Selection of machines for LED lamps. Circuit breakers and protection modules
Our company "Yug-Service" (Rostov-on-Don) is engaged in wholesale and retail supplies of various products related to LED lighting. In the catalog you will find circuit breakers from the Italian brand Legrand, as well as miniature surge protection modules. Automatic machines (type C) differ in current strength - from 10 to 63 Amperes. Protection modules are designed for voltages up to 1.2 kV.
Switches with surge protection
We offer Legrand MCB circuit breakers (type C) in six modifications: 10 A, 16 A, 25 A, 32 A, 40 A and 63 A. These devices provide reliable protection of electrical equipment from voltage surges, line overloads and other emerging problems . In addition, circuit breakers (type C) provide effective protection of humans from high voltage.
Protection modules are manufactured in South Korea and are intended for lighting equipment. They protect lamps of various types from voltage surges. The maximum lamp power is 15 W.
Type C modules and circuit breakers
Our company sells Italian circuit breakers (type C) only in wholesale, modules - retail sale is possible, wholesale starts from 10 units. High quality products from trusted manufacturers are offered at very competitive prices. A detailed description of the products is posted on the website, or you can consult our employees. They have an excellent knowledge of the range and are always ready to help you make a choice and purchase the best electrical equipment. We work throughout the Russian Federation, and also supply goods to the CIS countries.
Circuit breaker - This is an automatic protective device designed to turn off short-circuit currents and shutdown 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 is often used for residential electrical wiring, will burn like a sparkler at such currents. And it would not be surprising if this leads to a fire.
The second protection of the circuit breaker is the overload protection of the wires.
And again, it is very important to remember that it is the wiring that is protected. Since when too much load current flows through the wire, exceeding the rated one at least two or three times, the wire will become very hot, and eventually 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 a correctly selected circuit breaker, and now I suggest you move directly to the consideration of the criteria for selecting circuit breakers.
Selecting the circuit breaker rating
At , the first thing you need to pay attention to, and in general, let’s say, know in advance before you go to buy, is the rating of the circuit breaker. That is current, which would normally flow through this circuit breaker. And if the rated current is exceeded, the machine will turn off.
The current that will turn off the switch must be selected based on common sense. That is, if, for example, you have 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 based on the condition of ensuring the safety of the wiring, that is, choose the circuit breaker closest in rating to 10 A.
It also follows from this that you will have to periodically change the wiring, since as the number of electricity consumers increases, the load also increases. And over time, the old wiring is simply not capable of allowing such a large current to flow.
Electrical wiring is exactly the case in which it is appropriate to say: “The miser pays twice.” Therefore, if you are replacing electrical wiring, choose the wire cross-section with a margin.
Selecting a circuit breaker class.
You may be aware of such a phenomenon as inrush currents.
Starting currents- this is the current that flows when any consumer of electricity is turned on, 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 trip on inrush currents, like short circuit currents, there is such a thing as a circuit breaker class.
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.
WITH- 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 classes B and C.
Selecting the selectivity of the circuit breaker.
Selectivity - this is the property of protective automation to turn off only damaged sections of the electrical circuit. And to ensure this property, it is necessary to correctly select both the rating and the class of the circuit breaker.
To achieve selectivity of shutdown, the rating of the input switch must exceed the ratings of all circuit breakers in the group. And correspond to the maximum permissible load that the supply wire and apartment wiring can withstand.
Automatic switches of groups are selected based on the current that will flow through them.
Thus, in the event of a short circuit, say, in one of the sockets, only the circuit breaker of the socket group will turn off, and not the input circuit breaker.
Short circuit currents
Also with choosing a circuit breaker its breaking capacity should also be taken into account. Indeed, with 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 circuit breaker that can disconnect currents of up to 3-4.5 thousand amperes. They will cost more, but consider it an investment in your safety. After all, imagine what will happen if your circuit breaker simply cannot, due to circumstances, turn off the short circuit...
Selecting a circuit breaker manufacturer.
As for choosing a manufacturer, many people are often interested in which country it was made in, but this is not entirely the right approach, since components are made in different places, and are even purchased from other manufacturers. Therefore, when choice It’s better to trust the manufacturer’s brand or the seller’s advice; after all, the seller has good purchase statistics and knows what circuit breakers they buy more often and make complaints less often.
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, installed on DIN rails in electrical panels. In everyday life, they actually act as automatic traffic jams.
Selection parameters for modular circuit breakers
The price of modular AVs depends on the design, dimensions and technical parameters.
Rated voltage. Depends on the insulation resistance of the housing material.
Rated current. Should slightly exceed the rated load current. If there is excess “reserve”, the machine will not work at the moment 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 permissible I for conductors, they will burn out, but the machine will not trip.
Breaking capacity. This is the highest short circuit overcurrent at which the switch opens the circuit and is not destroyed. The higher the indicator, the better, but the prices for “automatic traffic jams” with a large shutdown capacity are quite high.
Time-current response characteristics. Inrush currents of equipment under the influence of transient processes far exceed the rated ones. To prevent the machines from tripping during short-term triggering current, they are produced in several types:
B. Only for active loads (lamps, electric ovens, irons);
C. For home and offices (refrigerators, washing machines, computers);
D. For networks with significant reactive load (powerful electric motors).
The ABC-Electro online store offers you to buy modular circuit breakers at an affordable price. On the website you can view the catalog, which shows the current cost of the product, and place an order. If you have questions about the assortment or delivery conditions, our managers will promptly answer them by calling the hotline.
Not every manufacturer lists inrush currents for luminaires in their catalogue.
The catalog of the SLICK.PRS ECO LED 45 5000K lamp indicates a starting current of 35 A. The lamp power is indicated at 42 W.
Recently on my channel youtube There was a video where I gave an example of how I would do task lighting. I was hoping that they would ask me, what about the starting currents, won’t the C6 automatic machine work? For some reason no one paid attention to this.
The fact is that now I will try to prove to you that in most cases you can ignore the inrush currents of LED lamps.
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 starting 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 inrush current for all lamps will be approximately the same.
Let's do some math and justify everything with numbers.
Estimated current for 50 lamps: 0.2*50=10 A.
Starting current of one lamp: 35 A.
Starting current for 50 lamps: 50*35=1750 A.
Let's choose a circuit breaker with characteristic C16.
Ratio of starting current to rated current of the circuit breaker: 1750/16=110.
Let's determine what the duration of this starting current must be for the electromagnetic release of the C16 circuit breaker to operate.
I will round up, thus setting the basis for the strength of our calculation.
From the graph we can say that the inrush current should have a duration of approximately 0.005 s or 5 ms. And this is 100 times longer (if we count 5 μs) than the duration of the inrush current of our LED lamp.
Now let's check whether the machine will work if the current reserve is only 20%.
Initial data: 40 lamps.
Estimated current of one lamp: 0.2 A.
Estimated current for 40 lamps: 0.2*40=8 A.
Starting current of one lamp: 35A.
Starting current for 40 lamps: 35*40=1400 A.
Let's choose a circuit breaker with characteristic C10.
Ratio of starting current to 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 operate.
Conclusion: when choosing LED lamps, inrush currents have virtually no effect on the choice of the rated current of the circuit breaker if the circuit breaker characteristic is “C” and the current reserve is at least 20%. I recommend that the circuit breaker reserve for LED lamps be 20-40%.
On lamps, I think there will be an article or video on youtube, where I will tell you about some features and nuances that you need to know about when choosing lamps.
Over the past five years, LED lights have gone from exotic gadgets for green lifestyle enthusiasts to everyday items. Therefore, it is not surprising that the installation of such lamps is increasingly being carried out not by top-class engineers as part of projects of national importance, but in the most ordinary offices by ordinary electricians or in general by people who have only the most basic understanding of electricity. And what a disappointment it can be when, when turning on seemingly “economical” LED lamps, a circuit breaker is triggered, chosen, it seems, in compliance with all the rules. Or a paradoxical situation arises when, when replacing fluorescent lamps with LED ones, a fuse is triggered, which previously “held” very “gluttonous” Soviet-made devices without any problems. It's time to lose faith in the efficiency of LED lamps. Problems arise because the most important parameter of any lamp is not taken into account - the inrush current value. Moreover, this approach is imposed by the lamp manufacturers themselves, who often claim that their products simply do not have inrush currents.
When an electrical device is turned on, transient processes are usually observed. In addition, starting the device may require more power than in steady state. Because of this, a phenomenon called inrush current is observed. The inrush current value is equal to the maximum input current value when the device is turned on. The inrush current is expressed either in absolute values or as a multiple of the maximum value of the input current divided by the current consumed in steady state. Another important value is the duration of the inrush current - the time during startup during which the input current of the device exceeds the current consumption in steady state.
The presence of inrush 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 heated to the temperature when it glows. Accordingly, the starting current of an incandescent lamp is 10-15 times greater than the consumed current in steady state.
This, by the way, is why incandescent lamps (and halogen lamps, which are similar in operating principle) most often fail when turned on.
In discharge light sources, upon startup, energy is spent on creating plasma between the electrodes, that is, an electrical discharge that produces a glow. Such light sources include, for example, sodium lamps, metal halide lamps and fluorescent lamps. Data on the frequency 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 inrush current ratio. But transition processes occur faster in them. The start-up time of discharge lamps, especially HPS and MGL, is much longer, which forces significant current reserves to be included when calculating wiring.
Time-current characteristics of protective circuit breakers
Modern circuit breakers ensure that the circuit opens when at least one of two events occurs - a prolonged excess of current consumption I above nominal value I n and short circuit. In the first case, an inertial process of opening the bimetallic contacts occurs when heated. Opening occurs when 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 triggered, opening the contacts. Response time graph t c from the ratio I/I n called time-current characteristic.
Existing time-current characteristics are divided into three main groups: IN, WITH And D. Classification is carried out according to the relative value of the current I short, in which an instantaneous electromagnetic trip occurs, that is, when the machine detects a short circuit. For group B the value I short ranges from 3 to 5 I n, For WITH- 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 limit - 0.01 s. In relation to lighting systems, circuit breakers with the characteristics IN And WITH, devices with characteristic D are used to protect powerful electric motors, as well as at the input of large electricity consumers.
When designing electrical installations, reliable protection against short circuits at the ends of the wires is a prerequisite. The smaller the cross-section of the wires, the greater their resistance and, accordingly, the lower 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 based on traditional sources, previously, by default, machines with the characteristic IN.
Do LEDs have inrush currents?
According to its physical principle of operation, the LED does not have any inrush currents - it begins to produce light almost immediately after electric current is applied to it, without any transient processes. This circumstance allows some manufacturers of LED lamps to claim that their products allegedly also do not have inrush currents. In fact, this is not always the case.
LED lamps built according to the so-called driverless scheme [L] really do not have inrush currents. But due to the high level of light flux pulsations, the scope of application of such lamps is limited.
To protect lighting systems based on traditional light sources, automatic machines with characteristic B were used by default
In LED lamps powered by alternating current and intended for widespread 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 current consumption. This is how the concept of inrush currents becomes applicable to LED lamps.
Calculations show that for certain types of drivers, the circuit breaker is triggered when simply replacing fluorescent lamps with LED lamps, even if the current consumption in steady state after the replacement has become less. This problem can often be solved by replacing the machine with the characteristic IN WITH.
The same can be applied to LED retrofit lamps powered by AC power (with the exception of the simplest driverless models). If the luminaire uses a driver in the form of a separate module, the multiplicity of the starting current and the duration of the starting current are determined by this particular unit. Starting characteristics for some drivers from leading manufacturers are shown in Table 2.
Table 2. Starting characteristics of some driver models with 230 VAC input voltage
| Rated current consumption at full load, A | Starting current ratio | |||||
|---|---|---|---|---|---|---|
| For characteristic B | For characteristic C | For characteristic B | For characteristic C |
|||
| Mean Well LPC-35-1050 | ||||||
| Mean Well ELN-30-12 | ||||||
| Osram Optotronic Fit 50/220 | no data | no data |
||||
| Osram Optotronic Element LD 30/220 | no data | no data |
||||
| Philips Xitanium Constant Current Xtreme | no data | no data |
||||
The table shows that the inrush current multiplicity of LED lamps with drivers exceeds traditional lamps by one or two orders of magnitude!
The inrush current multiplicity of LED lamp drivers is several hundred due to the presence of smoothing capacitors
In addition, the duration of the starting current for LED drivers is usually determined at 50% of the maximum value. This value, as a rule, lies in the range of 100-500 µs. However, such a short pulse can trigger an electromagnetic circuit breaker, but calculating its action is not as simple as for the inrush currents of traditional light sources.
K = I nd / I p ,
Where I nd- rated current of the circuit breaker in terms of one driver, I p- driver current consumption in steady state at full load.
The less TO, the less likely it is that a situation with a false triggering 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 higher than or equal to the coefficient for the characteristic WITH.
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. Let's assume that we are solving the problem of replacing old fluorescent lamps of the LPO 4x18 type with modern ones. We have a fluorescent lamp with steady state current consumption I l. The designers took into account the starting current multiple 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 lamps with the same luminous flux, energy consumption is reduced by approximately 2 times. This means that the current consumption of the new lamp is I s = 0,5 I l, and the rated current of the circuit breaker I ns = 0,5 K I l.
We use a lamp with a mid-price driver Mean Well LPC-35-1050. For him, when characterizing IN we have TO = 5,7.
I ns = 0,5 5,7 I l = 2,85 I l > I nl
This means the circuit breaker has tripped.
For a machine with the characteristic WITH we have TO= 3.3, then
I ns = 0,5 3,3 I l = 1,65 I l < I nl.
False activation of the circuit breaker during startup will not occur.
That is, the problem with “knocking out traffic jams” can be solved by replacing the machine with the characteristic IN on a machine with characteristics WITH 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 method is beyond the scope of this article; it can be found in reference books for electricians.
Leading luminaire manufacturers usually provide information on the recommended types of circuit breakers and the maximum number of devices that can be connected to one circuit breaker. If such information is not available, you should find out the model of the driver used in the luminaire and find recommendations on the driver manufacturer’s website.
If it is impossible to replace a machine with the characteristic IN on a machine with characteristics WITH and partially re-arrange the wires in order to comply with the driver (luminaire) manufacturer’s recommendations for the maximum number of devices connected to one machine.
Selecting a 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 that the lamp has any inrush currents. You can ask the manufacturer for the driver model and find out the data on the website of the manufacturer of this node. Driver manufacturers are increasingly publishing this information on their websites.
The manufacturer may offer a choice of using machines with characteristics such as IN, so WITH. If the project requires connecting the maximum number of luminaires to one circuit breaker (for example, there are difficulties with laying wires or there is no space to install extra circuit breakers), then preference should be given to the characteristic WITH. But then, as already noted, it will be necessary to provide additional margin for the thickness of the wires.
If recommendations for selection are not given for an LED lamp and there is no way to obtain 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 the characteristic WITH instead of characteristics IN and so on. These measures make it possible to ensure reliable operation of the lighting system at the cost of introducing excess technological reserves. This is why the availability of driver or luminaire manufacturer recommendations for the use of circuit breakers is an additional competitive advantage.
Combating high inrush currents
The topic of tripping circuit breakers when replacing lamps with traditional light sources with LED ones, constantly discussed in specialized Internet forums, has already attracted the attention of electronics manufacturers. Abroad, all sorts of devices have appeared on the market that, according to their manufacturers, are capable of limiting inrush currents. Typically, the operating principle of such devices boils down to the fact that during startup, a resistor is switched in series with the lamp, which reduces the starting current. As a result, the smoothing capacitor in the driver charges more slowly and the startup time increases, but this is almost imperceptible to users. The disadvantage is that such current limiters are not compatible with all drivers.
Another method, which, according to the author of the article, is more promising, is the use of drivers with a slight start delay, the time of which in the 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 completely excluded. Adding such a function slightly increases the cost of the driver, but due to savings on installation work, the increase in price pays off many times over.
Literature
// Electrical market, No. 1 (73), 2017, pp. 16-20.
Alexey VASILIEV