The UPS model is the most adapted. Everything about uninterruptible power supplies for a computer. Uninterruptible Power Supplies On-Line Type
Uninterruptible Power Supplies Off-Line
Uninterruptible power supplies of type Off-Line are defined by the standard as passive, standby (UPS -PSO). In the normal operating mode, the standard power supply of the load is the filtered voltage of the primary network with permissible deviations of the input voltage and frequency. In cases when the parameters of the input voltage go beyond the values of the configured ranges, the inverter of the uninterruptible power supply is switched on, ensuring the continuity of the power supply to the load. The inverter is powered by batteries.
These are the simplest UPSs (Figure 1), and therefore the cheapest. The uninterruptible power supply consists of two parallel branches:
... filter load;
... rectifier-battery-inverter-load.
Fig. 1. Stand-By type uninterruptible power supply circuits
Under normal network characteristics, the voltage is supplied to the load through a filter that filters all kinds of interference. This is usually a surge suppressor, although it can be a line conditioner or a combination of both, as well as a static switch.
At the same time, the accumulators of the storage battery are also recharged through the rectifier. When the input voltage is lost, overestimated or lowered, the power supply of the load by an electronic switch is switched to the battery through the inverter (the inverter converts the constant voltage into alternating voltage). The switch provides switching times from 2 to 15 ms. Note that power outages during this time do not have any noticeable effect on computer systems that can easily tolerate a 10-20ms power outage. Considering that almost all modern equipment has impulse power supplies, switching is performed imperceptibly for the user. Uninterruptible power supplies of this type can support the operation of a personal computer for 5-10 minutes.
Main Disadvantages of Off-Line UPS
The main disadvantages of off-line UPS are:
... poor performance of power supplies of this type in networks with poor quality of the electrical network: poor protection against voltage dips (sags), exceeding the permissible voltage value, changes in the frequency and shape of the input voltage;
... impossibility of timely restoration of battery capacity with frequent switching to battery power;
... non-sinusoidal output voltage when powered by a rechargeable battery.
Uninterruptible power supplies such as Line-Interactive
Line-interactive uninterruptible power supplies (Line-Interactive, sometimes Ferroresonant) combine the advantages of the On-line type with the reliability and efficiency of standby ones. In uninterruptible power supplies of this type, in contrast to the Off-line technology, a step automatic voltage regulator (booster), built on the basis of an autotransformer (transformer with switching windings), is included in the direct circuit. Some models use a network voltage stabilizer.
The inverter is connected to the load. In operation, it supplies the load in parallel with the conditioned AC mains voltage. The load is only fully connected when the mains input voltage is lost.
Fig. 2. Line-Interactive Type Uninterruptible Power Supply Circuits
Because of this interaction ("interaction") with the input mains voltage, this architecture gets its name. Within a certain range of mains voltage variation, the output voltage is maintained within the specified limits by switching the transformer windings or by a stabilizer. The inverter typically operates at low voltage, regulates the output voltage and recharges the batteries until it needs to be turned on to fully power the load in the event of a power outage. Line-interactive uninterruptible power supplies are most widely used in computer network protection systems.
The transformer, made using a special so-called ferro-technology, smooths out voltage surges, while the uninterruptible power supply switches to battery operation less often, and therefore increases the battery life. Usually, these uninterruptible power supplies are equipped with sophisticated filters to provide protection against interference of various origins. Typical switching times to or from battery power are 2 ms.
Structurally, the transformer does not have several additional taps in the secondary winding (it can be an autotransformer with a single winding), the controller (microprocessor) controls the switching of the taps of the transformer when the input voltage changes, maintaining the output voltage in the required range. So, Line-Interactive uninterruptible power supply works on the principle of controlled LATR and really less often switches to battery power during input voltage surges. In this scheme, the charger is structurally combined with the converter.
One of the advantages of this type of UPS is the wide range of permissible input voltages.
In some line-interactive models there is a shunt circuit between the mains input and the load, such UPSs are called line-interactive shunt UPS (UPS -LIB, Reversible + Bypass). In shunt mode, the supplied load is not protected. When working with sources based on ferro technologies, you need to keep in mind:
Uninterruptible Power Supplies On-Line Type
On-Line technology allows you to implement the most reliable type of uninterruptible power supply. From the rectifier (Figure 3), the mains voltage is supplied to the high-level to low-level DC voltage converter, and then to the DC-to-AC output voltage converter (ПН2). Converter PN2 is an inverter, the power to which is supplied both from the batteries and from the network through the voltage rectifier-converter PN1, connected in parallel:
.
at normal input AC voltage, the PN2 inverter is powered from the rectifier;
... in case of deviations in the supply network from the norm, the input voltage for PN2 is removed from the storage battery.
Fig. 3. On-Line Type Uninterruptible Power Supply Circuits
In most UPS systems up to 5 kVA, instead of a continuous battery, a backup converter is connected direct current(DC-DC converter), which turns on in case of network failures and duplicates the DC bus from the low-voltage battery.
Conclusion: even in cases of slight deviations of the input voltage parameters from the norm, On-Line devices provide the rated output voltage in the range of ± 1-3%. The presence of a bypass circuit allows the load to be connected directly to the mains. The power quality and reliability of power supply provided by devices with this type of architecture is significantly higher than that of the previous ones.
Disadvantages of On-line uninterruptible power supplies: low efficiency (85 -90%) compared to the previously considered types due to double conversion (in relation to Standby and Line-Interactive) and high price. However, the level of protection of the load and the stability of the UPS output parameters is a reasonable compromise between safety, efficiency and cost of the device. Losses in a 4000VA UPS do not exceed 380W and can be incommensurate with the task that such a power source solves.
New modifications of uninterruptible power supplies
Now there are several new modifications of uninterruptible power supplies:
.
by-pass;
... triple-conversion;
... ferrups.
The first modification (by-pass), as in Figure 3, is an additional channel for transmitting electricity to the load, its presence allows for high reliability of the device. Switching to the On-line mode is performed automatically when the parameters of the output network deviate from the norm or in emergency conditions. Thus, this mode helps to increase the reliability of the device. The second modification (triple-conversion) contains a power factor corrector. In the third modification (ferrups), a ferroresonant transformer is used, which provides high reliability and a wide range of input voltages.
New approaches in the construction of uninterruptible power supplies are based on the use of redundant power systems, which have a higher reliability of the output network, so that a failure of one of the elements does not lead to the failure of the entire system. Usually this modular systems, designed either on the principle of increasing the load power, or to increase the reliability of the system, or using both principles together. The simplest system has an auxiliary module in the structure of the uninterruptible power supply, "isolated in hot standby mode". There are several options for technical solutions for such uninterruptible power supplies.
The first option is to use an automatic switch (Figure 4). The inputs of one or more power supplies are connected to a single network, and are connected to the load through an automatic switch. Information about the state of operation of the units, control commands are received via the communication channel of the integrating UPS.
Fig. 4. Parallel circuit using automatic switch
The second option contains a “load distributor” (Figure 5), which evenly distributes the load between the individual sources of the system.
Fig. 5. Parallel circuit using automatic switch
The third embodiment of the parallel structure (Figure 6) uses the principle of a two-tier system. In this method, one of the "master" modules controls the load sharing between the other "slave" modules.
Fig. 6. Parallel circuit based on two-level Master-Slave system
The fourth option, with a redundant parallel architecture, looks the most promising. In such a scheme (Figure 7), not only the modules are reserved, but also the connections between them, and, if necessary, any module can perform the functions of the master. Only such a scheme is characterized by an increase in power, the absence of shunt circuits, while continuous protection of the load with the help of a UPS is guaranteed.
Fig. 7. Redundant Parallel System Diagram
Main technical characteristics of uninterruptible power supplies
Supply voltage form
It is this characteristic of the uninterruptible power supply that is important for the load. In the UPS operation mode, the load can receive an output AC voltage close to a rectangular shape (meander), due to the smoothing properties of filters, an approximated sine wave and a pure sine wave. The closest to a sinusoidal waveform of the output voltage is obtained by applying pulse-width modulation. Obtaining a sinusoid as a supply voltage is typical only for On-line UPS and some Line-Interactive power supplies.
Power
Full or output power.It is designated by the letter S, the unit is VA or Volt-Ampere. It is the geometric sum of active and reactive power. The parameter is calculated as the product of the rms (rms) values of current and voltage. Its value is indicated by the manufacturer of the power supply.
Active power consumption of the load. Indicated by the letter P, the unit is watt (W). In the absence of a reactive component in the network, it coincides with the total power. It is defined as the product of the total power and the cosine of the angle φ, where φ is the phase angle of the linear voltage and current vectors, i.e. P = S. cos (φ). Typical cos (φ) value for personal computers is about 0.6-0.7. This quantity is called power factor. Obviously, in order to select the required power for an uninterruptible power supply, it is necessary to divide the load power in watts by the value of cos (φ).
Reactive - denoted by the letter Q and is calculated as the product of the total power S by the sine of the angle φ (Q = S. Sin (φ)). The unit of measurement is reactive volt-ampere (var). It characterizes the losses in the supply wires due to the reactive current loading them. At cos (φ) = 1, there are no losses, all the power generated by the power supply goes to the load. This is achieved through the use of passive compensating devices or active power factor correction.
Input supply voltage range
Input voltage range - defines the limits of acceptable voltage values in the network, at which the uninterruptible power supply is still able to maintain the output voltage without switching to battery power. For some models, this range is load dependent. For example, at 100% load, the input voltage range can be 15-20% of the nominal, at 50% load - this range is 20-27% of the nominal, and at 30% load - 40% of the nominal. The battery life depends on this parameter, the wider the range, the longer the batteries will last, all other things being equal.
Input voltage frequency
Input frequency - characterizes the range of deviation of the mains frequency. Under normal operating conditions, the frequency deviation from the nominal value usually does not exceed 1 Hz.
Distortion factor of the output voltage waveform
The total harmonic distortion (THD) characterizes the deviation of the output voltage from the sinusoid, measured as a percentage. Small values of the coefficient correspond to the shape of the output voltage, approaching sinusoidal.
Mode switching time
The mode switching time (transfer time) characterizes the inertia of the uninterruptible power supply, for different sources it is approximately up to 2-15 ms.
load) characterizes the stability of the uninterruptible power supply during power overloads, measured as a percentage in relation to the rated power. Determines the UPS's resistance to transient overloads.Battery life
The autonomy time is determined by the capacity of the battery and the size of the load. For typical low-power uninterruptible power supplies supplying personal computers, it is 5-10 minutes. This time is calculated so that the user can close all running applications while saving the information and turn off the PC in normal mode.
Crest factor
The crest factor is the ratio of the peak value of the consumed current to the average current. The value depends on the shape of the supply voltage.
Battery life
The service life of rechargeable batteries is 4-5 years, but the real one strongly depends on the operating conditions: the frequency of switching to autonomous mode, charging conditions, and the environment.
Cold start
The presence of a cold start is the ability to turn on an uninterruptible power supply in the absence of voltage in the supply network. This function is useful when you need to urgently perform any action, regardless of the presence of voltage in the mains.
UPS batteries
General information
The source, the energy of which is used to power the load in critical operating modes, is the storage battery. In uninterruptible power supplies with a capacity of up to 20 kW, as a rule, sealed lead-calcium batteries with a suspension type electrolyte are used. In batteries of this type, the electrolyte is immobilized, either by silica gel or by glass fiber, which makes them leakproof. This property of the electrolyte allows batteries to be operated in any position; moreover, they do not need periodic electrolyte replenishment and other maintenance.
The electrodes are made of a lead-calcium alloy, which provides a long service life and a wide range of battery applications, the operating temperature range is from minus 20 to plus 50 ° C (for some types of batteries). Batteries do not suffer from the so-called "memory effect", they can be stored for a long time in a charged state (up to a year), while the self-discharge current is insignificant.
Battery design
The design of the batteries is traditional - the shock-resistant plastic case is divided into sections - "banks". The sets of cathode and anode plates are separated by spacers - fiberglass separators. The active part of the electrolyte is sulfuric acid. The cover is hermetically connected to the body, without the possibility of disassembling the battery. In the upper part of the cover there are valves (one for each section), which ensure the release of gas in case of its excessive formation during operation, and lamellar outputs. The valves are closed with an additional removable cover.
Battery storage
The battery life is approximately 5 years. With daily use of an uninterruptible power supply, its own charging capabilities guarantee operation during this period. Batteries self-discharge if left unused. For YUASA batteries, the self-discharge rate is approximately 3% per month at an ambient temperature of approximately 20 ° C. If the batteries are not charged over a long period of time, lead sulfates form on the negative plates of the battery. This phenomenon is known as "sulfation". Lead sulfate acts as an insulator, preventing the battery from accepting charge. The deeper the plate is softened, the less charge the battery can take.
To exclude irreversible consequences during storage, it is necessary to carry out the charge after a period corresponding to the ambient temperature conditions. Long-term storage batteries should be recharged periodically to ensure optimal life.
UPS battery charging methods
Battery charging is a major part of its maintenance. The battery life depends on the efficiency of the selected charging method. The following charging methods are available:
- charging at constant voltage;
- charging at constant amperage;
- two-stage constant voltage charging.
The preferred method is constant voltage charging. In this case, the battery is connected to an energy source, the charging voltage of which is kept constant during the entire charging process. During charging, the current strength decreases and becomes much less than when charging by the constant current method, and at the end of the charge it drops to almost zero. In this case, the battery is charged to 90-95% of its nominal capacity.
Choosing an uninterruptible power supply
The range of types of uninterruptible power supplies as a means of protecting equipment and computer systems is quite wide. The choice of the required power source is very difficult. To decide the issue of choosing one or another UPS, you need to try to analyze the factors that affect the operating conditions of the power source.
First, one must try to assess the significance of the system being fed. It is quite possible that an Off-line or Line-interactive type uninterruptible power supply will be sufficient for a home or office option. On-line UPS is more suitable for a server computer and other types of load that have increased requirements for the quality and reliability of power supply.
Secondly, it is necessary to assess the quality of the power grid: the likelihood and frequency of power outages, the presence of voltage fluctuations and various interference.
Third, you need to evaluate the power of the uninterruptible power supply. In order to roughly imagine what power of the UPS is required, it is necessary to determine the protected equipment and calculate the total value of the consumed power for it. Then, the resulting watts must be converted to VA, dividing by the power factor. For computer equipment, the power factor is 0.5-0.6.
Manufacturers do not recommend loading an uninterruptible power supply more than 80% of its maximum load. It should be noted that it is not recommended to connect laser printers to an uninterruptible power supply due to the high power consumption of the heating element.
The state of power grids in our country is in such a state that voltage drops, especially in winter time, are the norm and few people attach importance to them. Everyone is used to living by consequences, not prejudices, and buy uninterruptible power supplies only when they already feel their importance in monetary terms when buying new, burnt-out equipment.
A little about this device
The nominal voltage fluctuation in the mains should not exceed 7% if the international standards are followed. But even they cannot predict and warn the client about:
- High frequency interference;
- Accidents at stations and wire breaks;
- Large deviations of the current frequency;
- Short-term or long-term surges / dips of voltage;
- Impulse high-voltage interference.
In this case, you can hope for "maybe", however, it is better to worry and secure your electrical equipment in the house using UPS UPS.
We watch the video, a little about the device, its correct choice:
How to choose the right UPS is not an easy question for the average person. Here, many factors are taken into account that influence the choice.
The main factors for choosing an uninterruptible power supply:
- Working hours;
- Switch response speed;
- Power;
- The presence of voltage filters.
How the UPS is connected
To properly connect an uninterruptible power supply, you need to determine which equipment in the house is most sensitive to surges. In an average apartment, this is a computer.
That is why they produce separate UPSs for PCs. Also, for safety, you can connect the most expensive equipment, but make sure that the power of the purchased device is sufficient to power it. The rest of the electrical appliances are connected through a conventional surge protector.
Types and types of equipment
Types of uninterruptible power supplies
The choice of device depends on the nature of the problem. There are three types:
- Reserve;
- Interactive;
- Industrial.
Reserve
Used when network interruptions and interference are rare. The price is very low, but the possibilities are not particularly encouraging.
During a power surge or lack thereof, this device switches the connected household equipment to battery mode.
Disadvantages:
- With continuous power surges, standby UPSs consume battery power too quickly and become ineffective. Of course, you can buy a battery for an uninterruptible power supply in any specialized store, but its cost is half or even 2/3 of the cost.
- The response time is quite long (about 1 second). In most cases, this will not affect the operation of small devices, but powerful devices will turn off, since the gap before switching is very large.
Interactive
Suitable when voltage drops occur very often. Average price and features are impressive to pay attention to.
The principle of operation is the same as for redundant UPSs. This UPS is suitable for circulation pump and other single industrial equipment.
Peculiarities:
- The response time is 0.2-0.5 seconds. This is enough to switch to battery mode without emergency shutdown of some powerful electrical appliances.
- The UPS equalizes the voltage before transferring. This gentle attitude to the battery will help preserve it for several years and save your budget.
Industrial type UPS
The most efficient devices for regulating the mains voltage. The pricing policy of assembling such a UPS does not allow it to be in the top in terms of price, however, the characteristics and capabilities deserve the price it costs.
For apc you will also have to pay a substantial amount, but they serve quite a lot.
Peculiarities:
- Real-time adjustment and switching.
- They are produced with very capacious batteries for an uninterruptible power supply, capable of powering professional equipment in factories or data centers.
Please note: Most uninterruptible power supplies require a ground connection and may not function without it. Some manufacturers are not responsible for the consequences if the purchased UPS was not grounded during operation.
Determine the power
Depending on its own power, the UPS is conventionally divided into 3 categories:
- Low-power (up to 1000 VA). They are used only to protect equipment and are not capable of maintaining operation for a long time. However, this power is enough to safely shut down the equipment.
- Medium power (1000-5000 VA). They are used to safely turn off the main equipment in the house or its work for up to 1 hour (depending on the number of connected equipment and its power). Weak equipment can operate for several hours.
- Universal (from 5000 VA). The cost of such UPSs is too high, but they are enough for the full operation of all equipment in the house or in a small production. The price of a battery for an uninterruptible power supply depends on the power, and it determines the life of all connected equipment.
IPB power calculation table
When buying a UPS, you need to clearly understand the basic rule of any equipment for backup power: the power of the device is selected according to the principle of summing up the power of electrical equipment with a surcharge of 20-30% of the stock. It is necessary for devices that periodically switch to an active mode of energy consumption (refrigerator, microwave oven, electric kettle). In addition, the stock is useful when buying new electrical equipment or replacing an old one.
How to calculate the required power correctly
You may have noticed that the UPS displays the wattage as "VA" (Volt-Amperes). So it is customary to designate full power any equipment that powers electrical appliances (generators, power plants, UPS). Appliances indicate active power in watts (W). To convert watts to volt-amperes, multiply them by 1.3.
Let's give an example:
The microwave consumes 800 watts. To find out how much volt-ampere she will use, multiply 800 by 1.3. We get 1040 VA.
Please note: the above surcharge is not necessary to convert watts to vol-amperes, but in order not to accidentally overload the UPS by supplying it with more power than it can handle. Therefore, the figure in watts needs to be increased by 50-60%.
Features and rules of equipment maintenance:
The warranty period of an uninterruptible power supply is a very important indicator of its quality. However, even high-quality devices can sometimes fail at the most unpredictable moment and the phrase: "3 months - normal flight, and will continue to live" - will not fit this equipment. Before buying, check the availability of the manufacturer's service centers in the city.
Controllability is a good feature, especially on expensive UPSs. Some of them support control via a USB cable connected to a PC. If such a function is unnecessary, you can opt out and save a small amount of money.
The article discusses the types of UPS, the principles of UPS operation, and also provides real oscillograms of the output voltages.
To begin with, some general terminology. Uninterruptible power supplies (UPS) are also called UPS, from the English abbreviation Uninterruptable Power Supply. Therefore, they say both UPS and UPS, as it is more convenient to whom. In the article I will call it this way and that.
Why do you need a UPS (UPS)
The principle of operation of the UPS is disclosed in the name - it is such a source, at the output of which there is always tension... But we have gathered here realist techies, and we understand that nothing is eternal, so below we will understand the principle of action.
UPSs are mainly used where power outages can cause negative consequences. For example, power supply of computers and servers, power supply of communication and signal distribution devices (routers), power supply of devices, automatic reboot (restart) of which is impossible without human intervention.
How my reader modified a UPS for a strategically important system (2 servers, etc.). In addition, he improved the circuit, and added the ability to use a conventional car battery.
For household items, these are primarily computers and heating systems.
It should be understood that UPSs are selected for a load operating time of 10-15 minutes, rarely up to half an hour. It is assumed that during this time, power will appear, or a person (operator) will take the necessary actions (save the data, call the energy service of the enterprise, complete the technological process).
The UPS should not be considered as a backup power source. It is only an emergency source, and at best it is used very rarely, for a total of no more than 10 minutes a year (several times, for no more than a minute). If this time is longer, then you should think about improving the quality of power supply.
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A backup power source can be considered such sources that can completely replace the main power supply for a long time, from several hours to several days. It may be another line (see article about), a wind generator. Theoretically, a UPS can also serve for these purposes, but this requires batteries of enormous capacity, which will significantly affect the price of such a system.
Types of uninterruptible power supplies
The types (types) of UPS have many names, but there are still exactly three of them. Let's figure it out.
So, there are three main types of UPS:
Back UPS
Other equivalent names are Off-line UPS, Standby UPS, and standby UPS. The most common OOIs are used for most types of household and computer equipment.
Back simply switches the load to battery power when the input voltage goes out of range. The lower limit for different models is about 180V, the upper limit is about 250V. Transitions to the battery and vice versa - with hysteresis. That is, for example, when lowering, the transition to the battery will take place at 180 V or less, and vice versa - at 185 or more. The same principle applies to all types of UPS.
Something like that disconnects load, and Back UPS does not turn off, but switches on the battery, which allows her to work for some time.
Smart UPS
Other names - Line-Interactive, interactive type UPS. We are not far from Back on the principle of action.
Smart UPS are smarter, as the name suggests. They additionally switch the internal autotransformer, in a sense, stabilizing the input voltage. And only as a last resort they switch to the battery.
Thus, the output voltage norm is maintained at large input deviations (150 ... 300V). The autotransformer has several switching stages, so the Smart UPS switches the autotransformer outputs until the last moment, including the battery only at the last moment. This saves the battery by turning it on only when the power is completely lost.
This device resembles the stepwise switching of the autotransformer windings. The only difference is that when it goes beyond the operating limits, the stabilizer will be powerless, and our “clever girl” will put the battery into operation, and the power will not be lost.
Online UPS
Other names are online, double conversion uninterruptible power supply, inverter. A completely different principle of action, for lovers of pure sinus. The energy from the input is converted to DC voltage and fed to the inverter, which generates a pure sine wave. And at the same time - it keeps the battery at 100% readiness. If necessary, the inverter continues to operate in the same way, only the power is supplied to it from the battery.
It is used for emergency power supply of equipment that is sensitive to the shape of the output voltage - for example, gas boilers, servers, professional audio-video equipment and other strategically important equipment.
There are two disadvantages of online UPS - price and efficiency. The efficiency is low, because such a UPS is included in operation all the time, as the name implies. Unlike the other two types.
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There are varieties of online UPS, which use the so-called "pass-through zero" for the correct operation of gas electric boilers. This is due to the fact that such boilers are sensitive to the presence of a real zero, for proper ignition.
Examining the UPS with an Oscilloscope
And now - the fun part.
Back UPS Output Voltage
Conducted a study using a Fluke 124 oscilloscope. Oscillograms (shape of pulses and oscillations at the output of ups) are presented and commented on below.
What does this timeline show? Period 20ms, frequency 50Hz, amplitude 315V. It is worth noting that the phase of the sine and the generated pulses are the same, which is good. When the mains voltage is lost, the UPS hesitates for 5-7 ms, and then there are pulses, which are called "quasi-sine". Here they are:
Back UPS. Output voltage when powered by batteries.
The oscilloscope has measured the RMS voltage (root mean square), it is correct. However, when I measured the same voltage with a multimeter, I got a reading of 155 V. Why is the UPS output low?
The fact is that the multimeter measures only the first harmonic with a frequency of 50 Hz. For the sine, everything is smooth. But if you measure the voltage of such pulses, you need to measure exactly RMS, rms, otherwise the following harmonics will not be taken into account - 100, 150, 200 Hz. And they make up a significant part of the energy, up to 30%. UPS manufacturers know this feature, and in order not to bother (and not to raise the price of their products), they issue such pulses to our devices with an amplitude of about 370V.
For more information on measuring the RMS non-sinusoidal voltage, see the video:
Here is an enlarged graph, where you can see that the voltage after switching first rises for half a second to 400V, and then stabilizes:
Back UPS. Exit, duration 2 seconds
And here is how the voltage waveform at the Back-UPS output changes at the moment of switching from battery to mains supply:
Back UPS, - UPS output voltage when transferring from battery to utility. The shape of the pulses at the output of ups
The phase also does not change, everything is fine. I connected the UPS to the output, switched power modes back and forth - the starter is pulled in securely, no problem.
The subject was an APC Back-500-RS UPS, the parameters are in the photo below:
Back UPS Options - Rear Panel
Smart UPS Output Voltage
Now I will give for completeness a picture of the voltage oscillogram at the output of Smart UPS. The UPS Ippon Smart Power Pro 1000 was tested.
Smart UPS_Grid-Battery
The switching time is also insignificant for all modern equipment - less than 7 ms.
I did not smoothly change the voltage at the input, since there was no such goal. I believe that in this case, the Smart UPS behaves in the same way as a relay voltage stabilizer.
These studies were carried out as part of a project on an industrial refrigerator.
Convert the voltage of the 220 V network to the desired values, extend the performance of the computer and ensure the safety of data- main goals . Protection against power surges, sudden outages and the ability to use a backup source are very important for the normal functioning of all components of the device.
Buying an uninterruptible power supply for a computer means save on and do not worry about premature failure of your device.Our networks do not always give out the declared voltage of 220 V, even if emergency situations are a rarity, then stabilization of the mains current to normal values is possible only with the help of an uninterruptible power supply. Among the variety of UPSs offered, it is easy to get confused. How to choose the right UPS?
What are
All produced blocks can be conditionally divided into three types:
- Reserve... USP low power. The main function is switching to battery power during battles in the network and vice versa when the voltage is normalized;
- Interactive... They are most commonly used for home and office computers. The device has a stabilizer that gives a sinusoidal voltage at the output;
- Online power supply units... During their operation, a double voltage conversion occurs. The input alternating current is converted to direct current, and the inverter converts it back to alternating current. Used for large DNS servers and stations.
In the medium and high power units, there is a special device for connecting the input and output directly, without using the backup power, which is called bypass. In the event of overloads, the power from the inverter is routed to the bypass, which saves current consumption.
The correct selection of the block includes selection by power, type and purpose of use.
Some calculations should be done before purchasing. For the coordinated operation of the entire system, it is necessary to select the correct power unit corresponding to the parameters of your devices. General principle calculation - the total power of all computer devices should not exceed the power of the UPS. The capabilities of the power supply depend on its output power, which is measured in volt-amperes and is calculated by multiplying the voltage by the amperage.
The main purpose of an uninterruptible power supply (UPS) is to temporarily provide power to equipment during power outages. It is common practice to connect computers via UPS. True, for many users this is a kind of "good form" rule, and the practical meaning of this ritual eludes them. "Well, the UPS protects the computer from power surges ...". Let's try to figure it out: what, from what and how does the uninterruptible power supply protect?
According to the internal structure and logic of operation, all UPSs are divided into three classes: passive, line-interactive and double conversion UPS. Accordingly, they cope with incidents in the power grid to varying degrees and belong to different price categories.
Passive(stand-by, VFD, back-UPS, standby) sources are the simplest and cheapest. In them, the battery power circuit is usually turned off, and starts only when there is a power outage. The switching time from mains operation to battery operation is tenths of a second, and the output signal when operating on battery power differs markedly from the "correct" sinusoid. As a rule, a simple noise filter and a high-speed fuse are installed at the input of such UPSs. The first partly smooths out the impulse noise, and the second should work with a significant increase in the voltage in the mains. Passive UPSs are designed to power home and office PCs. A small "dip" in the output voltage at the moment of switching to the battery is not terrible for computer power supplies.
Line-interactive(line-interactive, VI, Smart-UPS) UPSs differ in that the battery power circuit is always on. When the voltage at the UPS input fails, its output sockets are almost instantly switched to the internal converter - for powered devices this transition is almost invisible. In addition, many line-interactive UPSs are capable of automatically supporting 220V output. This is done in two ways.
While the mains voltage is in the range from 175 to 275 V, the AVR (Automatic Voltage Regulation) mechanism is triggered. If the input voltage deviates from 10 to 25% below the rated value, the UPS increases the output voltage by 15%. When the input voltage deviates from 10 to 25% above the rated value, the UPS will lower the voltage by 15%. If utility voltage is out of range, the Line-Interactive UPS transfers to battery power. In this mode, it continues to work until either the voltage in the network returns to normal, or the battery is discharged. However, such UPSs should not be considered as voltage stabilizers. They have a forced and short-term "stabilization" mode!
V Double Conversion UPS(double conversion, VFI, Online-UPS), the output voltage is always supplied from the converter, the converter is constantly running on battery power, and the battery is continuously charged from the mains. In fact, the input and output of the UPS are galvanically isolated from each other, and a stabilized voltage is supplied to the output. This is the most reliable, but at the same time uneconomical scheme. The UPS itself turns out to be expensive, large and heavy, the converter gets very hot and requires cooling with a fan, and the energy losses during the conversion amount to tens of percent.
A double-conversion UPS is used only to power servers and computers in critical applications. Such models rarely go on sale on a large scale - they are usually delivered to order. Most likely, you will purchase passive, maximum, line-interactive UPSs to power your work computers.
The power of uninterruptible power supplies is usually indicated in volt-amperes (VA, VA). To convert these values into more familiar watts (W), you need to multiply the power in volt-amperes by a factor of 0.6. For example, a UPS with a 600 VA rating will supply power to a technician with a maximum consumption of 360 W. If you give a large load, the current protection will work, and the "uninterruptible power supply" will turn off. In practice, it is desirable to provide for about 30% of the power headroom. Thus, the most common 600 or 650 VA UPSs are suitable for powering a computer with an actual consumption of 200-250 W and a monitor that draws another 30-60 W.
If the arrangement of computers in the room allows, it is more profitable to use one powerful UPS instead of several small ones. Two office computers will require an uninterruptible power supply with a capacity of about 1000 VA. To power three computers standing side by side, one power supply with a capacity of about 1400 VA is sufficient.
So what does the UPS protect against?
Filters in the power supply unit of the computer and monitor do a good job of limiting impulse noise from the network. However, two filters are better than one! Overvoltage protection is also important. If, for example, the neutral wire in the shield burns out, a voltage of almost 380 V may appear in the outlet. In this case, varistors and fuses usually burn out in the power supplies of computers and monitors. Repair is cheap, but it takes time. In theory, the UPS should react to a voltage surge before the fuses in the equipment connected to it burn out.
However, data protection comes first. If the computer is powered off abnormally, all unsaved information is lost. The UPS allows you to either save open documents and shut down gracefully, or put the computer into sleep mode. It is easiest to save documents manually. Switching to battery power, the UPS starts beeping loudly. Once you have heard such a warning, check if everything is saved. Then look at the situation: either just turn off the computer, or put it into sleep mode.
To activate the automation, you need to connect the control port (USB or RS-232, depending on the model) of the uninterruptible power supply to the computer with a signal cable and install the necessary software on the computer. Unfortunately, many users are not even aware of this possibility! The UPS is controlled by an integrated microcontroller. Its firmware (firmware) constantly monitors voltages and currents in external circuits, when switched on and periodically during operation, it performs tests of electronics and batteries. It also sends information to the control port about the current operating mode, the state of the UPS components. These data are fed through the cable to the computer, where they are processed by the monitoring program.
To work with the UPS, it is advisable to use the program offered by its manufacturer. For example, for APC (www.apc.com) this is the Power-Chute program, for Ippon (www.ippon.ru) - WinPower2009 and Ippon Monitor, etc. The program can be installed from the included disk, but it is better to download the most its fresh version from the manufacturer's website.
In the application settings, you need to set the automatic shutdown parameters. As a rule, there are two options to choose from: either turn off the computer after a certain time after switching to backup power, or do it some time before the expected complete discharge of the batteries.
How long is the uninterruptible power supply able to work from the battery?
It depends on the battery capacity and power consumption. Most mass-produced models have one battery with a voltage of 12 V and a capacity of 7 Ah. In theory, a UPS with such a battery has a power reserve of about 80 Watt-hours. Simply put, it should power a load of 80 W for about 1 hour, 160 W for half an hour, 300 W for about 15 minutes, etc. In reality, taking into account the conversion losses, this time is about half.
Sources with a capacity of more than 800 VA usually have two of the same batteries or one, but with a larger capacity. Tables or calculators for determining the battery life at different loads for different models are given on the manufacturers' websites. However, "offhand" it can be assumed that any model will be able to supply a load of its rated power for about 5-15 minutes. If you need to provide a sufficiently long power supply of the computer from batteries, it is better to take a high-power UPS with capacious batteries. It will work at only a third or a quarter of the rated power. But such a load, low for himself, he will be able to supply with energy for half an hour or longer.
For network equipment (switches, routers, NAS), uninterruptible power is also useful. Otherwise, when the power is turned off, the network will immediately "fall", and documents opened from network folders cannot be saved. You can power the switch from the UPS of the workstation closest to it, although it is more correct to put a separate "uninterruptible power supply" of low power for this.
Battery life is limited. As it works, its capacity steadily decreases and after 3-5 years of operation it drops to almost zero. Even before the indicator on the UPS signals the need to replace the battery, it becomes noticeable that the battery is no longer “holding charge”. The battery life gets shorter each time. In principle, a couple of minutes are enough to save documents and shut down the computer correctly. When the UPS starts shutting down even earlier, the battery should definitely be replaced.
Replacing the battery is easy. Popular APC brand UPSs and some others have the battery under a removable hatch or cover. To get to the battery in Ippon, SVEN and similar UPSs in design, it is necessary to unscrew the four screws on the bottom and separate the halves of the case. In the instructions and on the official website, you are unlikely to find a description of self-disassembly and replacement: like printer manufacturers, UPS manufacturers receive a significant share of their income from the sale of "original" batteries with their installation in authorized SCs.
Nonetheless, nearly all computer stores sell the most commonly used sealed lead-acid batteries. The brand and manufacturer do not play a role: these are quite standard products. First open your "uninterruptible power supply" and find out which battery is installed in it. For most UPS "office class" (500-700 VA) batteries marked 12V 7Ah with dimensions 151 × 94 × 65 mm are suitable. When installing a new battery, try to fit the terminals tightly over the battery contact tabs. If the terminals are loose, you can gently tighten them with pliers.
After installing the battery, it is advisable to calibrate the UPS so that its firmware will evaluate and remember the parameters of the new battery. Charge the battery fully within 24 hours. Then remove the plug from the socket to transfer the UPS to autonomous power supply. Let the battery drain completely until the UPS shuts down by itself. As a load, it is better to use not a computer (although in extreme cases this is also permissible), but several bulbs with a total power of about 300 watts. Then reconnect to the mains and turn on the UPS - let the battery charge, and the device will continue to work normally. In addition to calibrating the device as a whole, this procedure is also "training" the battery. After a complete discharge-charge cycle, the battery begins to use its capacity to the maximum.
Why do many UPSs have telephone (RJ-11) and network (RJ-45) sockets?
Neither telephone nor the local network"Uninterruptible power supplies" are not needed by definition. Just as a "bonus", in the same case as the device, there are pass-through filters of impulse noise for the telephone line and the network. Connect one jack to the telephone jack on the wall and plug the telephone into the other. If a high voltage pickup occurs on the telephone line, for example, during a thunderstorm, the filter will smooth out the voltage surge and protect the phone.
