UPS operating modes. Uninterruptible power supplies (UPS), what they are and their operating principle

Increasing requirements for the quality of electricity at the present time is a completely natural process. The requirements of the mentioned standards are determined by two components. The first includes the desire of consumers to protect themselves as much as possible from the consequences of emergency situations in the energy system. The second component is related to the operating conditions of the load. This should include the requirements for stable and continuous operation intelligent and power electrical equipment, reducing losses in the power supply network, etc. One of effective options technical solutions to the problem of power quality - uninterruptible power supplies (UPS).

The main task of the UPS is to provide the consumer with electricity at the moment when the quality parameters fall outside the regulated standards (sag, voltage increase, significant distortion of the shape...). By performing this task the UPS can:

• disconnect from the power supply and transfer power to the load using your own source;
• supply the load with the adjusted mains voltage.

In more expensive UPSs, a function for improving the quality of consumed electricity can be implemented (a power factor corrector is integrated).

Types of "uninterruptible power supply"

There are three basic types of UPS.

1. Backup UPS(standby, offline, back-ups). The simplest and cheapest technical solution(for example, the popular APC Back-UPS CS 500). If the voltage is significantly increased or decreased, the UPS is disconnected from the 220V network and switches to battery mode. The main elements of an offline UPS: batteries (battery), charger, inverter, step-up transformer, control system, filter (Fig. 1).
   
   
   A)
   
   
   b)
   Rice. 1 Normal operating mode (a) and battery operating mode (b) The advantage of an offline UPS is its low cost and high efficiency when operating from the network. Disadvantages: high level of output voltage distortion (high harmonic distortion, ≈30% in case square wave), lack of ability to adjust input voltage parameters. The output voltage characteristics will be discussed in more detail below.).
2. Interactive UPS(eng. line - interactive). It is an intermediate type between a cheap and simple offline UPS and an expensive multifunctional online UPS (for example, ippon back office 600). Unlike an offline UPS, the interactive source has an autotransformer that allows you to maintain the output voltage level within 220V (+-10%) during drops/increases in mains voltage (Fig. 2). As a rule, the number of voltage levels of an autotransformer ranges from two to three.
   
   
   (A)
   
   
   (b)
   
   
   (V)
   
   
   (G)
   Rice. 2 Operation of an interactive UPS at normal mains voltage (a), during a sag in mains voltage (b), at increased mains voltage (c), during the disappearance of mains voltage or a significant increase (d) The output voltage is adjusted by switching to the appropriate tap of the transformer winding. In case of a deep sag or a significant increase or complete disappearance of the mains voltage, this class of UPS functions similarly to the offline class: it is disconnected from the mains and generates output voltage using the energy of the batteries. Regarding the shape of the output signal, it can be either sine or rectangular (or trapezoidal).
   Advantages of line - interactive in comparison with a backup UPS: shorter switching time to battery-powered operation, stabilization of the output voltage level. Disadvantages: lower efficiency when operating from the network, higher price (compared to the offline type), poor filtering of surges (pulse overvoltage).
3. Double conversion UPS(English: double-conversion UPS, online). The most functional and expensive type of UPS. Uninterruptible power supply is always connected to the network. The input sinus current passes through the rectifier, is filtered, and then inverted back to AC. A separate DC/DC converter can be installed in the DC link. Since the inverter is always running, the delay to switching to battery mode is virtually zero. Stabilization of the output voltage during sags or dips in the mains voltage is of better quality, in contrast to the stabilization of the line - interactive UPS. Efficiency can be in the range of 85%÷95%. The output voltage often has a sine wave form (harmonic distortion<5%).
   
   
   Rice. 3 Functional diagram of one of the online UPS options in Fig. Figure 3 shows a block diagram of the online UPS option. The mains voltage is rectified here by a semi-controlled rectifier. The pulse voltage is filtered and then inverted. Online UPS schemes may contain one or more so-called bypasses (bypass switches). The function of such a switch is similar to that of a relay: switching the load for power from the battery or directly from the network.
   Based on the online structure, not only low-power single-phase, but also industrial three-phase UPSs are created. Continuity of power supply to large file servers, medical equipment, and telecommunications is carried out exclusively on the basis of the online UPS structure.
4. Special types of UPS. Other specific types of UPS are also used. For example, a ferroresonant uninterruptible power supply. In this UPS, a special transformer accumulates a charge of energy, which should be enough to switch power from the mains to the batteries. Also, some UPSs use the mechanical energy of a superflywheel as an energy source.

Main characteristics of the UPS.

1. Power. Power units: volt-ampere (VA), watt (W), volt-ampere reactive (VAr). Recall that there is total S, active P and reactive Q power. Equation relating powers
   S2=P2+Q2
   Active power(W) is spent on useful work, reactive (VAr) - does not perform useful work. Accordingly, total power, by definition, is the maximum power that the source must have to provide the load with the necessary energy. The ratio of active power to total power shows the quality of electricity use and is called power factor (PF):
   (incandescent lamps, heaters) has PF=1, the total power is equal to the active one. PCs, microwave ovens, air conditioners have a calculation example.
   Calculate an uninterruptible power supply for a computer (two PCs + two monitors). It’s easy to estimate the power of a PC if you know how much power the power supply is designed for. Let the PC have power supplies of 450 W (active power). If PF is unknown for a PC with a power supply without PFC (Power Factor Corrector), PF can be taken equal to 0.65. Similarly, we take the PF of the monitor equal to 0.65. The active power of the monitor is 50 W. As a result, the total active power of the consumer (two workplaces)
   Р=450+50+450+50=1000 W
   Total power (from formula 2):
   S= Р/PF=1000/0.65=1538 (VA).
   If a power factor corrector (PF=1) is installed in the power supplies (PSU) of the PC and monitor, then the total power S is equal to the active one.
   S=P=1000 (VA)
   For a PC load, you can calculate a UPS without power reserve based on the following facts:

• Computer power supplies have overload protection. In other words, the PC will not be able to consume more power than the declared power of the power supply.
• Power supply power – maximum power. In fact, in unloaded mode (immediately after startup), PCs consume about 50% of their power.

Result.
So, the required minimum UPS parameters are:

• for PCs with power supplies without PFC – 1 kW / 1540 VA.
• for PCs with power supplies with PFC – 1kW/1kVA.

For the first option, an uninterruptible power supply apc Smart-UPS C 2000VA (linear interactive UPS 2 kVA / 1.3 kW) is suitable. For the second - UPS Ippon Smart Winner 1500 (1.35 kW) or Eaton 5SC 1500 VA (1.05 kW).
When calculating, it is important to take into account short-term power increases for loads such as electric motors. At the moment of starting, the current Istart is five, seven times higher than the rated In:
Istart=(5÷7)*Iн

Features of application.

Uninterruptible power supplies for heating boilers, as well as uninterruptible power supplies for gas boilers, have a feature associated with the operating modes of the neutral conductor. Often, boiler automation requires connecting the network neutral. The fact is that the burner flame control circuit is connected to ground and in a four-wire 220V network, the neutral conductor and the boiler ground are ultimately closed through the physical ground. However, if the neutral is broken or the consumer zero is mechanically disconnected from the power supply network zero (offline UPS operation), the flame control circuit is broken. The following solutions are possible to resolve this issue:

conclusions

The starting point for choosing an uninterruptible power supply is determining the nature of the load (UPS for a computer, for heating boilers...). For critical consumers and devices containing AC motors, you should choose expensive and functional online UPS. For PCs and office equipment, cheaper line-interactive or back UPS are suitable. The next choice is to calculate the power and battery life of the UPS. The possibility of using a “through” zero should also be provided. When forming the final decision, one should take into account the popularity of brands in the market: the leader APC owns about 50% of all sales, followed by Ippon, Eaton Powerware, and Powercom with a significant margin.

Industrial solution: The UPS, together with the protected equipment, is mounted in a 19-inch rack

Uninterruptible power supplies have evolved in parallel with computers and other high-tech devices to provide reliable power to this equipment, something that standard power networks cannot provide. :128 The most common designs are as a separate device, including a battery and a DC-AC converter. Flywheels and fuel cells can also be used as a backup source. Currently, UPS power is in the range of 100 W ... 1000 kW (or more), different output voltages are possible. :142

Reasons for use

Short-term disruptions to the normal operation of the electrical network are inevitable. Most short-term power outages are caused by short circuits. It is almost impossible to completely protect the electrical network from them, or, in any case, it would be very expensive. :With. 6 Short-term power interruptions occur much more often than long-term ones. Long power interruptions can be avoided using automatic transfer transfer (ATS). In this case, short-term power interruptions will occur not only in the event of a short circuit on any of the lines supplying the ATS, but also on the lines supplying neighboring consumers. :With. 8

Uninterrupted power supply differs from guaranteed power supply in that in the case of guaranteed power supply, a break is allowed during the commissioning of the backup source. In the case of uninterruptible power supply, “instant” activation of a backup source is required. This important requirement limits the range of backup sources suitable for use in uninterruptible power supplies. In practice, usually only one such source can be used - a rechargeable battery.

The main function of a UPS is to ensure continuity of power supply through the use of an alternative energy source. In addition, the UPS improves the quality of the power supply, stabilizing its parameters within the established limits. UPS usually uses chemical current sources as energy storage. In addition to them, other storage devices can be used. :P. 1.1 The primary source can be power supplied from the mains or generator. :P. 3.1.3

Industry

Complex technological equipment of modern industrial production cannot function normally if the power supply is not uninterrupted. For many industrial plants, a power interruption of a few seconds or even tenths of a second leads to disruption of the continuous technological process and to a shutdown of production. :With. 5

If the permissible power interruption time is less than 0.2 s, only the use of uninterruptible power supplies is possible; protection by circuit breakers with short circuits to reduce the power interruption time is in this case impossible or ineffective. If the permissible time is more than 0.2 s, it is possible to use power supply protection or use uninterruptible power supplies. With an acceptable time of 5...20 s, it is possible to abandon uninterruptible power supplies and use an automatic transfer switch. :With. 61

For electric motors, voltage dips in a 0.4 kV network lasting 0.3...0.5 s can lead to the fact that the residual EMF vectors of electric motors may be out of phase with the network voltage vectors. As a result, when power is restored, the electromagnetic releases of the circuit breakers will operate and the electric motors will be completely turned off. At the same time, voltage dips lasting less than 0.3 s do not pose a danger, therefore, for electric motors, the fight against voltage dips is usually aimed at preventing contactors from disconnecting in the 0.4 kV main power circuit. One such measure is to power the contactor control circuits from an uninterruptible power supply. :With. 251

The susceptibility of industrial controllers on logic chips to voltage dips is similar to the susceptibility of computers. :160

Malfunction of contactors and relays can occur when the voltage is interrupted for 5...10 ms and 80...120 ms. The difference in operation of the same device arises from the difference in the instantaneous magnitude of the AC voltage when the voltage dip begins. When the voltage passes through zero, the stability is more than 10 times greater. :165

At home and in offices

The most common application in everyday life and offices is to turn off the computer without losing data during a power outage. When voltage dips lasting 0.2 s, the computer read/write procedures stop; 0.25 s - blocking of the operating system; 0.4 s - reboot. :158

Emergency

Power supplies that are used in case of interruption of normal power supply are divided into backup and power supplies for safety systems.

Regulation

The International Electrotechnical Commission has adopted a group of standards:

International classification of UPS

The history of electronic AC UPSs begins with the invention of thyristors in 1957. In 1964...1967 UPSs with redundant power up to 500 kVA were created. To date, the main change in design has been the replacement of thyristors with IGBT transistors. :130

Backup scheme

Disadvantages: in the “on-line” mode it does not perform the function of filtering peaks, and provides only extremely primitive voltage stabilization (usually 2-3 stages of an autotransformer, switched by relay, the function is called “AVR”).

In the “battery mode”, some, especially cheap, circuits output a frequency much higher than 50 Hz to the load, and an alternating current oscillogram that has little in common with a sine wave. This is due to the use of a large classic transformer in the circuit (instead of an inverter using semiconductor switches). Due to the fact that a transformer of this size has (due to the occurrence of hysteresis in the core) a limitation on the transmitted power, which increases linearly with frequency, this transformer (occupies 1/3 of the volume of the entire UPS) is enough to power the battery charging circuit at 50 Hz in “online” mode. But, in the “battery mode”, hundreds of watts of power must be passed through this transformer, which is only possible by increasing the frequency.

This makes it impossible to power devices that use, for example, asynchronous motors (almost all household appliances, including heating systems).

In fact, such a UPS can only power devices that are undemanding in terms of power quality, that is, for example, all devices with switching power supplies, where the supply voltage is immediately rectified and filtered. That is, computers and a significant part of modern consumer electronics. You can also power lighting and heating devices.

Double conversion circuit

Double conversion mode (English online, double-conversion, online) - is used to power loaded servers (for example, file servers), high-performance local area network workstations, as well as any other equipment that places increased demands on the quality of the network power supply. The principle of operation is double conversion of the current type. First, the input AC current is converted to DC, then back to AC using an inverse converter (inverter). If the input voltage fails, switching the load to power from the batteries is not required, since the batteries are constantly connected to the circuit (the so-called buffer mode of battery operation) and for these UPSs the “switching time” parameter does not make sense. For marketing purposes, the phrase “switching time is 0” can be used, which correctly reflects the main advantage of this type of UPS: the absence of a time interval between the loss of external voltage and the start of battery power. Double conversion UPSs have low efficiency (from 80 to 96.5%) in on-line mode, which is why they have increased heat generation and noise levels. However, modern medium- and high-power UPSs from leading manufacturers have a variety of intelligent modes that allow automatic adjustment of the operating mode to increase efficiency up to 99%. Unlike the two previous circuits, they are capable of adjusting not only voltage, but also frequency (VFI according to IEC classification).

Advantages:

• no switching time to battery power;
• sinusoidal output voltage, that is, the ability to power any load, including heating systems (which have asynchronous motors).
• the ability to adjust both voltage and frequency (moreover, such a device is also the best possible voltage stabilizer).

Flaws:

• Low efficiency (80-94%), increased noise and heat generation. Almost always the device contains a computer-type fan, and therefore is not silent (unlike a line-interactive UPS).
• High price. About two to three times higher than line-interactive.

DC UPS

UPS Specifications

Design

Electrical storage devices

Chemical

The implementation of the main function is achieved by operating the device from batteries installed in the UPS housing, under the control of an electrical circuit, therefore, any UPS, except control circuits, included Charger, which ensures that the batteries are charged when there is mains voltage, thereby ensuring that the UPS is always ready to operate in stand-alone mode. To increase the battery life, you can equip the UPS with an additional (external) battery.

Uninterruptible power supplies can use chemical current sources (CHS):

Dynamic

Capacitors

When using a DC ATS using a relay circuit, you can use a large capacitor to avoid power interruptions during switching. :With. 229

Bypass

A bypass is one of the components of the UPS. Bypass mode (eng. Bypass, “bypass”) - powering the load with filtered mains voltage, bypassing the main UPS circuit. Switching to Bypass mode is performed automatically or manually (manual switching is provided in case of preventive maintenance of the UPS or replacement of its components without disconnecting the load). Can do so-called phasanul (“through zero”). It is used in online circuits; moreover, when the online UPS is turned off by the OFF button, it remains in bypass mode, the same thing happens when the power components of the circuit are destroyed, determined by the control circuits, as well as when the circuit is switched off in an emergency due to an output overload. In line-interactive UPS, the “on-line” operating mode is the bypass.

AC voltage stabilizer

Used in UPSs that operate on an interactive basis. Often the UPS is equipped only with a booster, which has only one or several steps of increase, but there are models that are equipped with a universal regulator that works both to increase (boost) and to decrease (buck) voltage. The use of stabilizers allows you to create a UPS circuit that can withstand long, deep “sags” and “sags” of the input mains voltage (one of the most common problems in domestic power grids) without switching to rechargeable batteries, which can significantly increase the “life” of the battery.

Inverter

Inverter- a device that converts the type of voltage from constant to alternating (similarly, alternating to direct). Main types of inverters:

• inverters that generate rectangular voltage;
• inverters with step-by-step approximation;
• inverter with pulse width modulation (PWM).
• converter with pulse-density modulation (PDM, English Pulse-density modulation)

An indicator that characterizes the degree to which the voltage or current shape differs from the ideal sinusoidal shape - nonlinear distortion coefficient (English). Typical values:

• 0% - the signal shape is completely sinusoidal;
• about 3% - a shape close to sinusoidal;
• about 5% - the signal shape is close to sinusoidal;
• up to 21% - the signal has a trapezoidal or stepped shape (modified sine or meander);
• 43% and above - a rectangular signal (meander).

To reduce the influence on the voltage form in the supply network (if the input node of a UPS built according to a double conversion circuit is a thyristor rectifier, a nonlinear element that consumes a large pulse current, such a UPS causes the appearance of higher-order harmonics), a special one is installed in the UPS input circuit THD filter. When using transistor rectifiers, the nonlinear distortion factor (in English) Total Harmonic Distortion, THD) is about 3%, and no filters are used.

Transformer

Galvanic isolation between the input and output (as a rule, in a UPS this is not done at all for fundamental reasons of passing a “through zero” to the load, that is, the absence of any switching of the neutral wire from the UPS input to its output) is carried out by the UPS installed in the input circuit (between the electrical network and rectifier) input isolation transformer. Accordingly, in the output circuit of the UPS between the converter and the load there is a output isolation transformer, which provides galvanic isolation between the input from the UPS circuit and the output to the connected load.

Interface

For advanced monitoring of the state of the UPS itself (for example, battery charge level, output electric current parameters), various interfaces are used: for connecting to a computer - a serial (COM) port or USB, while the UPS manufacturer supplies proprietary software that allows, after analyzing the situation , determine the operating time and give the operator the opportunity to safely turn off the computer, ending all programs. To monitor the status of uninterruptible power supplies and other equipment via a local area network, the SNMP protocol and specialized software are used.

In order to increase the reliability of the entire system as a whole, redundancy is used - a scheme that consists of two or more UPSs.

Manufacturers

Distribution of UPS sales by manufacturer (2017, IT Research).

Operating modes of uninterruptible power supplies with double voltage conversion

The On-Line UPS has two main operating modes:

A) Network mode(or Online mode).
The UPS operates in this mode when the input mains is within the permissible range (input range - see UPS technical data). In this mode, the load is powered according to the “Input network -> Rectifier -> Inverter -> Load” scheme. Wherein Charger works, the batteries are charging.

B) Battery (standalone) mode(or Onbattery / Battery Mode).
The UPS goes into stand-alone mode if the input mains voltage is outside the permissible range (input range - see UPS technical data). The load is powered according to the “Battery -> Inverter -> Load” scheme. The charger does not work, the batteries are discharged.

Transitions between modes A) and B) are carried out without interruption of the output voltage (switching time is zero). There are no transient processes.

Comment: In technical specifications, the input range is usually designated as “UPS input range without switching to batteries” or “permissible range of input voltage changes (without switching to batteries).”

It is recommended to initially turn on the UPS when the network is normal, i.e. The UPS starts operating in network mode. It is also possible to start without a network (“cold” start or battery start), but you must be sure that the battery is normal. It is recommended not to overload the UPS as most loads are not stable. The recommended maximum UPS load is 75%. It is also necessary to ensure that the starting load currents (if any) do not exceed the rated output power of the UPS.

Attention! Operating the UPS without a battery is prohibited, except when replacing the battery pack.

In addition to the two main operating modes, the UPS has two service bypass modes:

They may also be called emergency mode or maintenance mode.

May also be called "sleep" or "standby" mode.

The UPS enters this mode if the input mains voltage is lost and the UPS has worked for the required time in battery mode, the batteries have been discharged to the set minimum threshold (battery energy is exhausted) and the load has been de-energized. Now the device operates in network standby mode - all power units in it are turned off, only the control board, central processing unit (CPU), screen are working, the CPU is waiting for the input voltage to appear.

There are two options:

• If the network appears within a few hours (or several days depending on the battery type) while the UPS is in network standby mode, the UPS will fully start and go into normal network operating mode (A).
• If the network does not appear for a long time (the time threshold depends on the type of battery), the UPS will turn off completely.

Attention: also see Appendix 1 to this article “Logic of discharge, auto-shutdown after discharge, switching on when the input network is restored.”

Comment: Some UPSs with the “full autostart” function activated do not have a standby (input) network mode, that is, after the input network is lost and the allotted time has been spent in battery mode, the UPS is completely turned off.

On-Line UPSs have emergency mode:

G) Emergency operation.
The UPS switches to it when any internal sensor sends an alarm signal to the CPU, for example, temperature is too high, or the inverter output voltage is too high. In this case, the corresponding power emergency unit is switched off and an audible and/or light alarm is sounded. If necessary, the load is switched to power via the bypass line.

Also, the emergency mode or alarm may be activated briefly during the start/self-test process, this is normal.

Attention: In many UPS models, emergency sound and light alarms are given as follows: the red LED (Fault) lights up and a constant sound signal is emitted.

Attention: if the emergency event is not significant, for example, a slight overload (or temperature rise), then when the source of the problem is eliminated, for example, reducing the load (or room temperature), the UPS will automatically return to operating mode. But, in the event of a serious accident (for example, there was a large overload, while the UPS itself was not damaged), the unit may become blocked and to return it to operating mode, it is necessary to completely restart the device and turn it off.

On-Line UPSs have the following start modes:

H) Start mode
This is a transient (short-term) mode in which the UPS or uninterruptible power supply unit is in the process of transitioning from an off state to a fully on state.

Possible starting options:

1. "Cold" start. The UPS is turned off. There is no input network. We manually start the inverter. The UPS enters normal battery mode.
2. Start from the network. The UPS is turned off. Voltage is supplied to the UPS input (input network is normal). The UPS switches to battery charging mode with the inverter turned off (mode E).
3. Inverter start. The UPS is in battery charging mode with the inverter turned off (mode E). The network is normal. We manually start the inverter. The UPS goes into normal Online mode (A).
4. Autostart when the network is restored. The UPS is in input standby mode (F). The network has appeared. The UPS goes into normal Online mode (A).
5. Full autostart from the network. The UPS is turned off. Voltage is supplied to the UPS input (input network is normal). The UPS goes into normal Online mode (A) if the full autostart function is available.
6. Start according to the program.
7. And others

Attention! In start mode, when the mains is available, most UPSs temporarily activate the bypass (the load is powered through the electronic bypass). This is the typical default behavior of most UPS models. However, if the electronic bypass blocking function is activated when the inverter is turned off (see below), the bypass will not turn on even in start mode!

Attention! If the input network is normal, then after the UPS exits the start mode, two options are possible:

1. The UPS goes into battery charging mode with the inverter (E) turned off, while most UPSs operate in electronic bypass mode (this is how most UPSs behave by default). But if the electronic bypass blocking function is activated when the inverter is turned off (see below), then the bypass will not turn on, the load is de-energized! In any case, now to fully start the UPS you need to start the inverter using the buttons. This is how most UPSs behave by default.
2. If the UPS has the full autostart function activated when mains is present (see below), then after exiting the start mode, the UPS automatically starts the inverter and the UPS automatically fully starts and goes into mains operating mode (A).

Comment: The UPS usually performs a self-test in this mode (see Mode I).

Comment: Some UPSs perform a battery test in this mode (see mode J).

On-Line UPSs have a self-test mode:

I) Self-test mode.
In this mode, the CPU checks all internal units of the UPS, and if a fault is detected, a corresponding alarm is given. In most UPSs, the mode is activated during the UPS startup process. Often testing the UPS and battery is combined.

On-Line UPSs have a battery testing mode:

J Battery testing mode.
In this mode, the rectifier is turned off, that is, the UPS is forced into battery mode, the load is powered by batteries, the CPU draws a conclusion from the battery discharge curve that the battery is serviceable, and if necessary, an emergency indication is given about faulty or replacement batteries.

Comment: In many UPSs, if the test is successful, no messages are issued; if the test is negative, the corresponding signals are issued, for example, an audible signal, an orange “weak battery” LED or a similar message on the screen, a crossed-out battery sign lights up, etc.

Comment: The mode can be forcibly activated manually using buttons, using software, or using a special internal CPU program.

Comment: Some UPS systems may include periodic battery testing.

Comment: in some UPSs, the test mode is activated during the startup of the UPS or its inverter, and if the test fails, for example, the batteries are depleted or not connected, then the UPS does not start.

Appendix I

1. Logic of operation

1.1 Logic of discharge, auto-shutdown after discharge, switching on when the input network is restored

Network OK

• UPS with a power of 1000 VA / 700 W (with 9-12 Ah battery) is turned on manually.

• Load connected. The UPS operates at 50% load (350W) in network mode. The UPS has an estimated autonomy time of 30 minutes.
• Batteries are charging. The floating charge voltage for one 12V battery (float charge voltage) is ~ 13.6 ... 13.8 V (less often, for some models 13.8 ... 14.2 V).
• The network disappeared, the UPS switched to battery mode.
• The UPS normally powers the load in battery mode for 30 minutes.
• After 30 minutes, the UPS output turns off (the batteries are discharged, the load is de-energized). This occurs when the voltage on each 12-volt battery has reached 10 V. This is the end-of-discharge rating for most lead-acid AGM sealed batteries. But the UPS itself continues to work, the logic board, CPU, and screen work. This mode can be called network standby mode (F).
• At the moment the load is turned off, the battery voltage increases to 11-12 V per battery, since the discharge power has sharply decreased from ~ 360 W to about 10 W (1-3 kVA UPS logic boards consume 5-15 W), so the UPS has the ability for a long time work.
• The UPS can remain in this network standby mode (F) from several hours to several days, depending on the number and capacity of the battery.

• • If the input mains appears while the UPS is in mains standby mode, the UPS will automatically fully return to normal mains mode.

Comment: The UPS may not activate the inverter immediately, but after a while, when the batteries are sufficiently charged. This corresponds to the program embedded in the CPU - the UPS should not be turned on completely until the battery is charged and until at least a minimum autonomy time is guaranteed. This algorithm protects the UPS from cases of short-term appearance and disappearance of mains voltage, etc.

• • If there is no input network, then the UPS will remain in this standby mode (from several hours to several days depending on the number and capacity of the battery) until the voltage on each 12-volt battery drops to 10 V (in some UPS up to 7-9 V per battery). Once this threshold is reached, the UPS will shut down completely.

• The UPS is in the off state.

• Now, if the network appears, the UPS will turn on completely on its own (even with heavily discharged/faulty/missing batteries) only if the autostart function is available (this is an option, see below). Most UPSs do not have this function by default, then the UPS can only be started completely manually. At the same time, most UPSs will start normally even with severely discharged / faulty batteries. However, there are device models with a battery test at startup, which will not start if the battery is faulty / discharged below normal / missing. Typically, batteries can be severely discharged if the mains fails, the UPS runs out of battery life, then shuts down and is left disconnected (without mains input!) for several weeks/months.

Comment: The numbers above are approximate // other values ​​are possible

1.2 Operating logic depending on the frequency of the input network. Input, output frequency

Similar to the permissible input voltage range, the UPS also has a permissible input frequency range:

• The UPS operates in Online mode (A) when the input frequency is within the permissible range (see UPS technical data).
• The UPS enters battery mode (B) if the input mains is outside the permissible frequency range (see specifications UPS).

In battery mode, in the absence of an input network, the voltage frequency at the UPS output is highly stable (quartz stabilization) due to the lack of synchronization with the network. Typical frequency accuracy is for different types UPS ranges from 50Hz +/-0.05% to 50Hz +/-0.5%.

In mains mode (A), the UPS output voltage is synchronized with the input voltage mains voltage, that is, if the frequency of the input network is within the permissible range, then the output frequency is equal to the input frequency. Synchronization (equality of phases and frequencies) is necessary for a safe transition between inverter and bypass modes.

Example 1: Input frequency range for 2kVA: 50Hz ±4Hz. Input frequency 52 Hz. The output of the UPS is 52 Hz. The UPS is operating in mains mode (A).

Example 2: Input frequency range for 2kVA: 50Hz ±4Hz. Input frequency 55 Hz. At the UPS output we have 50 ±0.25 Hz. The UPS is operating in battery mode (B).

Comment: Sometimes problems with frequency (when synchronizing the UPS with the network) occur when powering the UPS of various diesel generators. Make sure that the generator power is selected correctly and that its frequency and voltage are correct. Contact the service center.

Note: For some UPSs, the permissible input frequency range can be changed upon request.

2 Additional features

2.1 Function 1: block electronic bypass when inverter is off

Function 1: disabled bypassline when UPS is started with input power

While the inverter is not running, the electronic bypass is turned off. The bypass is also turned off during the start and testing process.

Initially, the UPS is completely disabled. We connect the UPS to the network. The inverter is always off! The load continues to be de-energized until we start the inverter (or it starts automatically).

There is a dangerous presence in the input network high voltage 247 Volts, which is too high. If the bypass turns on when the UPS is turned on (in start-up mode, testing mode, in battery charging mode with the inverter turned off), this can damage the load, so a bypass blocking mode is needed to protect it.

Attention!

Attention! Even if this blocking function is activated, the bypass will still turn on in case of overload, emergency, etc. If this is unacceptable, then the bypass line can be disconnected completely from the network, but the user must understand that by doing so he will sharply reduce the safety of the system.

Comment: in some UPS this function can be activated independently (for example: Pro-Vision Black M).

Comment: On some UPSs this function can be activated upon request.

2.2 Function 2: complete automatic switching on(autostart) if there is a network

Function 2: complete autostart of UPS when mains ok

Initially, the UPS is completely disabled. We connect the UPS to the network. The UPS starts completely automatically by itself. To fully start the UPS, you do not need to press any buttons.

Example when this function is needed:
The UPSs are located at remote GSM base stations, so it is impossible to turn on the UPS manually after they are completely turned off (after a long period of no network), so autostart is needed.

Attention! Most UPS systems have this feature disabled by default.

Comment: In some UPS the function can be activated on request, for example in 1-3 kVA LT.

Comment: in some UPSs this function is activated by default (Smart-Vision S, Power-Vision older versions).

2.3 Electronic bypass range setting function

The electronic bypass line can only be activated (eg due to overload) if the input mains voltage is within a certain range (see UPS technical specifications). For example: 220 V ±10%.

Attention: do not confuse this range of the bypass line with the input range of the UPS without switching to the battery (see above).

Attention: The bypass input voltage range is usually small. This is due to the fact that during the transition the bypass<->inverter load must be reconnected from 220 V (inverter) to the bypass line 220 V ±10%.

If the bypass input voltage range were wider, the following problems could arise:

• Switching the load from a 220 V line to a 150 V line causes a dangerous surge current.
• Powering the load with a voltage of, for example, 140 V is impractical or even dangerous.

Attention: On some UPSs this range can be changed. However, it is better not to do this unless necessary! To avoid damage to the UPS.

On-Line UPS in line-interactive mode

Comment: N-Power UPSs are produced by default in Russian and European standard phase voltage 220 V, 230 V (for three-phase models, respectively, linear voltage 380 V, 400 V).

Attention! Do not change the output voltage settings unless absolutely necessary.

2.7 UPS rated/output frequency setting function

The frequency standards are the following values: 50 Hz, 60 Hz.

The ability to change the rated/output frequency is different for each UPS. Please contact our service center for advice. In most cases, changes are only possible at the factory by prior order or at an N-Power service center.

Comment: N-Power UPSs are produced by default in the Russian and European voltage frequency standard of 50 Hz.

On-Line UPS in stabilizer / frequency converter mode

When the bypass (standby) line or synchronization unit is disconnected, many UPSs can operate as converters (for example, 60 Hz -> 50 Hz) or frequency stabilizers. For any questions related to this mode, please contact the N-Power service center.

Appendix II

Customer question regarding 1000 LT:
It is clear that according to your requirements, the UPS cannot be operated without a battery. But, I would like to understand whether the inverter will turn on in the absence of a battery when connected to the network? The same case occurs if the batteries fail, which will lead to the battery being discharged below the permissible level. Whether a full start from the network works without a battery or not, you will have to check it yourself.

Answer:

Yes, for all small UPSs, the factory (development engineers) prohibits long-term operation of the UPS without a battery, i.e. as a voltage stabilizer. It is allowed to operate the UPS without a battery for up to several hours while the batteries are being replaced. Therefore, if you try to operate the UPS for a long time without a battery, you will lose the warranty. Turning on the inverter, including with bad/missing batteries, is described in this article above.

Cases of faulty or severely discharged (even missing) batteries may be similar / indistinguishable, so the answer to your question “Does full autostart from the network work with faulty / severely discharged / missing batteries in MEV1000LT”: I confirm that, YES (when ordering a UPS with the function full autostart). The exception is severe battery malfunctions as a result of which the charger will not be able to start and enter the “float charge” mode, for example, a crack in the battery and leakage of electrolyte, a short circuit to the case, in this case the UPS will go into emergency mode.

Comment: The “full autostart when network is present” function is disabled in this UPS model in all current deliveries. UPSs with this function enabled are available upon request.

List of double conversion UPS operating modes

OnLine UPS modes:

• A – network mode (or Online mode)
• B – battery (offline) mode (or Onbattery mode)
• C – electronic bypass mode
• D – manual bypass mode
• E – battery charging mode with the inverter turned off
• F – standby mode (input) network
• G – emergency mode
• H – start mode
• I – self-test mode
• J – battery testing mode

Appendix I:

1 Operating logic

1.1 Logic of discharge, auto-shutdown after discharge, switching on when the input network is restored

1.2 Operating logic depending on input frequency. networks. Input, output frequency.

2 Additional features:

2.1 Function 1: Electronic bypass interlocks when the inverter is off

2.2 Function 2: full auto-on (autostart) when there is a network

2.3 Electronic bypass range setting function

2.4 Possibility (function) of operating On-Line UPS in line-interactive mode

2.5 Mode (function) GreenMode

2.6 UPS rated/output voltage setting function

2.7 UPS rated/output frequency setting function

2.8 Possibility (function) of operating On-Line UPS in stabilizer / frequency converter mode

in case of an accident, maintenance and other necessities.
The transition to manual bypass is carried out in accordance with UPS instructions (usually the inverter must be turned off first and the UPS is transferred to electronic bypass) otherwise it may be accident.

An uninterruptible power supply is a component of the power system that is located between the load and the supply network. The main function of a UPS is to provide uninterruptible power. How does an uninterruptible power supply work? A simplified UPS circuit includes batteries and special UPS elements that compensate for disturbances in the main network, namely an inverter, a rectifier, a filter, and in some cases. Today, uninterruptible power supply systems are divided into three groups. Each group has its own operating principle of the UPS.

The key components of UPS are. It is the batteries that determine how long the UPS operates when the power is turned off. As a rule, UPSs use lead-acid batteries with the following parameters: voltage 12V and capacity 7Ah or 9Ah. The batteries are of the sealed and maintenance-free type. The simplest UPS uses 1 battery, but in powerful uninterruptible power supplies their number can be many times larger.

Backup UPS

The so-called backup UPSs are the simplest and most affordable. The principle of operation of an uninterruptible power supply of this type is extremely simple: the load is powered through the network if there is voltage there, otherwise the power is switched from the battery. The battery is charged while the UPS is operating. According to statistics, the efficiency of such UPSs during power failures is 55-60%.

In most cases, you can talk about how a UPS for a computer works by referring to the operating principle. Most home UPS systems for computers are made using this technology. The level of protection that they can provide is the lowest of all existing uninterruptible power supplies. The signal is filtered only partially. Often, this level of protection is quite sufficient for home appliances, since the quality of power in such networks is slightly higher than in industrial ones.

Backup UPSs work great in tandem with a computer, but they are absolutely not compatible for working in tandem with pumps, heating boilers and other similar equipment, since the operation The backup UPS does not provide a sinusoidal voltage waveform. For computers this is not critical, since they use switched power supplies. This fact allows such devices to withstand a small power failure due to the presence of a certain amount of energy in their own capacitors. The offline switching time from the network to the battery ranges from 2 to 15 milliseconds. The UPS operation circuit includes an inverter that turns D.C. Battery to AC. It should be noted that such UPSs are usually low-power.

Line-interactive UPS

The design and operation of interactive uninterruptible power supplies is almost identical to backup UPS. The exception is the ability to stabilize voltage, which is carried out using a switching device. The advantage of stabilization is that there is no need to switch the power supply in case of significant voltage deviations. Input voltage deviations can reach about 20% of the normal value. The output voltage of the uninterruptible power supply practically does not fluctuate. The protection efficiency of line-interactive UPSs is 85%.

Compared to backup UPSs, they provide a higher level of protection, but are inferior. The operation of a linear-interactive uninterruptible power supply can be divided into two groups. Devices belonging to the first group produce an approximate sinusoid at the output, that is, a stepped one. The second group produces a “pure” sine wave without any distortion. The latter in some cases can become a replacement for an online UPS. The presence of a pure sinusoid at the output allows them to be used to protect electric motors and heating boilers.

Online UPS

The most reliable and high-tech UPSs are of the online type. They implement double conversion technology - the most advanced of all existing ones. The degree of protection provided by such devices tends to 100%, regardless of which operating modes of the UPS are active: from the network or from the battery.

How does a UPS with online topology work? In fact, the principle of operation is embedded in the name itself. The input current is converted to DC by the rectifier, after which the inverter converts it back to AC. Alternating current The output has ideal parameters both in voltage form and in its value. The UPS contains a backup line - bypass, through which power is supplied in the event of a malfunction of any of the nodes of the uninterruptible power supply.

It is commonly said that the switching time to the battery is zero, but in reality the batteries are always connected to the circuit. That's why UPS data is called online. Such an uninterruptible power supply device allows you to protect the load from any types of disturbances that may occur in the backbone network.

Such UPSs are used to protect critical and very sensitive loads. All powerful UPSs are made using this technology. Despite the high power, additional solutions are used that allow increasing autonomy. Most often, the design allows the UPS to be used in conjunction with a generator or with external batteries.

However, double conversion also has its disadvantages. The UPS device is quite complex, which does not have the best effect on its cost. The presence of double conversion reduces the efficiency, but on modern UPSs it is quite high. Special energy saving technologies have been implemented to increase the efficiency useful action up to maximum values. In addition, the double conversion process is accompanied by heat generation and noise. It is worth admitting that specific gravity All these disadvantages are incomparably small in comparison with all the advantages, and most importantly with the level of protection.