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How to connect two power supplies. Parallel connection of several loads to one output (30%, Ohm's law)
Alexey OMELYANCHUK, expert
Innate greed (in other words, thriftiness, housekeeping) does not allow even reasonable designers to design intelligent systems. It would seem that you need to connect 32 “Exit” signs to the system (one on each floor), install the required number of relay blocks - and you will be happy. For example, 8 blocks of 4 relays each. But no, because I want to save money, and therefore the project will have one relay output (fortunately, the relay “holds” 3 amperes), to which all 32 plates will be connected to one pair of wires in a long chain (total consumption, okay, we consider it acceptable - 32 * 90 mA = 2.88 A). The total length is approximately 300 m (10 m between signs). What's the ambush?
The first catch is that most signs (lamps, sirens, sirens and other similar devices) have a very limited operating voltage range. For example, the popular KOP-24 device operates at a voltage from 18 to 28 V. Huge range! Yes? No.
We install a standard 24 V power supply (in fact, it usually outputs 27.5 V, because it contains two lead batteries with a “recharging” voltage of 13.8 V - like in a car). Fits? Fits. Further. The system should operate in case of power failure for another 24 hours in standby mode and 3 hours in alarm mode. It is clear that the batteries are also calculated “economically”, so that by the end of this period the voltage at the output of the power supply will be about 20 V. Is it suitable? Fits too. But! There is a reserve of 2 V left for the voltage drop on the wires.
At a current consumption of 3 amperes permissible resistance wires are only 0.6 ohms. Let us remember one of the first articles about 30% - the resistance of a single wire with a cross-section of 1 mm 2 and a length of 100 m = 2 Ohms. Let's recalculate and get: with a cable length of 300 m, the resistance is 0.6 Ohm for a cable with a cross section of 2x16 mm 2. Such a cable can only be bent over your knee, and you may end up with a bruise. The cost of one (!) meter of such cable is equal to the cost of one scoreboard. Wow savings...
And it won’t be possible to connect such a cable to existing boards, and it won’t even be easy to stretch it through existing risers between floors.
And here we draw attention to the fact that there are plates with a noticeably wider range of supply voltage, and at the same time with a significantly reduced current consumption. This effect is usually achieved using pulse sources nutrition, but I will not go into the technological secrets of the manufacturers. For us now it is important that there are seemingly not very different devices with an acceptable supply voltage range of 10-40 V and a current consumption of 20 mA. Let's count everything again. We will leave the power supply the same, usual for 24 V fire systems. The permissible voltage drop even from completely discharged batteries will already be 20 V-10 V = 10 V. The current consumption of the entire chain is 32 x 20 = 640 mA. We divide and we get: we are satisfied with a resistance of 16 Ohms. This means a 2 x 0.75 cable is suitable! It's a completely different matter! (Fig. 1).
Now let's calculate a little more accurately. The average current in the cable is not 640 mA at all. It is only in the first section from the relay to the first display that the current is maximum, and then the current is less. If we assume that the displays are distributed evenly along the loop, then the average current can be considered equal to exactly half of the full current, i.e. 320 mA. Mathematics enthusiasts can figure out for themselves why this can be considered, I will explain to others: in the first section the current flows from 32 boards, in the next - from 31, etc. Accordingly, the voltage drop in the first section is equal to R cable * 32 *! board, on the next R cable * 32 *! board, etc. Well, the sum of the series 32 + 31 + ... + 2 + 1 is known to be approximately 32 * 32/2. In total, to a first approximation (with an accuracy of 30%), we can assume that an “average” current equal to half the full current simply flows through the cable. It became even easier. You can choose a cable of only 2 x 0.35, which is just a penny, even in a fire-resistant version.
Now let's move on to the sad stuff. Standards (and common sense) require monitoring the integrity of the communication line from the device (relay unit) to the siren. Indeed, you personally check the wires from the switch to the light bulb several times a day, but a fire alarm can stand for years and never turn on the sirens. And only in the event of a fire, when it is too late to repair the wiring, should it work. So, control.
Of course, all manufacturers offer, along with conventional relay blocks, similar blocks with a communication line monitoring function.
Basically, there are three different technologies. The first is periodic measurement of the direct resistance of the line. It does not require any additional devices, monitors not only the entire line, but also the sirens themselves and generates an alarm if there is a significant change in the line resistance. The disadvantages of this approach are that it only works well if there is only one siren on the line. Well, two or three. And if there are 32 of them, then it is impossible to notice the disconnection of one of them. Therefore, this method is not suitable for lovers of austerity. In general, such a solution can only be applied in the case of an addressable system, when the “relay unit” is actually a rather small and cheap device. And, by the way, in this case it often turns out that at the time of testing the siren “works a little.” Although very little current is applied to it, this current can be enough to make a modern electronic siren "tick" just a little. Yes, the siren will not give out its 110 dB and will not alarm the entire village, but if it is located in the security room, the every minute “ticking” is quite annoying. While we're on the subject, I'll mention the solution to the problem. You need to connect a small resistor with a resistance of approximately 1-5 kOhm in parallel to the siren. The entire test current will go into this resistor (usually no more than 1 mA), the siren will not move at all. And in operating mode, when 12 V is supplied, an acceptably small “extra” current will flow into the resistor - a couple of milliamps.
The second technical solution is to place a special device at the end of the line, a digital or analogue “responder”, with which the control unit constantly “communicates” and checks for communication. The solution is very effective, although, it must be said, it allows you to control only the “communication line” (literally, as required by current regulations). Actually, the connection terminals for the sirens and the sirens themselves are not controlled in any way. Well, the last drawback is the noticeable price of the devices. This solution makes sense only if you intend to connect really many sirens (signs) to one line.
The third solution, very common (especially 10-20 years ago) is to use a diode as a termination load and check the loop by applying reverse voltage. The idea is that the sirens will not work due to reverse voltage, and the diode will allow current to pass through, this is a test for an open circuit. Moreover, the voltage drop across the diode - 0.6 V - can be easily detected and made sure that there is no short circuit on the line either. Alas, everything is not simple. Firstly, many alarms have a protective diode at the input, which protects them from both reverse polarity and overvoltage (this is precisely a protective diode - essentially a zener diode). (Fig. 2)
What happened? Each siren has the same diode as at the end of the line - our relay unit will not notice if the cable breaks somewhere in the middle. The result is that manufacturers of such units (with such control technology) recommend installing an additional “straight polarity” diode for each siren. At the same time, such a diode will protect the siren from damage by the test current if the siren does not have built-in protection (alas, the race for cheapness is typical not only for the hero of Pushkin’s fairy tale and our supposed designer, but also for siren manufacturers). Well, okay, let’s say one more diode, it’s inexpensive, especially since respected manufacturers offer a ready-made unit with a pair of diodes and terminals (or protruding wires) for ease of installation for a modest price. If you are building a fire protection system, the solution is quite good. The integrity of the communication line is, of course, controlled, and the standards are met. The only trouble is that additional devices and a couple of connections (or even twists) have appeared between the communication line and each siren, which, of course, does not add reliability to the system.
In conclusion, let’s look at another example of extreme greed (and at the same time amazing technical beauty) that I recently encountered in design decisions. Given: there is a fire extinguishing start-up unit that produces 3 amperes output. A very good unit, with a pulse stabilizer, i.e. it produces exactly the guaranteed current - 3 amperes, regardless of the load. It also gives out 3 amperes for a short circuit and gives out 3 amperes for a load of 1 Ohm (it turns out only 3 volts at the load - who remembers Ohm’s law). The designer's desire was to launch approximately 100 Buran-type modules from this block, each requiring 100 mA. In principle, connecting several squibs (fuses in Burans, strictly speaking, are not squibs, but for simplicity I will call them that) in parallel to the output of one launch unit is a completely acceptable solution according to existing standards. Yes, it is impossible to control the connection circuits of each squib and the squibs themselves - only the notorious integrity of the communication line, but according to the standards this is allowed. I note, by the way, that in no car is the communication line with the airbags ever monitored - it is the integrity of the airbag squibs themselves that is monitored, each individually - but we are talking about us, our loved ones, portraying Schumacher on a slippery road, and not about some then there is an unlikely fire in a building, which we may never see after design. (Fig. 3)
So, several squibs are parallel, resistors are connected to them in series, so that in the event of a short circuit in the squib, it does not short-circuit the entire line and does not interfere with the operation of the remaining squibs (usually, when triggered, the squibs go into a “break”, but there are different cases. Although more often a short circuit is formed simply by itself, over time, due to metal corrosion and chemical processes in the squib filler). The idea is simple: even if the source current is distributed unevenly after switching on, the first to burn out will be those squibs that received more than average current, after which the current will be redistributed among the remaining ones and the next one will work - and all this within a few milliseconds after the output is switched on. An essential condition is that the output current of the control module must be sufficiently sufficient for all squibs. It should not happen that the current, due to various differences on the wires and contacts, at the first moment after switching on, is distributed equally “a little bit to everyone”, so that there is not enough for everyone to trigger. Typically, manufacturers recommend one and a half times the margin for such inclusion. In the case of Burans with a starting current of 100 mA, this means that a module with an output current of 3 A can be connected to 20 Burans.
So, back to the manifestation of healthy greed. I would like to set fire to 100 Burans with one module (in fact, “only” 75). There won’t be enough current right away - for 75 Burans you need 7.5 amperes, we only have 3 A, and we need to provide a small reserve. You can, of course, install a couple more simple relays and switch 3 groups of 30 squibs in turn, but greed does not even allow this. However, there is a solution, and a very beautiful one (do not try to repeat it in real life, the described trick is only available to trained stuntmen in helmets and with certificates from a neuropsychiatrist). So. We put different resistors in series with the squibs. We will ensure a deliberately uneven current distribution. We will connect the first group of 15 Burans directly. The second group (also 15 pieces) - through 20 Ohm resistors (the resistance of the squib itself is also 20 Ohms - therefore the total resistance of these branches will be twice as large). Another one - through 60 Ohms, i.e. the resistance of these branches will be four times greater. Etc., there will be 6 groups of Buranov in total, the total resistance in the branch of the first group is 20 Ohms, the second - 40, then 80,160 and finally 320 Ohms. A typical binary ladder. The conductivity of the first group is even less than the sum of the conductivities of the remaining groups. Therefore, at the first moment after switching on, more than half of the total current (i.e., more than 1.5 amperes) will flow into this group. Accordingly, this current is enough to trigger the squibs of the first group. When they fire, they will be “open” (if everything happens as expected) and the output current of the starting module will again be redistributed, so that the next group of 15 squibs will receive more than half of this current. Now they will work, well, etc. A little trouble is that the last group requires a voltage of 32 V to work, so we had to design the module’s power supply from 3 power supplies of 12 volts each - a total of 36 volts. (Fig. 4)
Theoretically it should work. In practice, it is enough for one squib to work “shortly” or at least simply not to work, and most likely not a single squib in the following groups will work. I'm not even talking about the reliability of monitoring the integrity of such a complex structure. Well, of course, this, in principle, does not work with every starting module, but only with one that provides (limites) a fixed current. If the module has a regular relay, and the module tries to output all 36 volts at once, then the current in the squibs of the last group will immediately be 100 mA, in the penultimate group - 200 mA at once, etc., so that the total current will exceed 40 ampere, of course, the power supply protection will work earlier than the squibs, and not a single Buran will start at all.
What do I want to say to all of this? Greed is limitless. I do not advise anyone to ever connect more than one load to one output. Parallel connection For several consumers, this is already greed, leading to a decrease in reliability, even if this is done within reasonable limits (I repeat, I cited the method of launching 75 squibs from one output only as an illustration of the application of Ohm’s law, as an exercise for the mind). When control modules cost more than the potential damage from a fire, this was still understandable. But now, when electronics are becoming cheaper every year, according to Moore’s law, the right decision is either to use modules with a large number of outputs (and connect one consumer to each output), or to use miniature modules directly near each consumer. The second option will not significantly increase the cost of the entire system (the cable structure is the same), but it can significantly improve the quality of monitoring the integrity of all lines, all connections and the performance of all devices (to the extent that it is possible to check the performance of the squib without igniting it). However, it is inappropriate to talk about specific solutions of this class in a generally useful information article - this would be direct advertising, so read about specific products in my other articles.
It is generally accepted that of all the technical means of OPS, power supplies (PS) are the simplest product. In most descriptions and characteristics of IP, manufacturers indicate a set of standard parameters without specifying how to implement them. But since the truth is always hidden in the nuances, without understanding the meaning and methods of implementing the given indicators, it is impossible to assess the quality and capabilities of products. The easiest way is to evaluate each IP parameter according to its purpose and technical methods of implementation.
Overload and short circuit protection. ( Note: Here and below, the authors do not classify all types of protection on fusible links and self-resetting fuses as protection, considering them decorative elements of the IP circuit.) One of the most complex indicators. Overload protection is protection against load current exceeding a safe value designed for long-term operation; short circuit protection is against critical currents that can instantly damage the source. Typically, short circuit protection is “fast” and is set to a sufficiently high high current(to prevent tripping when a capacitive load is connected), the overload protection is “slow” and is set to a current corresponding to the maximum permissible long-term current.
Let's say the short-circuit protection current of a 3-amp source is set to 8 A, but there is no overload protection. If the consumer unintentionally sets the current to 4 A, then it is obvious that the source will work for some time, but not for very long. Sometimes in starting sources the operating current in the presence of batteries is set higher than when operating without batteries. In this case, work will be carried out until the batteries are discharged.
It should be borne in mind that short circuit is different from short circuit, just like overload is different from overload. For power supplies, especially pulsed ones, the most dangerous is the so-called sparking circuit, against which conventional protection is in most cases powerless. As a rule, if they try to solve a problem, it is solved by blocking the power supply from restarting for some time after detecting a short circuit. If you are interested in such a parameter, it makes sense to check with the developers how it is implemented, or check it from personal experience by creating frequent short circuits on the output.
It is especially useful to check the operation of the source for a capacitive load, since devices used as a load, as a rule, contain storage capacitors. The more such devices, the greater the total load capacity. When voltage is applied from the power source, the uncharged capacitance is perceived by it as a short circuit. The duration of this short circuit is greater, the greater the load capacitance and the higher the resistance of the connecting wires (with an increase in the resistance of the connecting wires, the amplitude of the short circuit current decreases with a simultaneous increase in duration). Thus, a power supply with a rated output current of, say, 3 A may not turn on to a load with an average current consumption of 100 mA, since the moment it is turned on, it will constantly trip short circuit protection.
It is quite easy to check this parameter: connect an electrolytic capacitor with a capacity of 2000 μF to the output of the source (without a battery) according to the polarity and the operating voltage is greater than the output supply voltage of the IP, and connect the source to the network. If the protection works in it, you can safely scrap it.
Note: Let us explain why a capacitive load at the moment of switching on is perceived as a short circuit. It is known that the capacitance charge current is described by the expression: Ic = C (Uc/ t), where C is the load capacitance in Farads, (Uc/ t) is the rate of change of voltage across the capacitance (V/s). Let a 24 V source be turned on to a capacitive load of 1000 μF and the source turn-on time is 1 ms. Let us assume that the internal resistance of the source and the resistance of the connecting wires to the load are equal to 0. Then the peak current of the source per charge of the load capacitance is:
Ic = 1000-6* (24/10 -3) = 24 A.
The concept of protection has another important and particularly significant aspect: the ability to power a device that has several outputs or several devices, each of which has outputs. Imagine the circuit shown in Figure 1.
Rice. 1
Let a short circuit occur in a device protected at the output by a fuse link or a self-resetting fuse. If the protection in the IP operates before the fuse, the entire device(s) will be de-energized and, accordingly, the existing alarm conditions will be reset. Next, the source will try to turn on, and the process will repeat accordingly. As a result, the entire system will be inoperable.
The significance of this indicator is perhaps the most significant of all. We recommend checking it after installing the system by short-circuiting any output of the device powered by it. Thus, another parameter is secretly added to the protection against short circuits and overloads - the ability of the source to disable the safety elements of the outputs of the devices it feeds without de-energizing these devices and damaging itself (critical overload withstand time). If such a function is available in the sources, then it is implemented only if there is a battery, otherwise the power of the source itself may not be enough to disable the safety elements.
Operation of sources in parallel
Essential parameter. It assumes that the sources have a current (power) limitation, i.e. as the output current increases, the output voltage is reduced so that the current does not exceed a safe value. Imagine that this function does not exist and two sources are connected in parallel, one with a voltage of 13 V, the other with 13.6 V, and the resistance of the wires between them is 0.1 Ohm. Then a current of 60 A will flow from one source to another, which will lead to the failure of one source or the activation of overload protection in it.
Redundant power supplies mean sources that operate both from the network and from batteries in the absence of a network, as well as those that have the ability to additionally feed the network output with battery current (in the latter case, they are also called starting power supplies). An important feature of such power supplies is the switching circuit from the network source to the battery and back, as well as additional feeding of the network output with battery current. There are two main methods: switching to a battery, or a current-limiting circuit. Let's consider the first option. The most disgusting thing that can happen is a circuit that switches to the battery and back via a relay (Fig. 2a).
Let's assume that at some point in time there is an overcurrent of the mains source and the relay switches to the battery. Not only is the load completely de-energized at the moment the relay contacts are switched, but after they are switched, the current from the network source stops, the protection is turned off, and the relay contacts return back. Then the process is repeated. The more common is the diode switching circuit (Fig. 2b).
Rice. 2
Its undoubted advantage is the constant power supply to the load, but it has many disadvantages. If the mains source and battery have different voltages, then switching from the source to the battery and back, as in the previous case, will lead to voltage surges between the level of the network source and the battery, especially noticeable in warning systems when protection is triggered for peak load currents. This is usually heard in loudspeakers as characteristic clicks. The output diodes have to dissipate significant power, which aggravates the cooling problem (at a current of 10 A, the loss is about 10 W), in addition, the additional volt drop across the pass diode reduces battery life.
There are also hybrid versions of both methods, in which the relay contacts are shunted by diodes (the diodes work during switching, and the relay contacts work after switching). The fatal problem with this method is the voltage surges noted above.
And, of course, for starting power supplies, you need to keep in mind that the overload protection current when operating from the mains and batteries must be different (otherwise the very concept of a starting unit loses its meaning). In any case, a feature of all switching circuits is the underutilization of the mains source current when switching to the battery and, accordingly, shorter operating time during overloads.
An alternative, but more expensive, source circuit is a current limiting circuit. Its meaning is that as the load current increases beyond the permissible limit, the output voltage of the source begins to decrease and with a further increase in the current it is compared with the voltage on the battery. In this case, the load current is distributed between the battery and the source in proportion to the voltage reduction slope line (Fig. 3). Note: This is the same method that allows sources to work in parallel.
Rice. 3
Let's consider the operation of the circuit step by step. Let's assume that the battery is not fully charged and the voltage of the mains source and the battery are different. As the load current increases and it reaches the start limiting current, the output voltage of the SM begins to decrease. Let the output current be set at the level of point “B”, then the output voltage will correspond to the voltage on the battery, and the load current will be distributed between the current of the network source and the battery.
As the batteries discharge, the voltage of the source and battery will decrease with the redistribution of currents between them. It is obvious that at the entire stage of reduction, the current of the network source should not exceed values that are safe for it, and the power supply circuit must recognize the fact of operation from the battery in order to set the overload protection current at a higher level.
The starting block circuit based on current limiting does not have the disadvantages of switching circuits and, importantly, allows the operation of several power sources in parallel.
Battery charging method
Traditionally, there are two main charging methods: buffer and accelerated. Each of them has its own advantages and disadvantages. It is clear that the accelerated method provides faster charging; its technology is that the battery is charged DC(about 0.1 C) to a voltage of approximately 14.2 V, then the current is reduced and the voltage is maintained at 13.6 V. The disadvantages of the method include the complexity of the circuit implementation, as well as the leveling of the main advantage (accelerated charge) when installing a larger battery capacity (when installing a battery with a smaller rated capacity, the charge current will exceed the permissible one). In the simplest and most common systems, the principle of a buffer charge is used, when the battery is connected to the output voltage source of the power supply through a current-limiting circuit (linear or pulsed, including current limiters) (Fig. 4a).
Rice. 4
During the charging process, as the voltage on the battery increases, the current decreases and the charging process increases in time (Fig. 4b). As a rule, if the technical parameters of the power supply indicate the “maximum” charge current, we are talking about a buffer charge, and the indicated current corresponds to the full discharge voltage. Obviously, such information does not allow you to independently calculate the time to fully charge the battery.
The function is far from superfluous, especially in starting power supplies, where the requirements for battery health are higher than in simple uninterruptible power supplies. Unfortunately, there is no “legalized” metrological method that provides accelerated capacity testing, because this method involves multiple cycles of fully charging and discharging the battery with a calibrated current. In all schemes where capacity control is implemented, the principle of measuring the internal resistance of the battery and comparing the results obtained either with the initial values or with a certain limit level is used, after which further operation of the battery is impossible. Those. Capacity is measured very arbitrarily. Schematic diagram control is shown in Figure 5.
Rice. 5
Key K periodically connects the test resistance Rtest to ground. A divider is formed between the internal resistance of the battery Rin and Rtest, which leads to a decrease in the controlled voltage E. The value of Rin is determined by the degree of reduction of this voltage. Based on the resistance analysis, a decision is made to reduce the capacitance. What is important is that the method is identical to the method for accelerated testing of the quality of car batteries.
In fact, this is the variable component of the output DC voltage. In linear sources it is caused by insufficient filtering of the input network voltage, in pulsed sources it is caused by surges when switching power key transistors. Depends on the load current, while in linear sources it increases with increasing load current, and in pulsed sources, as a rule, it decreases. Traditionally measured in peak-to-peak (Figure 6) or double peak-to-peak values. For pulsed sources, a ripple amplitude of 150 mV or a double ripple amplitude of 300 mV is considered acceptable.
Rice. 6
Availability of several independent outputs. The parameter is not explicitly included in the regulatory documents. Sometimes it is in demand for redundant circuits when powering several devices from one power source. However, you should be more careful about the validity of the reservation in each specific case.
In order: Damage to power supply circuits can be in the nature of an open or short circuit. To prevent a break, it is enough to parallel the power wires from one output, and the problem will be solved.
Now about the closure
Situation 1. Let's consider the circuit shown in Figure 7. Let's assume that a short circuit has occurred on one of the load outputs (the most common case). Moreover, if the source cannot ensure the operation of the protection element at the load output, it will turn off the voltage at all its independent outputs, and this will happen for all sources if the power supply system uses several power supplies for one load.
Situation 2. The product uses a circuit that combines the main and backup power lines into one using two diodes (as shown in Figure 7), and the short circuit occurs in one of the lines before the product.
In this case, due to the voltage drop across the changed resistance of the ground line wires, a voltage surge occurs, which is applied to the “-” power wire. In the product, this impulse is perceived as interference, and a very serious one, the amplitude of which is proportional to the resistance of the wires, and the duration is proportional to the speed of operation of the short circuit protection. Further, with the frequency of attempts to turn on the shorted output of the IP, this interference will be repeated. The equivalent circuit of the power circuit after closure is shown in Figure 8.
Situation 3. The product uses a circuit that combines the main and backup power lines into one with four diodes (as shown in Figure 9), and a short circuit occurs in one of the lines before the product. In this case, an interference pulse is not generated on the equipment, however, due to the loss of voltage across a pair of diodes (which is almost 2 V), the operating time from the battery is significantly reduced. Those. if you have a 12-volt product with a minimum supply voltage of 10 V after combining the power lines, the minimum voltage at the output of the power supply when operating from a battery, when the product is still working, will not be 10.5 V, as expected, but all 12 V.T. e. The operating time from the battery is reduced by almost 40%, and this must be taken into account when choosing the battery capacity. The situation with one diode is, of course, easier, but the loss of volts is still noticeable (reduction in operating time by about 25%), especially for products with a supply voltage of 12 V. There are other schemes for combining lines (using relays, field-effect transistors), but, in - firstly, they are much more expensive to implement, and secondly, the designer, in any case, must know the minimum supply voltage of the products after this combination, so as not to make a mistake with the choice of battery capacity.
Rice. 7
Rice. 8
Rice. 9
Rice. 10
Thus, the presence of two independent power lines sometimes not only does not solve, but aggravates the problem.
The power supply system is not limited only to the choice of a power supply with a certain number of independent outputs, but requires an integrated approach taking into account the operating characteristics of the connected equipment.
Efficiency The efficiency is fundamentally different for pulsed and linear sources; for pulsed sources it is, of course, greater. In the group of pulsed sources, a 1-2% difference in efficiency is practically insignificant; the thermal regime of a power supply with a lower efficiency is worse, but if the manufacturer guarantees its operation, you should not pay serious attention to this parameter.
Power factor corrector (PFC). A device that provides an increase in power factor, i.e. reducing the share of the reactive component in power consumption. From the point of view of the electrical network, so to speak, the load in the form of a power supply equipped with a PFC appears to be practically resistive. A power corrector is presented by many as a device that saves energy, but when applied to power supplies it performs more important functions:
- increases the range of supply voltages (as a rule, power supplies equipped with a PFC have a range of input supply voltages from 90 to 250 V);
- facilitates the operation of the power part of the converter and accordingly increases its reliability;
- reduces the level of interference emitted into the electrical network.
Controlled parameters. This refers to a set of parameters automatically controlled and measured by the IP circuit. Monitoring and displaying these parameters is optional, but is significantly useful when setting up and operating complex systems. The controlled and displayed parameters of the IP may include:
- input voltage;
- output voltage;
- output current;
- presence of output overload;
- presence of a short circuit;
- battery voltage;
- specific battery capacity;
- battery charge current;
- charger performance;
- and etc.
Based on these characteristics, you can evaluate the state of the power supply, the performance of the power supply and backup batteries, the presence of breaks and short circuits in the load connection circuits, the serviceability and quality of operation of the equipment connected to the power supply. For example, an increase or decrease in the output current may indicate faulty circuits or connected equipment; monitoring the battery capacity will allow you to replace it in a timely manner. Parameters can be displayed on IP indicators (in full liquid crystal form), adjustment consoles, and system-wide consoles.
In conclusion, I would like to wish everyone involved in the use of IP to be attentive to this type of product. There is no point in having complex systems and expensive equipment if it turns out to be de-energized at the right time.
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