UPS for a computer: what you should pay attention to when purchasing. Uninterruptible power supply systems: types, characteristics, installation. Uninterruptible power supplies

Making a powerful source uninterruptible power supply based on a standard UPS, connecting two KAMAZ batteries to it. We also do automatic ventilation when switching to autonomous mode.

This is the reality that Russian power grids force consumers themselves to care about the stability of the electricity they receive. In our case, it is necessary to solve two important problems: a large voltage drop (typical of the hot/cold season, when air conditioners/electric heaters are turned on) and a complete power outage (“knockout” of machines, accidents at a substation, etc.).

If the first problem is easily solved by installing an autotransformer, which allows you to obtain a stable voltage of 220 volts at the output, then the second requires the organization of an uninterruptible power supply system designed for a long period of autonomous operation.

You can organize uninterrupted supply of a country house or garage by upgrading computer systems. After two years of operation, the internal batteries in any UPS degrade. Uninterruptible power supplies with non-working batteries have been repeatedly observed on the radio market at a symbolic price of 1000 rubles.

For long battery life, an uninterruptible power supply must be connected to batteries large capacity. The best option would be starter batteries from KAMAZ vehicles - 140 Ah. Since most powerful uninterruptible power supplies use batteries with a total voltage of 24 volts, we need a pair of batteries connected in series. The duration of the autonomous power supply will depend on the condition of your batteries.

First of all, we take out and throw away the faulty battery. For ease of connection external battery For a large capacity, we need to make contact clamps (preferably red and black, indicating plus and minus, respectively). To do this, we make two holes on the front panel of the uninterruptible power supply, fix the contact clips and solder the wires to them that went to the internal battery.

Long-term operation in the state of converting battery energy into a voltage of 220 volts is accompanied by large heating. To prevent premature failure, it was decided to install two conventional fans measuring 80x80x25 mm on the ventilation grille.

The fans are connected in series. To start the fans in conversion mode, we use an LED, which indicates the operation of the uninterruptible battery power supply. We solder the leads of the LED to the windings of a small relay with wires. We solder a wire from the incoming positive of our battery to one of the relay contacts. The second is a free red fan wire. We solder the free black wire of the fan to the incoming negative of the battery.

All! Now, when the uninterruptible power supply switches to battery mode, the cooling will automatically turn on.

An uninterruptible power supply (UPS), or also called UPS (uninterruptible power supply), is, in fact, charger, battery and boost converter in one package. A simple uninterruptible power supply for a computer with a power from 300 W to 500 W costs 2000 - 3500 rubles. Unfortunately, the battery built into them usually has a capacity of 7 to 8 Ah. This will be enough to power the computer for 4 minutes. In more expensive models, a rechargeable battery of up to 15–20 A is installed; this capacity can be enough for 10–30 minutes of uninterrupted power supply to the computer.

Backup scheme for constructing a UPS (Off– line, Standby)

Most often UPS used for power supply personal computers, built according to the Off-Line backup scheme. Almost all low-cost UPSs, ranging from 300 W to 720 W, sold on domestic market, are arranged according to this scheme.

The backup scheme for constructing a UPS (Off-line, Standby) is carried out as follows:

1. With a stable voltage in the network (in normal mode) the connected load is powered from the primary electrical network.
2. When the voltage in the network decreases or fails, the load is connected to power through a step-up inverter converter from the built-in battery.
3. When the mains voltage is restored, the load is switched back to mains power.

Each time the power is switched, a voltage surge occurs, which is unacceptable for powering servers and databases, but for personal computers this is not critical.

Implement the scheme yourself Off-line You can use a relay with a coil for 220V alternating voltage.

1. When the network voltage is 220V, it’s normal closed contacts This relay will keep the boost converter disabled.
2. When in the network will disappear voltage is 220V, the relay releases the contacts and connects the battery together with the converter to the computer power supply.
3. When the 220V voltage is restored, the relay turns on again and switches the computer to mains power.

You also definitely need to organize a charging circuit for the battery of your homemade uninterruptible power supply.

Homemade charger for UPS battery. Double conversion UPS design diagram (Online) How to install a chandelier in your home yourself

UPS are used for protection various types electrical equipment first computer equipment from voltage surges in the network, and can also maintain their operation for several minutes, hours or even days during a complete power outage

An uninterruptible power supply can cope with the following electrical problems: complete shutdown of the power supply network, high-voltage impulse noise, long-term and short-term voltage surges; high-frequency noise or interference occurring in the electrical network, frequency deviation of more than 3 Hz.

Important parameters of the UPS are the time it takes to switch the load to power from the batteries and the battery life.

Backup UPS design in operating mode, the load is powered from the electrical network, which the uninterruptible power supply filters for high-voltage pulses and electromagnetic interference passive filters.

If the mains voltage deviates beyond the normalized values, the load is automatically connected to battery power using an inverter circuit, which is included in each UPS. As soon as the voltage is the network will enter Normally, the uninterruptible power supply will switch the load to mains power.

Interactive UPS diagram similar to the backup circuit, but additionally a step voltage stabilizer based on an autotransformer is installed at the input, which allows you to regulate the output voltage. During normal operation, UPSs operating according to an interactive scheme do not regulate the frequency, but in the absence of voltage, it begins to be powered by an inverter with a battery. The advantage of this scheme is more short time switching In addition, the inverter is synchronized with the input voltage.

Double conversion UPS circuit works as follows: The input AC voltage is converted to DC, then back to AC using an inverter. In the absence of input voltage, switching the load to battery power occurs instantly, since the batteries are constantly connected to the circuit.

Main blocks and components that may be included in the UPS:

Switching device
Surge filter
Charger
Battery
Inverter: AC-DC converter, Stabilizer DC voltage, DC to AC converter
Bypass switching device
Current sensor
Source filter
Temperature sensor
Interface
Display device

Input mains voltage 220V, 50Hz is supplied through a switching device and a surge filter to the charger. A surge protector is necessary to prevent interference from entering the mains supply; the charger charges the battery provided that mains voltage is available.

The inverter is included in any UPS. It is built on the basis of a semiconductor converter of direct voltage from the battery into alternating voltage supplied to the load. Often an inverter combines the functions of both the inverter itself and the charger. Depending on the type of UPS, the inverter produces voltage of different shapes

Bypass is a switching device. This device is used to directly connect the input and output of the UPS, eliminating the power redundancy circuit.

The bypass performs the following functions:

turning on or off the UPS

transferring the load from the inverter to bypass in case of overloads and short circuits at the output

transferring the load from the inverter to bypass in order to reduce electricity losses

The static bypass is assembled on the basis of a thyristor switch from back-to-back thyristors connected in parallel. The key is controlled by the UPS control system

The switching power supply was taken ready-made for 28 V, 50A, but you can assemble it yourself and there are a great many circuits. TO pulse source the power supply is connected to two series-connected 12 volt car battery. The inverter was also used ready-made, since the price of its components is almost twice as high as the finished device. This UPS is enough for almost a day of energy consumption in a small private house. In case of a long outage, and in our Siberian expanses this often happens, I turn on the diesel generator for 6 hours.

Our UPS is designed for the following capabilities: direct conversion from 12 V DC to 220 V AC with a frequency of 50 Hz. The maximum power of this UPS circuit is 220 W. The reverse conversion is used to charge the battery. Charge current 6 A. The circuit provides fast switching from direct conversion to reverse mode.

A clock generator is made on the radio components VT3, VT4, R3...R6, C5, C6, generating pulses with a repetition rate of 50 Hz. Generator, sets the operating mode bipolar transistors VT1, VT6. Windings IIa, IIb of the transformer are connected to their collector circuit. The network filter is assembled on passive components C1, C2, L1, and the clock generator filter is based on radio elements VD1, SZ, C4.

Uninterruptible power supply

In many regions today, planned and unscheduled power outages are often practiced for quite some time. long term. As a result, people who are accustomed to information abundance find themselves for some time in a kind of vacuum, when not only there is no lighting, but also the TV, radio, and computer do not work. In such cases, it is very useful to have an alternative source of energy. It can be a rechargeable battery if you equip it with a DC-to-AC voltage converter (inverter) and automation that monitors the health of the network, the state of charge of the battery, and also promptly switches the load to power from the network or battery and controls the recharging of the latter.

Currently, imported uninterruptible power supplies (UPS, in English UPS) produced by various companies are available for sale. Typically, they are designed to prevent computer crashes and loss of valuable data stored on them in conditions of unreliable power supply. However, such UPSs are designed to power active or active-capacitive loads, and their battery capacity is enough for only a few minutes of computer operation. The design and design of affordable imported UPSs are such that they are almost impossible to adapt, for example, to power a TV for several hours.

You can make a UPS with the necessary parameters yourself. Such a device must provide uninterrupted power supply to a load of up to 300 W. This is enough to “pull” any TV, from portable to “mastodon” ULPTST. As a backup source, it is advisable to use a car battery with a capacity of 55...60 Ah, which is not difficult to purchase. Those who own a passenger car already have such a battery.

The time of continuous power supply to the load from the battery can be easily calculated using the formula: T=kQU/P, where T is time continuous operation, h; k=0.8...0.9 - inverter efficiency; Q—battery capacity, Ah; U—battery voltage, V; P – load power W.

With the above initial data, it will be a little more than two hours, and with a load of lower power it will increase accordingly. For example, a computer with a standard configuration Pentium processor The 166MMX will be able to run on battery power for almost six hours.

It is desirable that the UPS output voltage waveform remains sinusoidal in any operating mode. But to achieve this, it would be necessary to significantly increase the mass and cost of the device. Practice has shown that ordinary household electrical appliances operate normally even when powered by pulsed voltage rectangular shape, the formation costs of which are significantly lower. In case of emergency, you can connect the load to the UPS through a ferroresonant stabilizer, which, by passing the first harmonic impulse voltage, will suppress all others. To protect the battery and UPS elements from overloads, especially in starting modes, you need both fast-acting electronic current protection and more inertial protection using a fuse link.

Designed taking into account the above, the proposed UPS operates as a step regulator at a mains voltage of 165...242 V, maintaining an output voltage of 220 V +10%. Unlike imported devices, most of which react only to a decrease in voltage, it automatically switches to power supply mode from the battery when the network voltage goes beyond the specified limits in any direction. The switching process takes no more than 20 ms, after which a pulse voltage with a frequency of 50 Hz appears at the output of the UPS, the effective value of which is maintained at 220 V + 10% until normal voltage is restored in the network or the battery is discharged to 10.8 V. In the latter In this case, the power supply to the load is stopped, since further discharge is dangerous for the battery. Automatic return to step control mode occurs approximately a second after recovery normal voltage online.

The UPS diagram is shown in Fig. 1. During its development, it was decided to use the same transformer T2 in all operating modes. This required the use of additional switching circuits and a more complex control device, but significantly improved the weight and size characteristics of the UPS and reduced its cost.

Node A1, through the step-down and decoupling transformer T1, constantly monitors the voltage in the electrical network to which the XP1 plug is connected. Depending on the voltage value, the node generates a signal NETWORK OK and commands to turn on relays K1 and K2.

Then, through an electronic switch - a diode bridge VD7-VD10 with an optothyristor U1 in the diagonal - the mains voltage is supplied to the series-connected windings IV and V or only to winding IV of transformer T2 (depending on the position of the contacts of relay K2). Node A6 monitors, by the voltage drop across resistor R12, shunted by diode VD11, the current flowing through the optothyristor U1, and in its absence, generates a NO CURRENT signal, necessary for the operation of the UPS automation. The output socket XS1, to which the load is connected, receives voltage from windings IV and V of transformer T2.

The degree of charge of the battery GB1 based on its voltage is controlled by node A3. Having detected that the voltage is below 12.9 V, if the network is working properly, it issues the CHARGE command and cancels it after the voltage has increased to 14.3 V as a result of recharging. If the network is faulty and the load is powered by the battery, node A3 does not allows excessive discharge of the latter and, at a voltage of less than 10.8 V, breaks the circuit of the relay winding K, transferring the UPS to standby mode.

The inverter consists of a powerful push-pull output stage based on field-effect transistors VT3-VT9 and driver A5 that generates pulses supplied to their gates. The drain circuits of each group of transistors include halves of windings I and III of transformer T2 connected in series. Its winding II, diode bridge VD12-VD15 and transistor VT9 are designed to form pauses between output voltage pulses. At the rated voltage of battery GB1 (12.6 V), the pause duration is approximately half the pulse duration, which corresponds to the minimum of the third harmonic in the inverter output voltage spectrum. The effective value of such a voltage is 1.23 times less than the amplitude (for a sinusoid this ratio is 1.41).

Depending on the state of charge of the GB1 battery, its voltage and the output voltage amplitude proportional to it change by 30%, however, the effective value of the latter due to pulse width modulation (PWM) is maintained almost unchanged, which has a beneficial effect on the operation of lighting and electric heating devices, including filaments vacuum tubes and picture tubes. Practice has shown that changes in the amplitude of the supply voltage over a wide range have virtually no effect on the operation of televisions and computers, the power supplies of which are, as a rule, equipped with voltage stabilizers.

Oxide capacitors are characterized by increased losses due to the fact that one of the plates is an electrolyte with a relatively large active volume resistance. Therefore, when repeating the design with capacitors different from those recommended, it is necessary to take into account the recommendations set out in and the characteristics of the capacitors of the type used.

In addition to diodes VD16, VD17, the rectifier bridge of the charger includes optothyristors U2, U3, so it works when current flows through the emitting diodes of the latter, and is turned off otherwise. The control circuits for the charger and other UPS components are located in the automation unit A4.

If the device is connected to the network and the voltage in it is within 165...242 V, after closing the contacts of switch SA2 "On." node A1 will give a command to turn on relay K1, the closed contacts of which will turn on the UPS and the latter will switch to step voltage regulator mode. Button SB1 "Start" is used to start the UPS in the absence of normal voltage in the network. After pressing this button, all UPS components are supplied with supply voltage directly from the battery GB1 or through the stabilizer A2. If the battery voltage is higher than 12.2 V, node A3 will turn on relay K1 through the closed contacts of switch SA1. Now the SB1 button can be released. By turning off SA1, you can prevent the UPS from operating when the network is faulty. This is what they do if backup power there is no need, for example, when all loads are turned off, and the UPS itself remains connected to the network, periodically recharging the battery.

When the network is working properly, current flows through the emitting diode of the optothyristor U1 and voltage is supplied to the XS1 socket. The operation of the inverter is blocked by the low level of the ENABLE signal generated in the automation unit A4. If the network voltage is below 195 V, the signal from node A1 triggers relay K2 and transformer T2 turns into an autotransformer, increasing the voltage at the load by 1.2 times. As a result, it remains equal to 220 V +10%.

After the voltage in the network goes beyond the permissible limits, you cannot turn on the UPS inverter without waiting for the thyristor U1 to close, which will not occur before the current drops to almost zero, due to the energy accumulated in the inductances of transformer 2 and the load. This circumstance makes the usual synchronization of the inverter master oscillator with the network voltage impossible and forces one to select the moment of changing the UPS operating mode, taking into account the residual induction in the magnetic circuit of transformer T2 (the magnetic circuits of the inductive load elements are in similar conditions).

The organization of the switching process will be described in detail in the section devoted to the operation of the A4 automation unit.

The network voltage monitoring unit (A1) is assembled according to the diagram shown in Fig. 2. A voltage proportional to the mains voltage is supplied from winding II of transformer T (see Fig. 1) to the rectifier bridge VD19 and then, turning into a pulsating voltage, to three identical comparators assembled on CMOS chips DD1-DD3. The result of processing the output signals of the comparators on the DD1 and DD2 microcircuits is the logical level at the output of parallel-connected elements DD2.5, DD2.6. High indicates that the mains voltage is within the range of 165...242 V, low indicates that it has gone beyond them. In the latter case, capacitor C24 quickly discharges through diode VD29 and the logical level at the output of the Schmitt trigger from elements DD4.1-DD4.3 becomes low, informing all UPS nodes that the NETWORK OK condition is not satisfied.

After normal voltage and a high logical level are restored in the network at the outputs of elements DD2.5, DD2.6, diode VD29 closes, capacitor C24 begins to slowly charge through resistor R42. As a result, with a delay of approximately 1 s, the high level of the NETWORK OK signal will be set. The delay is necessary so that power to the UPS load from the battery stops only after possible transients in the network have ended. The output signal of elements DD2.5, DD2.6 also controls relay K1 (see Fig. 1) through a switch on transistor VT10.

In order not to discharge the battery in standby mode, the DD1 and DD2 microcircuits of node A1 are powered directly from the network through transformer T1, diode bridge VD19, diode VD18 and a stabilizer based on elements R19, VD20.

The response threshold of the comparator on the DD3 chip corresponds to a network voltage of 195 V. If it is less, the DD5.1 ​​element closes the power circuit of the K2 relay winding and it switches the windings of the T2 transformer (see Fig. 1). To ensure that this only happens when the network is working, one of the inputs of element DD5.1 ​​is supplied with the NETWORK OK signal from the outputs of elements DD4.2, DD4.3.

When talking about network voltage, we usually mean its effective (rms) value, the direct measurement of which is difficult. The shape of the alternating voltage in the network is quite close to sinusoidal (the harmonic coefficient usually does not exceed 6%), its amplitude Um and the effective value Ueff are related by the relation Ueff = 0.707 Um. Therefore, it is enough to monitor the amplitude. The difficulty is that the sinusoid reaches its amplitude value for a short time, and the output signal of the comparator must be continuous.

Since all three comparators are identical, we will analyze the operation of one of them - on the DD1 chip. As soon as the instantaneous voltage value exceeds the triggering threshold of the Schmitt trigger on elements DD1.1, DD1.2, it will discharge capacitor C20 through diode VD24, which will trigger the second Schmitt trigger on elements DD1.3 and DD1.4. However, after reducing the instantaneous voltage value to a value less than the release threshold of the first trigger, the second will remain triggered until capacitor C20 is charged through resistor R32.

The values ​​of these elements are chosen in such a way that the release delay of the second trigger is slightly more than 10 ms - half the period of the mains voltage. Therefore, while the amplitude of the controlled voltage is above the threshold, the discharge of capacitor C20 is repeated in each half-cycle and the voltage on it does not have time to reach the release threshold of the second trigger. The output of element DD1.4 remains at a constant high level. It will change to low if the amplitude of the input voltage has decreased and capacitor C20 has managed to charge in the next half-cycle.

Characteristics digital chips the K561 series, on which the comparators are assembled, are quite stable. In the temperature range of +15...35 "C, typical of residential premises, the set thresholds change by no more than 0.6%, which is quite enough for a UPS.

The +5 V voltage stabilizer (A2) is designed to power all digital UPS microcircuits, with the exception of DD1 and DD2. Its diagram is shown in Fig. 3. Integrated stabilizer DA1 is included according to the standard circuit. Capacitors C27-C44 are blocking. They are installed in close proximity to the power pins of each microcircuit.

Battery voltage control unit (A3). The node diagram is shown in Fig. 4. Timers K1006VI1 (DA2 DA3) are used as comparators. Resistors R50-R58 set their response and release thresholds. Capacitors C45 and C47 are used to suppress impulse noise. While the battery voltage is above 10.8 V, the internal transistor of the DA2 chip is open, the collector of which is connected to pin 7. As soon as it becomes less than specified, the transistor will close and reopen only after the battery voltage increases to 12.2 V.

The operation of a similar comparator on the DA3 chip is allowed only when the level of the RS signal received at its input is high: THE NETWORK IS OK. The comparator output turns the battery charger on and off. The actuation and release thresholds are 12.9 and 14.3 V, respectively.

Automation unit (A4). In order for the UPS inverter to turn on in the correct phase after a power outage, it is necessary to know the direction of the residual induction in the magnetic circuit of transformer T2. As is known, the voltage on the winding of a transformer is proportional to the rate of change of magnetic induction in its magnetic circuit. Therefore, it can be measured indirectly by integrating the voltage. This operation is performed by the integrating circuit R59C49C50C51 (Fig. 5). Diodes VD31, VD32 protect oxide capacitors C50, C51 from voltage of incorrect polarity.

When the voltage proportional to the induction at the output of the integrating circuit is positive, transistor VT11 is open, trigger DD6.1 is set to the state corresponding to the log. 1 at its pin 5. Otherwise, transistors VT12 and VT13 will be open, and the trigger state will be the opposite. Thus, the logical level at the output of the trigger is uniquely related to the direction of the magnetic flux in the magnetic circuit of transformer T2. After the network is turned off, the DD6.1 trigger remains in a state corresponding to residual induction.

The switch on transistor VT14 forms square pulses from the mains voltage supplied to its input from the secondary winding of transformer T1 (see Fig. 1). Element DD7.1 compares their phase with the induction phase. If there is a coincidence, the high logical level at its output and the same one - the NETWORK OK signal, set the DD6.2 mode trigger through the DD8.1 element to a state corresponding to the operation of the UPS from the network. As a result low level The ENABLE signal prohibits the operation of the inverter. At the same time, logic elements DD8.3, DD11.1, DD12.1 and DD12.2 generate signals that turn on the optothyristor U1 of the electronic switch, and at a high level of the CHARGE signal, also the optothyristor U2 and U3 (see Fig. 1).
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Log. 1 at the output of element DD7.2 appears when the phases of induction and oscillations of the inverter master oscillator coincide. However, this is not enough to switch the DD6.2 trigger and switch the UPS to battery mode. The logical node, which includes diodes VD33 and VD34 with resistor R67, elements DD4.4—DD4.6, DD8.2, ensures that switching occurs only when the NETWORK signal level is low, when the signal is high - NO CURRENT and always at the moment of output master generator of the inverter of the next pulse.

When the MODE signal level changes, pulses are generated at the output of the DD7.3 element, allowing the generator to operate on the elements of the DD9 microcircuit for approximately 1 s. As a result, the BQ1 piezo emitter produces sound signals indicating a change in the UPS operating mode, and in the event of a power outage, the signal sounds a little longer than when it is restored.

The inverter driver (A5) is built according to the circuit shown in Fig. 6. DA4 chip - master oscillator. Its connection circuit is typical for the K1006VI1 timer; it is described in detail in. When the MODE signal level is low, the repetition rate of the generated pulses is 100 Hz. Otherwise, in parallel with the timing resistors R76 and R77 of the generator, a relatively low-resistance resistor R75 is connected through an open diode VD35 and the frequency is increased to approximately 2500 Hz. Consequently, the oscillation phase of the master generator, required at the moment the UPS switches to powering the load from the battery, will occur faster.

As already mentioned, the effective value of the inverter output voltage is stabilized using PWM. The battery voltage, through the VD38 zener diode and the R84C56 filter, powers the timing circuit of the one-shot unit assembled on the DA5 chip. As a result, the duration of the pulses generated by it in response to each pulse of the master oscillator decreases with increasing this voltage. The bias created by the Zener diode VD38 brings this dependence closer to that required for stabilization effective value output voltage, and resistor R82 increases the current flowing through the zener diode to the required value.

Trigger DD13.2 divides the pulse frequency of the master oscillator by two. As a result, one-shot pulses pass through logic elements DD10.3, DD10.4. DD11.3, DD11.4 and switches on transistors VT19, VT20 with a frequency of 50 Hz alternately enter the gates of power transistors VT3-VT5 and VT6-VT8 (see Fig. 1) and open them. During pauses between pulses, transistor VT9 is open, the signal to its gate is supplied through elements DD8.4 and DD11.2 and transistor switch VT18. The inverter operation may be blocked by a low ENABLE signal. In this state, there are no unlocking pulses on the gates of all power transistors.

The current protection unit for power transistors consists of diodes VD36, VD37, resistors R79—R81, R83, transistor VT17 and trigger DD13.1. At normal operation inverter transistor VT17 is closed. Trigger DD13.1, thanks to the master oscillator pulses arriving at its input S, is in a state corresponding to high level on the way out. The voltage at the point of connection of the anodes of diodes VD36 and VD37 is linearly related to the lower voltage at the drains of the transistors to which their cathodes are connected (the diode connected to those drains where the voltage is higher is closed).

Lower voltage - always on open drains at the moment transistors and proportional to the current flowing in their channels. The values ​​of resistors R79-R81 are selected in such a way that when the current increases to 120 A, the voltage at the base of transistor VT17 reaches its opening threshold. As a result, a low logic level from the collector of the opened transistor will go to the R input of the DD13.1 trigger and switch it. The levels at the outputs of the trigger and element DD10.2 will become low. This will interrupt the opening pulse on the gates of the power transistors, which will lead to their protective shutdown.

All transistors will remain closed only until the next pulse of the master oscillator, which will arrive at the S input of the DD13.1 trigger at the beginning of the next half-cycle. The pulse duration is 200 μs, and all this time the level at pin 5 of the trigger will be high regardless of the state of input R. The short-term blocking of current protection achieved in this way allows the UPS to operate stably on capacitive loads (for example, transformerless power supplies electronic equipment), but excludes damage caused by short circuit loads.

Current control unit (A6), the diagram of which is shown in Fig. 7, maintains a low level of the NO CURRENT signal at its output until the instantaneous value of the current flowing through the electronic switch decreases to a value sufficient to close the optothyristor U1 (see Fig. 1). The sensor is resistor R11, connected in series with U1. Diode VD11 is necessary to limit the excessive voltage drop across the resistor at operating current values. Optocoupler U4 isolates the output circuit of the node from the rest of its circuits that are under mains voltage. While current flows through resistor R11, transistor VT21 and phototransistor of optocoupler U4 will be open, the emitting diode of which is connected to the collector circuit of transistor VT21.

To power the unit, a specially designed winding VI of transformer T2 is used, the voltage of which rectifies the diode bridge VD40 and stabilizes the circuit R99VD41. The main function of capacitor C59 is to smooth out the ripples of the rectified voltage. However, the energy stored in it is enough to power the current control unit when changing the UPS mode, when there is no longer any voltage in the network and the inverter is not yet working.

Details and design. Most parts, except for power and large ones, are located on a common printed circuit board without division into functional units. Switches SA1, SA2, button SB1, LEDs HL1-HL4, socket XS1 are located on the front, and terminals for connecting the battery GB1 and fuse holders FU1, FU2 are on the rear or side panels of the UPS.

The fuel elements are installed on six heat sinks made of aluminum sheet with a thickness of at least 3 mm. Listed below are the parts found on each of them, in parentheses are the dimensions of the heat sink in millimeters: VT3—VT5 (150x50); VT6—VT8 (150x50); VT9, VD12—VD15 (150x50); U2, VD16 (150x80); U3. VD17 (150x80); DA1 (30x30).

Instead of the IRFZ44 transistors indicated in the diagram, KP723A or other MOSFET structures with a maximum drain current induced by the p channel of at least 40 A, a maximum drain-to-source voltage of at least 55 V and an open channel resistance of no more than 0.025 Ohms are suitable as VT3-VT9. The remaining transistors can be replaced with any low-power bipolar transistors of the appropriate structure.

Capacitors C2, C4—C6 are K73-17 film capacitors, the rest (with the exception of oxide ones) are any ceramic ones, for example, KM-5, KM-6 or K10-17. Oxide capacitors - K50-ZB, K50-6, K50-16. Capacitors C7-C14 require special attention. Flows through them AC approximately 5.5 A. Calculation shows that in this case the internal temperature of the K50-6 capacitors, having those indicated in Fig. 1 operating voltage and capacity will remain within acceptable limits at an ambient temperature of no more than 50 C, which is quite acceptable for a device used in a residential area. If such capacitors are not found, you should install them instead larger number capacitors of smaller capacity, keeping the total unchanged. Reduce the number of parallel-connected capacitors by increasing the capacitance of each in this case unacceptable. Capacitors designed for a constant voltage of less than 50 V cannot be used.

Transformer T1 has special requirements. Its primary winding, constantly connected to the network, must long time withstand increased voltage up to 380 V. For this reason, the UPS manufactured by the author uses a 380/26 V transformer from a device designed to monitor the presence three-phase voltage. If you can’t find something like this, you should take two identical low-power 220/9 V transformers (for example, from network power supplies for radios or video game consoles) and connect their primary and secondary windings in series. The difference in the transformation ratio is easily taken into account when setting up the comparators of node A1. Data for self-production of transformer T1: magnetic core - Ш12x16, winding I - 6910 turns of PEV-2 0.06 wire. winding II - 473 turns of wire PEV-2 0.21..

The magnetic core of transformer T2 is tape ШЛ32х50. The windings are wound in ascending order of the numbers indicated in the diagram (see Fig. 1). Windings I and III each contain 24 turns of a copper busbar with a cross-section of 10 mm. Winding II - 44 turns of PEV-2 1.62 wire, IV - 446 turns of PEV-2 0.9 wire, V - 90 turns of PEV-2 0.9 wire, VI - 44 turns of PEV-2 0.38 wire. Each wound layer is compacted using a mallet and a stop, then impregnated with insulating varnish (in extreme cases, BF glue). Between windings III and IV, as well as V and VI, insulating gaskets must be made. The finished coil is dried in a heating cabinet using a technology corresponding to the impregnating material used.

Choke L1 is wound with PEV-2 0.72 wire until the cavity of the B-36 armored magnetic core made of 2000NM ferrite is filled. During assembly, a 0.5 mm thick gasket made of non-magnetic material (for example, paper) is inserted between the ferrite cups.

Relay K1 - RES15 passport RS4.591.004 or similar for 12 V, K2 - imported JZC-20F (4088) 10ADC12V with a winding resistance of 400 Ohms. Instead, relays RP21, RPU-2 with an operating voltage of 12 V and contacts designed for switching alternating current up to 10 A at a voltage of 220 V are suitable. BQ1 is a piezoceramic sound emitter of any type. As a fuse link RJ1, you can use a piece of copper wire with a diameter of 0.72 and a length of 15...20 mm.

Setting up a UPS. To carry it out, you need adjustable DC (0...15 V, 1 A) and alternating (0...250 V, 1 A, 50 Hz) voltage sources, an oscilloscope, a 10 A DC ammeter, DC voltmeters (0. ..15 V) and alternating (0...300V) voltage. When working with alternating current high voltage precautions should be taken.

The AC voltmeter should be electromagnetic system, for example, panel board E377. Instruments of other systems, including conventional avometers, when measuring the pulse voltage generated by the inverter, give readings that are completely inconsistent with reality.

Setup begins after assembling and checking the installation of the UPS, without connecting transformer T2 and battery GB1 to it. Instead of transformer windings, resistors with a power of at least 1 W (for example, MLT-1) and a resistance of 470... 1000 Ohms are temporarily connected between the drains of transistors VT3-VT5, VT6-VT8 and the +12 V circuit. A similar resistor is installed between this circuit and the drain of transistor VT9. To it, bypassing the contacts of switch SA1 and relay K1, they connect regulated source constant voltage.

First of all, check the +5 V voltage regulator (DA1). It should remain practically unchanged when adjusting the source voltage within 10...15 V. Then, by connecting the oscilloscope to pin 3 of the DA2 chip, using resistor R50, ensure that at a voltage below 10.8 V, the low logic level here is replaced by a high one. After this, set the voltage to 12.6 V in the +12 V circuit and connect the alternating voltage source to winding I of transformer T1, having previously disconnected it from all other circuits. By adjusting the alternating voltage within 160...250 V, make sure that the voltage on the zener diode VD20 remains constant, which should remain approximately 5.6 V.

By connecting the oscilloscope to pin 8 of the DD1 chip, using resistor R15, ensure that the low level changes to high when the alternating voltage exceeds 242 V. You may need to select the value of resistor R17 for this. Switching should be clear, without “bouncing”, otherwise install resistor R31 of a slightly larger value. The comparators on the DD2 and DD3 microcircuits are adjusted in a similar way, ensuring that they operate at voltages of 165 and 195 V, respectively. Together with the comparator on the DD3 chip, relay K2 should operate.

Next, set the AC source voltage to 220 V and connect the oscilloscope to pin 3 of the DA3 chip. By rotating the axis of the trimming resistor R55, they ensure that when the voltage in the +12 V circuit increases above 14.3 V, the high logical level at this pin changes to a low one. At the same time, the HL4 LED should go out. When the voltage on the primary winding of transformer T1 is more than 242 or less than 165 V, the HL2 LED should light up, signaling that the UPS is in power supply mode to the load from the battery.

By connecting an oscilloscope to pin 3 of the DA2 chip, make sure that there are pulses with a repetition rate of approximately 2500 Hz. Having again set the alternating voltage to the nominal voltage (220 V), make sure that the HL2 LED has gone out and the oscillation frequency of the DA2 multivibrator has decreased to 100 Hz. It can be set accurately by synchronizing the sweep of the oscilloscope with the network and using the trimming resistor R76 to ensure that the waveform of the pulses on the screen is stationary.

Voltage oscillograms at the drains of transistors VT3-VT9 should correspond to those shown in Fig. 8. The operation of the current protection is checked by removing diodes VD36 and VD37. After this, the negative pulses on the drains of transistors VT3-VT5 and VT6-VT8 should become very narrow. At the end of the test, do not forget to replace the diodes.

It is recommended to turn on the UPS for the first time by connecting the battery to it via an ammeter and installing a fuse-link with an operating current of 5... 10 A as FU1. Without inserting the XP1 plug into the power outlet, set switch SA2 to the "On" position. and press the SB1 “Start” button. The HL3 "On" LEDs should light up. and HL2 "Battery". The fact that the UPS inverter has started working can be determined by the characteristic sound produced by transformer T2. The battery discharge current without load should not exceed 0.4 A.

By connecting a voltmeter to the XS1 socket, using a trimming resistor R86, make sure it shows 220 V. More precisely, the rated output voltage of the inverter can be set using an incandescent lamp with a power of 50... 150 W. Alternately connecting it to the XS1 socket and to the output of an adjustable autotransformer with a voltage of 220 V, set the axis of the resistor R86 to a position in which the brightness of the lamp is the same in both cases.

Then insert the XP1 plug into the power outlet. A second after this, the inverter should automatically turn off, and the UPS should switch to stepwise regulation mode of the mains voltage. When changing the mode, the HL2 “Battery” LED goes out, the HL1 “Network” LED lights up and a beep sounds. beep. If the battery voltage is less than 12.9 V, the HL4 “Charging” LED should light up and the ammeter should show a charging current of 4...6 A.

If the battery voltage is higher than specified, the charger will not turn on. To check it, the battery will have to be partially discharged by connecting a load of at least 50 W to the XS1 socket, disconnecting the XP1 plug from the network and letting the UPS operate in this mode until the battery voltage drops to 12 V. After that, reinserting the XP1 plug into the socket, make sure that the battery has started to charge. When its voltage rises to 14.3 V, charging will automatically stop. Having completed all the checks, install fuse link FU1 with a current of 50 A in the UPS and begin its full operation.

LITERATURE
1. Evseev A. Automatic charger for batteries: Collection: “To help the radio amateur”, vol. 83, p. 12-17. - M.: DOSAAF. 1983.
2. Nyvelt G. Power sources radio-electronic equipment. - M.: Radio and Communications, 1986.
3. Anufriev Yu Gusev V., Smirnov V. Operational characteristics and reliability electrical capacitors. - M.: Energy, 1976.
4. Zeldin E. Digital integrated circuits in information and measuring equipment. - L.: Energoatomizda, 1986.
5. Traister R. Amateur radio circuits based on IC type 555. - M.: Mir. 1988.
6. Microcircuits for household radio equipment. Directory. - M.: Radio and Communications, 1989.
V. VOLODIN, Odessa, Ukraine
Radio 5-6 2001

For many industries and household appliances constant voltage is required. We propose to consider what an industrial uninterruptible power supply for a boiler and computer is, the connection diagram of the device, as well as the operating principle of the UPS.

Useful information about uninterruptible power supply

Uninterruptible power supply OKVED 73.10 74.20.1 (UPS, URS, UPS) is electrical device, which provides emergency power to the load in the event that the signal from the network is interrupted or weakened. A UPS differs from an auxiliary, emergency power, or standby generator in that it provides near-instantaneous protection from incoming power outages by supplying energy stored in batteries, capacitors, or flywheels.

The operating time of uninterruptible power supplies from a battery is relatively short (only a few minutes), but is sufficient to turn on a backup power supply or properly shut down the protected equipment. It should be noted that the stabilizer has other functions, but many people confuse them.

Generally, the most common use of an uninterruptible power supply in a home environment is for computer, hardware protection, data centers, telecommunications equipment, or other electrical applications where an unexpected power outage could result in injury, death, serious production disruption, or loss of data. (radio station, PC, laptop, database, server, automatic telephone exchange, pump, for gas heating boilers).

Server uninterruptible power supplies range in size from a single unit, to protecting a single computer without a video monitor (around 200 volt-amp rating), to large facilities powering entire data centers or buildings.

Area of ​​use

The primary role of any UPS is to provide short-term power when power input fails. However, most UPSs are also capable of adjusting to some extent common problems power supply from the network:

• Voltage surge or delayed overvoltage;
• Short-term or sustained drop in input voltage;
• Noise is defined as high frequency transition process or vibrations are usually introduced in a line nearby equipment;
• Network frequency instability;
• Harmonic Distortion: Defined as a departure from the ideal sine waveform on a line.

For industrial enterprises, three-phase uninterruptible power supplies are most often used high power, they can control huge systems, up to 1000va, represented by the brands Electronix, Compact, SUA1500RMI2U, APC (APS) Back-UPS ES 400VA.

Household appliances are often used for signaling.

Technical characteristics of sources:

1. Switching speed from 1 millisecond;
2. Work with any sinusoid;
3. They transmit power from 1 kW (FORT F55, RIP-12, BIRP-12/4) to several hundred (Resanta UBP-300, BBP-20, Shtil, UPSRT8000);
4. Low degree of electromagnetic interference and acoustic noise;
5. Can be installed on a rack;
6. Input current with reduced harmonic distortion;
7. They are engaged in converting electricity, stabilizing the load, and providing a constant current of 0.5 Amperes.

Video: simple DIY power supply

Types of stabilizers

Modern UPS systems fall into three main categories:

1. Online (Online, interactive);
2. Line-interactive (in standby mode);
3. Synchronous.

IN online UPS uses a "double conversion" method of taking alternating current, rectifying it into direct current to pass through rechargeable batteries (or battery compartments), and then the current becomes 120V/230V AC to power the equipment being protected. Typical protection time: 5-30 minutes.

L frost-interactive (inverter) UPS maintains the inverter in line and redirects DC batteries from normal charging mode to supply current when power is lost. In standby mode (“off-line”), the system load is powered directly from the input power and backup, this power scheme is called only if it is not possible to turn off the alternating power supply. Most UPSs below 1 kVA (uninterruptible power supplies for PCs IPPON, EATON) are a type of line-interactive device or standby uninterruptible power supply. The offline/backup device has a typical protection time of 0-20 minutes.

For large power units, dynamic uninterruptible power supplies are sometimes used. Synchronous motor/generator connected to the network via a choke. Energy is stored in the flywheel. When mains power fails, the eddy current mechanism provides regulation and maintains power to the load until the flywheel energy is depleted. Synchronous machines (Delta, Powerware, SURT10000RMXLI, TRUST power 600VA UPS155 AVR) are sometimes combined or integrated with a diesel generator, which turns on after a short delay, forming a diesel rotary uninterruptible power supply.

Standby UPS offers only basic functions, providing surge protection, they can replace backup battery. The equipment being protected is usually connected directly to the incoming power supply. When the input voltage drops below or rises above a predetermined level, the source rotates around its internal DC inverter circuit, converting it to AC. The UPS then mechanically switches the connected equipment to its current converter output. Switching time can take up to 25.

Many types of equipment use a battery to uninterruptible source power supply (IBM for a refrigerator), work with processors, some battery models for home or garden use are enclosed in a special sealed unit (Smart, Mustek, SUA2200RMI2U, SUA3000RMI2U).

Operating principle

The UPS introduces power using a converter, changing the flow of current through the circuit and then converting the DC current into a high-quality sine wave. After these manipulations, the energy goes to the output contacts through the inverter high quality. The inverter will provide smooth switching. It must be said that this method is short-lived.

The battery can quickly work with the inverter to change the alternating current to direct current. Such a system works only through a circuit. The main advantages are switching speed, quiet operation and affordable cost.

An automotive uninterruptible power supply most often has a dual function: it is used for video surveillance with autonomous operation, as well as normalization of voltage.

Instructions on how to make an uninterruptible power supply

Street or household source constant power supply It's quite expensive. We suggest you consider how to make an uninterruptible power supply with your own hands, how to select parts for the device and its possible purpose. Of course, in full compliance with branded devices We won’t be able to achieve this, but we can create a homemade small-sized source of several kilowatts for an apartment or country cottage quite real.

Description of independent production:

1. You can take spare parts from electronic devices (after a malfunction), we will need a battery of suitable power. You can buy it separately, but in this case it is better to consult a specialist;
2. Connect the inverter. It must be designed for long work and have a higher permissible kVA value than necessary;
3. Next we need a cable. You can use a power wire to connect the contacts of the inverter and the UPS board. It needs to be connected to the devices, secured and checked with a multimeter;
4. When working, it is very important to use protective suits and accessories (goggles, gloves, gas masks).

After we connect everything, we check the accuracy of the contacts, noting the polarity of each wire. After these steps, you need to place the UPS in a visible place, away from other devices, and turn it on. If desired, complement the device with a stylish case.

Such devices require special maintenance: cleaning contacts with solutions, checking the operation and level of cable transmission, and scheduled repairs every year.

Price overview

For many, it is easier to buy an uninterruptible power supply apc, okof, okpd or skat 1200, especially since the price allows it. Let's look at how much a UPS costs in Russia, Belarus and Ukraine (the price list has average values):

The most popular flywheel device now (wall-mounted or built-in type). Good reviews about single-phase IEC, dynamic Vision, INELT, Line, built-in APC. To clarify prices, you only need the product code and the sales consultant of the selected store. Always ask to see a quality certificate (diploma, passport).