The choice of automatic machines for LED lamps. Useful information. Do LEDs have inrush currents?

Modular circuit breakers are used to protect low-current and signal circuits from overloads and short circuits. They are made one-, two-, three- and four-pole, mounted on DIN rails in electrical panels. In everyday life, they actually play the role of automatic traffic jams.

Selection options for MCBs

The price of modular AB depends on the design, dimensions and technical parameters.

Rated voltage. Depends on the insulation resistance of the housing material.

Rated current. Should be slightly higher than the rated load current. With an excess "reserve" the machine will not work at the time of overload. The calculation is also made taking into account the cross section of the conductors. The thin wire gets hot. If In of the switch is greater than the allowable I for the conductors, they will burn out, but the machine will not knock out.

Breaking capacity. This is the highest short circuit overcurrent at which the circuit breaker opens the circuit and is not destroyed. The higher the indicator, the better, but the prices for "automatic plugs" with a large breaking capacity are quite high.

Time-current response characteristics. Starting currents of equipment under the influence of transients are much higher than the nominal ones. So that the machines do not work with a short-term action of the starting current, they are produced in several types:

B. Only for active load (lamps, electric furnaces, irons);

C. For home and offices (refrigerators, washing machines, computers);

D. For networks with a significant reactive load (powerful electric motors).

Buy modular circuit breakers by affordable price offers you an online store "AVS-electro". On the site you can see the catalog, which indicates the current cost of the goods, and place an order. If you have questions about the assortment or delivery conditions, our managers will promptly answer them by calling the hotline.

Circuit breaker - This is a protective automation device designed to disconnect short-circuit currents and disconnect in case of overcurrent.

Based on this description, we understand that the circuit breaker provides two types of protection, and it is very important to know and understand that the circuit breaker is designed to protect wiring. Think for yourself, in case of a short circuit, current which flows in the wires can reach from 1000A to 10,000 A. And it is clear that with such currents no cable will last long. A cable with a cross section of 2.5 square millimeters, which are often used for residential electrical wiring, will burn like a Bengal fire at such currents. And it is not surprising if this leads to a fire.

Second defense circuit breaker is the overload protection again of the wires.

And again, it is very important to remember that it is the wiring that is being protected. Since when too much load current flows through the wire, exceeding the rated current by at least two or three times, the wire will get very hot, and in the end the insulation may melt and a short circuit will occur. Well, that is, of course, if there is no fire before that.

So we have decided on the importance of using the right circuit breaker, and now I suggest you go directly to the consideration of the criteria for choosing circuit breakers.

Circuit breaker rating selection

At , the first thing you need to pay attention to, and in general, let's say, to know in advance before going to buy, is the rating of the circuit breaker. That is current which will normally flow through this circuit breaker. And when the rated current is exceeded, the machine will turn off.

The current that the circuit breaker will trip must be chosen for reasons of common sense. That is, if, for example, you have an old wiring through which you can pass a current of up to 10A, and the expected load will be, say, about 20A, then you need to choose a circuit breaker from the condition of ensuring the safety of the wiring, that is, choose the machine closest to 10 A.

It also follows from this that periodically you will have to change the wiring, since with an increase in the number of electricity consumers, the load also increases. And over time, the old wiring is simply not able to provide the flow of such a large current.

Wiring - this is exactly the case in which it is appropriate to say: "The miser pays twice." Therefore, if you are replacing electrical wiring, choose a wire cross-section with a margin.

Selecting the class of the circuit breaker.

You may be aware of such a phenomenon as inrush currents.

Starting currents- this is the current that flows at the moment of switching on any consumer of electricity, and this current can exceed the rated current from 3 to 12 times. It is clear that different consumers have their own starting currents.

So, in order for the circuit breaker not to operate on inrush currents, as on short-circuit currents, there is such a thing as a class of a circuit breaker.

The class of the circuit breaker is indicated by a letter next to the number indicating its rated current.

Let's look at what classes there are:

B- withstands starting currents 3-5 times higher than the rated current.

FROM- withstands starting currents 5-10 times higher than the rated current.

D- withstands starting currents 10-12 times higher than the rated current.

So the most commonly used in everyday life are circuit breakers with class B, and C.

Choice of selectivity of the circuit breaker.

Selectivity - this is a property of protective automation to turn off only damaged sections of the electrical circuit. And to ensure this property, it is necessary to correctly choose both the rating and the class of the circuit breaker.

To achieve trip selectivity, the rating of the input switch must exceed the ratings of all automata by groups. And correspond to the maximum allowable load that the supply wire and the wiring of the apartment can withstand.

Circuit breakers of groups are already selected according to the current that will flow through them.

Thus, in the event of a short circuit, say, in one of the outlets, only the circuit breaker of the outlet group will turn off, and not the introductory machine.

Short circuit currents

Same with circuit breaker selection its breaking capacity should also be taken into account. Indeed, at high short-circuit currents, the machine may simply not be able to open the contacts. This phenomenon is also called contact sticking.

Therefore, when choosing a circuit breaker, it is best to choose a machine that can turn off currents up to 3-4.5 thousand amperes. They will cost more, but consider it an investment in your own safety. After all, imagine what happens if your circuit breaker simply cannot, due to circumstances, turn off the short circuit ...

Selecting the manufacturer of the circuit breaker.

As for the choice of manufacturer, many people are often interested in which country it was made in, but this is not quite the right approach, since components are made in different places, and even bought from other manufacturers. Therefore, when choice it is better for the manufacturer to trust the brand, or the advice of the seller, after all, the seller has good purchase statistics, and knows what circuit breakers buy more often, and complain less often.

Not every manufacturer in the catalog indicates starting currents for fixtures.

In the catalog of the SLICK.PRS ECO LED 45 5000K lamp, the starting current is 35 A. The lamp power is 42 W.

Recently on my channel youtube there was a video where I, using an example, told how I would perform task lighting. I was hoping that they would ask me, but what about the starting currents, won't the C6 machine work? For some reason, no one paid attention to this.

The fact is that now I will try to prove to you that for starting currents LED lamps in most cases you can ignore it.

When choosing a circuit breaker, it is important to know not only the operating current, but also the starting current. But, even if you know the starting current, this does not mean that you can choose the right protective device. The duration of the starting current is very important.

Since I did not find the duration of the inrush current in the catalog, I asked the manufacturer a question.

On the same day I received a response:

As you can see, the starting current of this lamp is only 3 μs. In my opinion, the duration of the starting current of all lamps will be approximately the same.

Let's do some math and justify everything with numbers.

Estimated current of 50 fixtures: 0.2*50=10 A.

Starting current of one lamp: 35 A.

Starting current of 50 fixtures: 50*35=1750 A.

Let's choose a circuit breaker with characteristic C16.

The ratio of starting current to the rated current of the circuit breaker: 1750/16=110.

Let's determine how long this inrush current must be in order for the electromagnetic release of the C16 circuit breaker to operate.

I will round up, thus setting the reserve for the strength of our calculation.

From the graph, it can be said that the inrush current should have a duration of approximately 0.005 s or 5 ms. And this is 100 times more (if we count 5 μs) than the duration of the inrush current of our LED lamp.

Now let's check if the machine will work if the current margin is only 20%.

Initial data: 40 fixtures.

Estimated current of one lamp: 0.2 A.

Estimated current of 40 fixtures: 0.2 * 40 = 8 A.

Starting current of one lamp: 35A.

Starting current of 40 fixtures: 35*40=1400 A.

Let's choose a circuit breaker with characteristic C10.

The ratio of starting current to the rated current of the circuit breaker: 1400/10=140.

In principle, the same graph applies to this option: the starting current must be 0.005 s for the machine to work.

Conclusion: when choosing LED lamps, starting currents practically do not affect the choice of the rated current of the circuit breaker, if the characteristic of the circuit breaker is “C”, and the current margin is at least 20%. I advise the stock of the automatic switch for LED lamps to provide 20-40%.

As for the lamps, I think there will still be an article or video on youtube, where I will talk about some of the features and nuances that you need to know about when choosing fixtures.

Over the past five years, LED lights have gone from being exotic gadgets for green lifestyle enthusiasts to everyday items. Therefore, it is not surprising that the installation of such lamps is increasingly carried out not by extra-class engineers within the framework of projects of national importance, but in the most ordinary offices by ordinary electricians or in general by people who have only the most elementary ideas about electricity. And what a disappointment there is when, when you turn on seemingly “economical” LED lamps, a circuit breaker is triggered, which seems to be chosen in compliance with all the rules. Or a paradoxical situation arises when, when replacing fluorescent lamps a fuse is triggered on the LEDs, which previously “held” very “gluttonous” devices of Soviet production without any problems. It's time to lose faith in the cost-effectiveness of LED lamps. Problems arise because the most important parameter of any lamp is not taken into account - the value of the starting current. Moreover, such an approach is imposed by the manufacturers of lamps themselves, often claiming that their products simply do not have inrush currents.

When an electrical device is turned on, as a rule, transient processes are observed. In addition, the device may require more power to start than in steady state. Because of this, a phenomenon such as starting current is observed. The value of the starting current is equal to the maximum value of the input current when the device is turned on. The starting current is expressed either in absolute values ​​or as a multiple maximum value input current to the absorbed current in steady state. Another important value is the duration of the inrush current - the time at start-up during which the input current of the device exceeds the current consumption in steady state.

The presence of starting current is typical even for such an "ancient" and simple light source as an incandescent lamp. A tungsten filament in a cooled state has a resistance 10-15 times less than when it is heated to a temperature when it glows. Accordingly, the starting current of an incandescent lamp is 10-15 times greater than the current consumed in steady state.

That, by the way, is why incandescent lamps (and are similar in principle to halogen lamps) fail most often when turned on.

In discharge light sources, at start-up, energy is spent on creating a plasma between the electrodes, that is, an electric discharge that gives a glow. Such light sources include, for example, sodium, metal halide, and fluorescent lamps. Data on the multiplicity of starting currents and their duration can be found in table 1.

Table 1. Trigger parameters for traditional light sources

The table shows that incandescent lamps and halogen lamps have the highest starting current ratio. But transient processes in them occur faster. The start-up time of discharge lamps, especially HPS and MHL, is much longer, which forces significant current margins to be taken into account when calculating the wiring.

Time-current characteristics of circuit breakers

Modern circuit breakers provide opening of the circuit upon the occurrence of at least one of two events - a prolonged excess of the consumed current I above nominal value I n and short circuit. In the first case, an inertial process of opening bimetallic contacts occurs during heating. Opening occurs under the action of a current of 1.13 I n more than 1 hour or current 1.45 I n less than one hour. In the second case, an electromagnet is instantly activated, opening the contacts. Response time curve tc from the ratio I/I n is called the time-current characteristic.

The existing time-current characteristics are divided into three main groups: AT, FROM and D. Classification is carried out according to the relative value of the current I kz, at which an instantaneous operation of an electromagnetic opening occurs, that is, when the machine detects a short circuit. For group B, the value I kz is from 3 to 5 I n, for FROM- 5 to 10 I n and for D- from 10 to 20 I n. The lower limit corresponds to a response time of 0.1 s, the upper - 0.01 s. With regard to lighting systems, circuit breakers with characteristics AT and FROM, devices with characteristic D are applied to protection of powerful electric motors, and also on input at large consumers of the electric power.

When designing electrical installations, a prerequisite is reliable protection against short circuits at the ends of the wires. The smaller the cross section of the wires, the greater their resistance and, accordingly, the smaller the ratio I kz / I n. At the same time, the smaller the cross section of the wires, the cheaper they are. That is why, when designing lighting systems on traditional sources, before, by default, automata with the characteristic AT.

Do LEDs have inrush currents?

According to its physical principle of operation, the LED does not have any inrush currents - it begins to give light almost immediately after it is applied electricity, without any transients. This circumstance allows some manufacturers of LED lamps to claim that their products supposedly also do not have inrush currents. In fact, this is not always the case.

Starting currents really do not have LED lamps built according to the so-called driverless scheme [L]. But due to the high level of pulsations luminous flux the scope of such lamps is limited.

To protect lighting systems based on traditional light sources, automata with characteristic B were used by default.

In LED lamps powered by the mains alternating current and intended for wide use, as a rule, a capacitor is installed to smooth out ripples. When the lamp is turned on, this capacitor is charged, causing a sharp increase in the current consumed. This is how the concept of inrush currents becomes applicable to LED lamps.

Calculations show that for certain types of drivers, the circuit breaker trips when simply replacing fluorescent lamps with LED ones, even if the current consumption in steady state after the replacement has become less. This problem can often be solved by replacing the automaton with the characteristic AT FROM.

The same can be attributed to retrofit LED lamps powered by AC power (with the exception of the simplest driverless models). In the event that the luminaire uses a driver in the form of a separate module, the multiplicity of the inrush current and the duration of the inrush current are determined by this particular node. Starting characteristics for some drivers from leading manufacturers are shown in Table 2.

Table 2. Starting characteristics of some 230 VAC input driver models

The table shows that the multiplicity of starting currents for LED lamps with drivers exceeds traditional lamps by one or two orders of magnitude!

The multiplicity of starting currents of LED lamp drivers is several hundred due to the presence of smoothing capacitors

In addition, the duration of the inrush current for LED drivers is usually determined at the level of 50% of the maximum value. This value is usually in the range of 100-500 µs. However, such a short pulse is capable of triggering an electromagnetic switch, but it is not as easy to calculate its action as for the inrush currents of traditional light sources.

K \u003d I nd / I p ,

where I nd- rated current of the circuit breaker in terms of one driver, I p- current consumption of the driver in steady state at full load.

The less To, the less likely it is that a situation with a false operation of the circuit breaker will occur. Coefficient To always more I, it depends on the characteristics of the machine. For circuit breakers with characteristic B coefficient To greater than or equal to the coefficient for the characteristic FROM.

And now let's find out where the situation with “knocking out traffic jams” arises when replacing, for example, fluorescent lamps with more economical LED ones. Suppose we are solving the problem of replacing old LPO 4x18 type fluorescent lamps with modern ones. We have a fluorescent lamp with steady state current draw I l. The designers took into account the starting current ratio of 1.5, the fact that the duration of the starting current in real conditions can reach tens of seconds (for example, the lamp does not light up the first time) and took an additional safety factor of 1.25. Then the rated current of the circuit breaker will be

I nl= 1,5 1,25 I l= 1,875 I l

When replacing fluorescent lamps with LED ones with the same luminous flux, energy consumption is reduced by about 2 times. This means that the current consumption of the new lamp I s = 0,5 I l, and the rated current of the circuit breaker I ns = 0,5 K I l.

We use a luminaire with a medium price driver Mean Well LPC-35-1050. For him, when characterizing AT we have To = 5,7.

I ns = 0,5 5,7 I l = 2,85 I l > I nl

This means that the circuit breaker has tripped.

For an automaton with a characteristic FROM we have To= 3.3, then

I ns = 0,5 3,3 I l = 1,65 I l < I nl.

False operation of the circuit breaker at start-up will not occur.

That is, the problem with "knocking out traffic jams" can be solved by replacing the machine with the characteristic AT on an automatic machine with a characteristic FROM and the same rated current. But at the same time, you should make sure that after replacing the machine, the short-circuit current standards for the existing wires will be observed. The specific calculation methodology is beyond the scope of this article, it can be found in reference manuals for electricians.

Leading luminaire manufacturers usually provide information on the recommended types of circuit breakers and the maximum number of devices connected to one circuit breaker. In the absence of such information, you should find out the model of the driver used in the luminaire and find recommendations on the website of the driver manufacturer.

If it is impossible to replace the machine with the characteristic AT on an automatic machine with a characteristic FROM and partially shift the wires in order to comply with the recommendations of the driver (luminaire) manufacturer for the maximum number of devices connected to one machine.

Choice of circuit breaker

Ideally, the manufacturer himself should indicate in the documentation for the luminaire the recommended type of circuit breaker and the maximum number of luminaires that can be connected to it in parallel. In reality, this does not always happen, moreover, as already noted, manufacturers often hide the very fact of the presence of any starting currents in the lamp. You can ask the manufacturer for a driver model and find out the data on the site of the manufacturer of this node. Driver manufacturers are increasingly publishing this information on their websites.

The manufacturer may offer to choose to use, together with his driver, machines with characteristics such as AT, and FROM. If the project requires connecting the maximum number of fixtures to one circuit breaker (for example, there are difficulties with laying wires or there is no place to install extra circuit breakers), then preference should be given to the characteristic FROM. But then, as already noted, it will be necessary to provide an additional margin for the thickness of the wires.

If no selection recommendations are given for an LED luminaire and there is no way to get information about the driver model, you actually have to “play roulette” with an unpredictable result. But there are all sorts of rules of thumb, for example, do not connect more than 8 LED lamps to one machine, use machines with a characteristic FROM instead of characteristics AT etc. These measures make it possible to ensure reliable operation of the lighting system at the cost of introducing excess technological reserves. That is why the availability of recommendations from the driver or luminaire manufacturer on the use of circuit breakers is an additional competitive advantage.

Dealing with high inrush currents

Constantly discussed in specialized Internet forums, the topic of triggering circuit breakers when replacing lamps with traditional light sources with LED ones has already attracted the attention of electronics manufacturers. Abroad, various devices have appeared on the market that, according to their manufacturers, can limit inrush currents. Usually, the principle of operation of such devices is that during the start-up, a resistor is connected in series with the lamp, which reduces the starting current. As a result, the smoothing capacitor in the driver charges more slowly and the start-up time increases, but this is almost imperceptible to users. The disadvantage is that such current limiters are not compatible with all drivers.

Another way, which, according to the author of the article, is more promising is the use of drivers with a small start-up delay, the time of which in a batch varies from instance to instance. The delay time for each driver during their production is set randomly, or according to a certain pattern. As a result, the simultaneous launch of two or more drivers is unlikely or even excluded. Adding such a function slightly increases the cost of the driver, but due to savings in installation work, the increase in price pays off many times over.

Literature

// Electrotechnical market, No. 1 (73), 2017, pp. 16-20.

Alexey VASILEV

Electrical panels and various control panels are widely used in industries, public buildings, and there are also options for use in domestic conditions. Without exception, all electrical circuit control units can be equipped with special light signal lamps, control buttons and various switches. This equipment has a variety of purposes and applications, but in general it performs the function of monitoring and controlling electrical circuits or monitoring the functioning of various equipment.

Electrical panels, mainly produced based on the wishes of the user on an individual order, and are equipped with various control modules. Users actually build their own electrical circuits and for their control and management use various modules for all kinds of switching and light indication of process control. All modules installed in the power grid are divided into two types: informing and controlling. There are also combined versions of modules that are capable of performing both functions.

To informing all kinds of indicator lights , which consist of two parts, namely the module itself and the lamp for light emission, and can be installed in any electrical panel or control panel. The indicator, functioning on LEDs, has a long service life, which is equal to 6000 hours. All indicator lights can be quickly mounted or dismantled and have a wide range of colors, so the user is not limited in any way when choosing these devices. This type devices are used on boards and control panels in order to quickly attract the user's attention and indicate the ongoing process in real time. Any digital sensor or measuring device it is required to constantly monitor, and the indicator light just lights up, thereby making it clear about the state of the process.

Control modules- these are all kinds of switches, toggle switches and just control buttons. This type of modules can be fixed permanently or be portable. Fixed modules are used in places where the technical process does not require movement. Various toggle switches and switches can have a varied range of switching, so the user can choose the module he needs.

Some buttons and switches have special protection to prevent accidental pressing, which can lead to detrimental consequences. This protection includes special button caps, or even locks that are inserted into the button itself, and it is required to turn the key to activate the module. There are also buttons with a large cover, they are made for emergency termination of processes. Thanks to the large button, the user can simply hit it, thereby triggering the module, which is very effective in emergency situations.

All signal lamps, switches and various control buttons, have good protection and can be exposed to any external influences.