devices and their features
Step stabilizers are safe and are used in rooms where there are industrial or household appliances. They can also provide complete protection for an apartment, private home and office.
The advantages of this equipment include small size, low price and reliability. The operating range of such a stabilizer is from 100 to 290 V.
Read also: How to choose the right generator
The disadvantages include low operation, in particular, this depends on how many energy drops there will be during the entire operating time. The relay contact group can easily burn out.
Electromechanical stabilizers operate automatically using an electric motor and gearbox. When servicing you don't need to do anything special. There is a smooth adjustment function, as well as an exact value of the output current. The quality of the device corresponds to the price.
Thyristor stabilizers have a long service life due to the use of semiconductor thyristors. They do not depend on the nature and intensity of changes. This device is considered the best of all, because the efficiency is approximately 98%. This means that there will be no glitches when turning on the devices. Thanks to this function, they are often used in production and at home. Unfortunately, the price of such a device is quite high.
Double conversion stabilizers have sensitive power, from approximately 1 to 30 kW. They are high quality, work without interruption and noise. The input current has a range from 118 to 300 V. The price is quite high, but this is due to the fact that the stabilizers are reliable and of high quality.
PWM stabilizers get their name due to pulse width modulation. This is one of the most modern models in the field of voltage stabilization. They do not have transformers. This makes it possible to significantly reduce size and weight. They also differ in high accuracy and instant response.
Stabilizer device
There are two main types of stabilizer - servo and triac.
The servo drive has an autotransformer, a servo drive stabilizer and a controller. This mechanism works thanks to an electric motor with graphite slider brushes. They are the ones who move the sliders along the winding of the autotransformer, which actually changes the output voltage.
A triac voltage stabilizer consists of a transformer with two windings, triac switches and a controller. Triac switches are connected to the second winding. This makes it possible to stabilize the voltage.
Operating principle
The essence of the stabilizer is to monitor changes in input voltage and the ability to adjust it based on the situation. When the voltage begins to change, the first phase is used to measure the voltage. After this, a reaction to change occurs. If the voltage change occurs within the permissible range, then it will try to level out to 220 V. If the voltage drops below the required level, the stabilizer begins to equalize the voltage to the maximum possible. If it is higher, then all devices are simply turned off for safety.
The article discusses the possibility of continuous switching of alternating current circuits using electromechanical relays. The possibility of reducing erosion of relay contacts and, as a result, increasing durability and reducing interference from operation has been shown using the example of a network voltage stabilizer for an apartment.
Idea
I came across an advertisement on the Internet on the website of Pribor LLC, Chelyabinsk:Selenium brand voltage stabilizers produced by our company are based on the principle of stepwise voltage regulation by continuously switching the autotransformer windings (patent for invention No. 2356082). Powerful, high-speed relays are used as keys.
Pictures of switching are shown (on the left is "Selenium", on the right - with the usual characteristics)
I was interested in this information, I remembered that in the cinema "Ukraine" there was also continuous voltage switching - there, during the switching period, a wirewound resistor was connected between adjacent contacts of the switch. I started looking on the Internet for anything useful about this. I was not able to get acquainted with invention No. 2356082.
I managed to find an article “Types of voltage stabilizers”, which talked about the possibility of connecting a diode to the relay contacts at the moment of switching. The idea is to switch the AC voltage during the positive half-cycle. In this case, you can connect a diode in parallel with the relay contacts for the switching period.
What does this method provide? Switching 220V changes to switching only 20V, and since there is no interruption of the load current, there is practically no arc. In addition, at low voltages, the arc practically does not occur. There is no arc - the contacts do not burn or wear out, reliability increases by 10 times or more. The durability of the contacts will be determined only by mechanical wear, which amounts to 10 million switching operations.
Based on this article, the most common relays were taken and the switch-off time, the time spent in the broken state and the switch-on time were measured. During the measurements, I saw contact bounce on the oscilloscope, which caused a lot of sparking and erosion of the contacts, which sharply reduces the service life of the relay.
To implement and test this idea, a 2 kW AC relay stabilizer was assembled to power the apartment. Auxiliary relays connect the diode only for the duration of the main relay switching during the positive half-cycle. It turned out that the relays have significant delay and bounce times, but, nevertheless, the switching operation was managed to fit into one half-cycle.
Schematic diagram
It consists of an autotransformer switched both at the input and output using a relay.
The circuit uses direct measurement of alternating voltage by a microcontroller. Output voltage via divider R13, R14, R15, R16 is supplied to the input of the microcontroller through a capacitor C10.
The relay and microcircuit are powered through a diode D3 and microcircuit U1. Button SB1 together with a resistor R1 serve to calibrate the stabilizer. Transistors Q1-Q4– amplifiers for relays.
Relays P1 and P2 are the main ones, and relays P1a and P2a, together with diodes D1 and D5, close the circuit when switching the main relays. To reduce the relay turn-off time in relay amplifiers, transistors are used BF422 and the relay windings are shunted by diodes 1N4007 and 150 Volt Zener diodes connected back to back.
To reduce impulse noise coming from the network, capacitors C1 and C11 are installed at the input and output of the stabilizer.
A three-color LED indicates voltage levels at the stabilizer input: red – low, green – normal, blue – high.
Program
The program is written in SI language (mikroC PRO for PIC), divided into blocks and provided with comments. The program uses direct measurement of alternating voltage by a microcontroller, which simplifies the circuit. Microprocessor applied PIC16F676.Program block zero waits for a falling zero crossing to appear
Based on this difference, either the alternating voltage value is measured, or the relay switches.
Program block izm_U measures the amplitudes of negative and positive half-cycles
In the main program, the measurement results are processed and, if necessary, a command is given to switch the relay.
For each relay group, separate turn-on and turn-off programs are written, taking into account the necessary delays R2on, R2off, R1on And R1off.
The 5th bit of port C is used in the program to send a clock pulse to the oscilloscope so that the results of the experiment can be viewed.
Specifications
When the input voltage changes within 195-245 Volts, the output voltage is maintained with an accuracy of 7%. When the input voltage changes within 185-255 Volts, the output voltage is maintained with an accuracy of 10%Output current in continuous mode 9 A.
Details and design
A transformer was used during assembly TPP 320-220-50 200 W. Its windings are connected at 240 Volts, which made it possible to reduce the no-load current. Main relays TIANBO HJQ-15F-1, and auxiliary LIMING JZC - 22F.All parts are installed on a printed circuit board mounted on the transformer. Diodes D1 and D5 must withstand a current of 30-50A during the switching time (5-10 ms).
The device is hung on the wall and covered with a tin casing
Settings
Setting up the device consists of checking continuous switching and setting the rated voltage to 220 Volts using the construction resistor R15 and the SB1 button.It is necessary to apply voltage from LATR to the input through an incandescent lamp with a power of 100 - 150 W, set the voltage to 220 Volts and hold the button to achieve a green glow by rotating the construction resistor.
After this, release the button, connect a voltmeter to the output of the device and, rotating the LATR, check the switching thresholds: lower 207 Volts and upper 232 Volts. In this case, the incandescent lamp should not flash or glow during switching, which indicates proper operation. Also, the operation of continuous switching can be seen on an oscilloscope; to do this, you need to connect an external trigger to the RC5 port and observe the output voltage of the stabilizer by changing the input voltage. During switching moments, the sine wave at the output should not be interrupted.
When the output voltage is less than 187V, the red diode lights up and the green diode blinks.
When the output voltage is greater than 242V, the blue diode lights up and the green diode blinks.
The stabilizer has been working for me for the 3rd month and has shown itself to be very good. Before this, a stabilizer of a previous design worked for me. It worked well, but sometimes the computer's uninterruptible power supply would trip when it switched. With the new stabilizer, this problem disappeared forever.
Considering that contact erosion in the relay has sharply decreased (there is practically no sparking), it would be possible to use less powerful relays as the main ones (LIMING JZC - 22F).
Noticed shortcomings
It was quite difficult to select the relay delay time in the program.For such switching, it is advisable to use faster-acting relays.
conclusions
a) Continuous switching of alternating current circuits using relays is a very real and solvable problem.b) You can use a thyristor or triac as an auxiliary relay, then there will be no voltage drop across the relay, and the triac will not have time to heat up in 10 ms.
c) In this mode, contact sparking is sharply reduced, durability increases, and interference from relay switching is reduced
Sources used
1. on the website “Energy Saving in Ukraine”2. Official website of the enterprise LLC "Pribor", Chelyabinsk
3. Datasheets for details
Files
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