Protection of electrical equipment powered by a three-phase network from low-quality voltage. Three Phase Voltage Relay Phase Sticking
The company has been producing electrical products for a long time, which are in demand around the world. This popularity is due to the fact that the concern’s specialists ABB constantly improve their inventions, use the latest technologies and developments to create a product that meets the world level of quality.
Voltage control relay ABB– a long-awaited product that has made a real revolution in the market of electrical equipment and goods.
Over many years of practice, the concern ABB acquired many regular customers and earned trust among industry experts.
This product ABB - three-phase voltage control relay serves to take readings of the values of low and high voltages, and also checks the sequence in phase rotation and signals a break. When using a mobile three-phase device and this ABB monitoring relay it is possible to ensure the safety of personnel and the equipment itself.
Due to the supply of unstable voltage, damage may occur in the mechanisms and their electrical circuits, which will lead to breakdown of the system as a whole.
Thanks to this relay CM from ABB You can safely switch to additional and emergency power sources.
Phase control relay 3-phase Omron and Zamel
In this article we will consider from all sides a very useful industrial electronics device -, other names - three-phase voltage monitoring relay, open-circuit and phase rotation monitoring relay. From the name you can guess what this thing is - a relay that controls the quality of three-phase voltage and the correctness of its connection.
As always in such articles, there will be theory, diagrams, photos, instructions.
This device performs its function infrequently, a little more often than. However, without it, it happens that unnecessary time is spent setting up equipment. In addition, this device will protect the equipment from poor-quality power supply.
It is important to understand that the phase control relay is only three-phase, and is always connected only to a 3-phase network!
Why do you need a three-phase phase control relay?
The phase control relay must be installed where reconnection to the three-phase supply voltage is often made, as well as where phasing (correct phase rotation) is important.
For example, a phase control relay can be useful in equipment that is often moved from place to place, and in which phase reversal is critical. In some devices, incorrect phase rotation can lead to malfunction and failure. For example, a screw compressor, if turned on in the wrong direction for more than 5 seconds, can completely fail.
In addition, when connecting such equipment, there may be a mistaken opinion that it needs to be repaired, and the repair personnel will scratch their heads for some time until someone gives the necessary thought: “Or maybe the phases are mixed up?” And then someone else will say an even more necessary thought: “We should install a phase control relay...”
Operating principle and functions of phase control relays
So, in each machine there is a correct phase order in which all motors for a given connection rotate in the correct direction. If the supply phases are mixed up, then everything will also spin, but incorrectly, and perhaps not for long.
The phase control relay contains a circuit that calculates phase sequence(Phase-sequence), and in accordance with this order the output contacts are triggered. These contacts can be connected anywhere - to the control circuit, to a bell or light bulb, break the power circuit, the power supply circuit of the entire device or the motor contactor coil.
The last use is recommended by the manufacturer, but I recommend that the entire machine in which this relay is installed cannot start. Naturally, if the emergency circuit is executed correctly, as I recommend in the article at the link provided.
This is the main application.
Other uses - phase loss protection(Phase-loss). Or from a significant drop in voltage on one of the phases ( asymmetry, or phase imbalance) (Three-phase Asymmetry).
The last two functions are basically identical, the only question is the level of voltage drop.
It is also used to protect electric motors against phase failure, but they are triggered by thermal overload, and this is already a critical mode. And the phase control relay is an electronic device, and will work earlier (1-3 seconds), preventing the engine from overheating. In the case of phase alignment, switching on does not occur immediately, but after the required time (5-10 seconds).
The asymmetry voltage level can be set in all phase control relays, but the on/off time, as a rule, is regulated only in sophisticated models. In addition, the asymmetry detection function has a useful parameter called hysteresis, which ensures smoother operation of the device. It is also usually not regulated.
How hysteresis works, ask someone who knows what it is))
Thus, we can say that a phase control relay is a device that controls the quality of three-phase supply voltage in industrial equipment. And naturally, the phase control relay is a 3-phase device.
Design and models of phase control relays
Zamel CKM-01
Let's go from simple to complex. As an example, consider first the relay SKM-01 produced by the Polish company Zamel.
What's new in the VK group? SamElectric.ru ?
Subscribe and read the article further:
The relay has three phases (L 1, L 2, L 3) and zero (N) supplied to the input; the internal circuit is powered from phase L 1. The output relay has one switching contact. There are also two indicators that show phase rotation and asymmetry.
This is what this relay looks like in real life:
The electrical circuit of the CKM-01 Zamel relay is very simple, assembled with only two transistors. The insides of the CKM-01 Zamel can be seen in the photo below.
Honestly, I would never have believed that such a relatively complex device could be assembled with just 2 transistors!
Instructions from the manufacturer can be downloaded at the end of the article.
RNPP-311
Now let's look at the popular domestic model - RNPP-311. Full title - Voltage, imbalance and phase sequence relay. Hence the abbreviation name. For more details, see the instructions at the end of the article.
Recently a relay appeared RNPP-311M, it has a more modern and compact body and more settings.
OMRON K8AB
A more sophisticated model - OMRON K8AB:
Omron K8AB-PA. Appearance
There is already an additional response time regulator. Also, this relay reacts not only to undervoltage, but also overvoltage on one of the phases.
The circuit is assembled on a microcontroller, like all the models that I will consider below.
Timing diagram and diagram located on the side wall of this relay:
Omron K8AB - timing diagrams, setup and circuit
The Omron K8AB relay line includes 4 models, and they provide very advanced settings to suit every taste. The instructions are there.
Another voltage control relay, one of those that I came across -. It is involved in the circuit of an industrial refrigerator compressor, which I wrote about in an article about the use of an Uninterruptible Power Supply Device (UPS) or something else.
At the input there are three phases, at the output there are two relays, the contacts of which in this case were connected to the circuit in series and cut off the power circuit of the control circuit. In addition to the four settings regulators, there are also operating mode switches under a cover with a broken seal.
In that article, I did not write that I tried to start this refrigerator by excluding this relay from the circuit. But Carlo Gavazzi was right - the compressor did not want to start with such poor voltage quality.
Euroautomatika FiF CKF-318-1
A device for a three-phase relay for monitoring and presence of phases from a Belarusian manufacturer. The device and a real example of connection and installation in a compressor are shown.
Phase control relay connection diagram
If the equipment uses only frequency converters to connect electric motors, then a phase control relay is not needed - for the frequency converter it doesn’t matter in what order the phases arrive at it, it still rectifies the three-phase alternating voltage and converts it to direct voltage.
However, I recommend installing such a relay in any industrial equipment costing over $1000 with three-phase power. After all, the relay itself costs a little more than 1000 rubles (domestic models), and in case of problems with power supply it will immediately let you know about it.
So, here are a few connection diagrams that manufacturers recommend. In principle, there are few differences.
- this is an unpleasant moment that negatively affects electrical equipment connected to the network at that moment. After all, it is the order of the phases and the voltage across them that makes electrical machines, such as motors and transformers, work. To avoid damage, use a relay that monitors the phases. So what is it and where is a similar design used? This device is necessary so that in a three-phase network each phase alternates correctly. If at least one fails, the device protects the equipment. Next we will look at the device, principle of operation and purpose of the phase control relay.
Design
Modern microprocessor mechanisms, which are used in the manufacture of the device, provide it with ease of setup, simplicity of design and high reliability of parameters. If the equipment is imported, then this is especially important, since they are particularly demanding on power supply and require a high-quality power supply network. After all, even a minor accident can cause large losses and failure of expensive equipment.
Below is a diagram of the device connection:
The design of the phase control relay is based on a microcircuit. It is she who directs his work. As soon as there is a decrease (or complete loss) of voltage on one of the phases, the microcircuit transmits a signal to an electromagnetic relay, which turns off the load.
Also, the RKF design may include indicators of phase voltage rotation and asymmetry, as well as a response time regulator.
Purpose
Since electrical equipment is used in almost all enterprises and it is constantly necessary to protect it from phase imbalance, relays are used in many areas of activity.
The mechanism is used to protect three-phase devices. The phase control relay protects against breaks, distortions or sticking, and also controls that each phase alternates correctly.
You can learn more about what relays of this type are used for from the video:
This device may also have a function - it monitors the voltage level and turns off the power at values below the set value.
Principle of operation
The operating principle of the device is self-resetting: the relay turns off when an alarm is triggered. When three-phase voltage is supplied to the mechanism, all operating and controlled parameters are checked.
If, during the check, all parameters are normal, then the built-in electromagnetic relay is turned on. If the control shows that at least one of the parameters does not correspond to the norm, then the mechanism is automatically turned off. Then, after all parameters return to acceptable levels, the device automatically turns on without delay. If not one phase is turned off, but two or three, then the device can turn off without delay.
When any emergency occurs, the load is switched off by the device. Emergency situations can be different, for example:
- any phase is missing;
- exit from the permitted voltage level limits (symmetrical or asymmetrical);
- erroneous connection of three-phase power, resulting in incorrect alternation.
Such control using a similar design allows you to quickly and efficiently protect equipment from dangerous and emergency power supply modes of the electrical network, as well as monitor the quality of consumed electricity.
Device types
There are a large number of phase control relays on the market today. Some of the popular types are the following:
- EL–13;
- EL–12;
- EL–11.
In addition, modifications of such models as EL-12 MT and EL-11 MT have become widespread and famous.
The EL-11 model and its modification EL-11 MT are used, as a rule, to protect generator sets, power supplies, as well as in automatic transfer switching (ATS) circuits.
The relay model EL-12 and its modification EL-12 MT are mainly used to protect electric motors of lifting equipment with a power of no more than 100 kW.
The EL-13 model and its modification EL-13 MT perform control in reversible electric drives with a power of no more than 75 kW.
The device is fixed in two ways. The first option is fastening using mounting screws, and the second option is fixing to.
So we looked at the purpose, principle of operation and design of the phase control relay. We hope you now understand what this device is and what it is needed for!
At any industrial enterprise, protection of consumer devices powered by a three-phase network is necessary. To protect electrical equipment from undesirable consequences and failure, stabilizers or phase control relays are used.
In addition to the decrease and increase in voltage in the three-phase current network of each phase, there is a danger of other emergency conditions.
“Phase imbalance” is a phenomenon that occurs when the load is unevenly distributed on each of the phases, that is, the voltages on the phases are different, while the amplitudes of the phase and linear voltages and the angles between them are not equal to each other. An ideal model showing the relationship and relative position of phase and line voltages in which there is no imbalance of phase voltages can be seen in the figure. Linear voltages (380V) – vectors AB, BC, CA. The phase voltages are also equal to each other - these are the vectors 0A, 0B, 0C, which are located at 120º to each other.
If several consumers are unevenly connected to the phases, including single-phase ones with different resistances and at different times, and also often different in nature: active (resistive) or reactive (inductive or capacitive), then at every random moment in time one can expect that the total loads in different phases will be different. The difference in phase loads in size and nature creates conditions for the occurrence of phase voltage imbalance. The consequences of phase imbalance are manifested in an increase in power consumption due to incorrect operation of consumers, in their failures, shutdowns, overheating, blown fuses in devices, thermal wear of insulation and burnout of motor windings.
In addition to phase imbalance, there is a danger of phase breakage or sticking:
If the network fails, all three phases can have a voltage of 220 V. In this case, two phases are closed to each other. This situation is called phase adhesion. “Sticking” of phases is a phenomenon when only one (without shift) phase voltage arrives through two supply wires of the network. At this voltage in the network, any electrical equipment fails.
For the normal operation of electrical devices and consumers (mainly electric motors), a certain order of phase alternation of the supply voltage is needed; it can be controlled using phase control relays produced in various modifications.
The principle of operation of the EL phase control relay is based on the self-reset mode; the measuring part of the relay uses a transformerless circuit using rectification of phase voltages. When three-phase voltage is supplied to the EL relay, all voltage parameters in the network are checked. If all parameters are normal, then the built-in electromagnetic relay turns on and the circuit closes. Voltage is supplied to consumers and devices.
If any parameter of the network voltage is outside the permissible value, the relay opens the network and the equipment stops operating. This action is accompanied by the lighting of the red LED on the front panel of the EL relay. When the voltage parameters in the network return to normal, the relay closes the circuit again and power is supplied to the devices. During normal operation, the green LED on the relay panel lights up.
The phase control device monitors the voltage quality in the electrical network throughout the entire operating time.
The advantages of models from the EL series include their low cost. Domestic devices cost from 700 to 1,500 rubles, while imported ones from manufacturers such as ABB, TELE, Lovato, Schneider Electric, Omron, Finder cost from 3,000 rubles. In times of financial instability, many enterprises and factories such devices are not available for use.
The power supply of many imported relays requires a different source of electricity, different from the controlled one, and this complicates their connection diagram when domestic phase control relays are powered from a controlled network. Imported models are not designed to operate at temperatures below -25ºС, when domestic relays can withstand air temperatures down to -40ºС, for example EL-11 with climatic modification U3 from the Kyiv Relsic plant (Ukraine). In our country, the regions differ significantly in climatic conditions and these relays find their use in harsh arctic and subarctic climatic zones.
Domestic electricity is, to put it mildly, of low quality. This applies not only to the Russian Federation, but also to almost all CIS countries. It should also be noted that the electrical wiring and electrical equipment of enterprises in the overwhelming majority are also hopelessly outdated, both morally and physically. Therefore, domestic devices and equipment are resistant to voltage surges, because they were originally developed to work in domestic networks. At metallurgical enterprises, on railways, in crane and lifting equipment, they have proven to be more reliable.
But the EL series relays also have disadvantages. Firstly, high heat transfer, which leads to reduced reliability. If the electrical cabinet is poorly ventilated, the device can quickly fail. Secondly, when analog signal processing is in emergency mode, its operation may be incorrect. Manufacturers, unfortunately, are silent about this in the technical documentation. This problem has been solved in models with digital signal processing EL-11M, EL-12M, EL-13M, EL-11M-15, EL-12M-15 and others. And also in phase control relays from Schneider Electric, Omron, Finder, Siemens, ABB and other foreign manufacturers. The comparative characteristics of phase control relays from various manufacturers can be found in the table.
The figure shows a schematic diagram of the phase control relay of the EL-11 modification.
Below is an example of a diagram for connecting a phase control relay to the electrical power supply network. 
The use of the EL series models is different: EL-11 is used directly to control voltage indicators in the network, EL-12 controls the alternation of phases and “distortion”, EL-13 – only voltage asymmetry, EL-15 – additionally allows you to adjust the ranges of controlled voltages.
Based on the above application areas, the application areas of the relay can be determined. The first type of devices can be connected to the network where the generators of the ATS system operate. Type EL-12 is applicable to protect high-power asynchronous motors that operate in non-reverse mode. Type EL-13 is suitable for protecting three-phase reversible asynchronous motors.
The response threshold, which is indicated by manufacturers in the technical documentation, only works at the normal rated voltage of the two remaining phases. This technical characteristic does not make it possible to fully evaluate the quality of the device. Tests have shown that it operates with voltage deviations of 15-18% with asymmetry.
When a phase failure occurs, many types of motors begin to generate voltage on the phase where the failure occurred. The voltage on it can reach an amplitude of 95%. The difference in amplitudes depends on the type of engine and its operating conditions. Model EL-12, which has digital signal processing, can regulate asymmetry from 5 to 20% of the network voltage. This allows the motor to be stopped if a phase loss is detected.
Another advantage of such a relay is the presence of a minimum switching threshold. It will turn on and supply voltage to the network only if the voltage in the network is within acceptable limits (not lower than 70% of the minimum). It is good to use such relays in networks where pump and compressor motors are powered. In other words, the torque of the shaft does not depend on its rotation speed.
The electrical network parameters controlled by the EL-13E are almost the same as those of the EL-12E. An excellent parameter is phase rotation control. The response time of such devices is from 0.1 to 0.5 seconds. Their optimal use can be on lifting devices (cranes, their booms) for the safe movement of loads and protecting them from falling.
Hello, dear visitors and readers of the Electrician's Notes website.
This article will focus on phase control relays of the EL-11, EL-12, EL-13 types, as well as its modernized models EL-11MT and EL-12MT.
These relays are also called three-phase voltage control relays.
I came across these relays for the first time recently, because they are not widely used in circuits and automation. For these purposes, we use simpler and no less reliable electromechanical relays.
And then the other day a colleague from the “shop” asked to check the EL-11 phase control relay, which was installed in his ATS (automatic transfer switch) circuit at the input of the administrative building. According to him, the phase control relay did not work correctly, and most likely did not work at all.
Upon arrival at the installation site, I discovered that the three-phase voltage relay was indeed not working correctly, i.e. The “network” LED on the relay did not light up, although all three phases (A, B, C) were supplied to the relay.
It was also possible to check the phase rotation, but my colleague convinced me that no repairs had been made and the phasing had not changed.
I suggested checking this relay at our stand and, if it is faulty, then replacing it.
Well, since we removed the relay, we also switched the ATS circuit from automatic to manual mode. But we will talk about this in the following articles, for example, read about. If you don’t want to miss the release of new articles on the site, then go through a simple subscription procedure. The subscription form is located at the end of each article and in the right column of the site.
Purpose of the phase control relay
Relays EL-11, EL-12, EL-13, EL-11MT and EL-12MT are used for:
control of increase or decrease of three-phase voltage
control of phase failure of three-phase supply voltage
control of asymmetry of three-phase voltage of the supply network
EL-11 and EL-11MT are most often used to protect power supplies and converters, generators, as well as in ATS (automatic transfer transfer) circuits.
EL-12 and EL-12MT are most often used for cranes with a power of no more than 100 (kW).
EL-13 is used as protection for electric drives with a power of no more than 75 (kW).
Now let’s take a closer look at each type of relay separately.
The technical specifications are shown in the table below (clicking on the picture will enlarge it).
This is a plate with data on the switching capacity of these relays.
And here are their overall dimensions.
Installation of phase control relays EL-11, EL-12 and EL-13
EL-11, EL-12 and EL-13 are attached in two ways. The first method of fastening is carried out using two M4 mounting screws.
The second mounting method is more convenient in my opinion - DIN rail mounting.
By the way, the passport for this relay says that it can have an arbitrary spatial position.
In general, at least install it “upside down”.
Connection and diagram of relay EL-11, EL-12 and EL-13
Three-phase voltage control relays of types EL-11, EL-12 and EL-13 are connected using clamps. Under each terminal it is permissible to connect either one wire with a cross-section of 2.5 sq. mm, or two wires with a cross-section of up to 1.5 sq. mm.
I remind you that I already wrote an article on the topic of how to determine. You can read it.
To connect everything correctly, you need to know the diagram. In principle, the manufacturers took care of the hint and depicted the connection diagrams on the relay body itself.
By the way, when checking this relay, I discovered that on the bench I had the reverse order of phase rotation of the three-phase voltage source. Instead of A, B, C, the terminals actually showed C, B, A.
So, for a more visual representation of the operation of this relay, I put together the following diagram.
This is what the diagram looks like on the stand.
A three-phase voltage of ~ 110 (V) with correct phase rotation is supplied to the terminals (terminals) A, B, C of the EL-11 relay.
To observe the work of the weekend n.z. (1-2) and n.o. (3-4) relay contacts, I connected SKL LED lamps of red and green colors to them.
On N.Z. (normally closed) contact connected the green lamp, and on the no. (normally open) - red.
Operation of relays EL-11, EL-12 and EL-13
Let's consider several cases of operation of a three-phase voltage control relay.
If there is no three-phase supply voltage at relay terminals A, B, C, the red “network” LED does not light up. Contact (1-2) is closed, (3-4) is open. This is clearly visible from the lamps - the green lamp is on.
When three-phase supply voltage is applied to relay terminals A, B, C, the red LED lights up. Contact (1-2) opens, (3-4) closes. Again, this is clearly visible from the lamp - the red lamp is on.
3. There is voltage at relay terminals A, B, C, but its parameters are outside the permissible limits
Let's consider the case when voltage is present at the terminals of the phase control relay A, B, C, but its parameters exceed the permissible values specified in the technical specifications. At this moment, the red LED on the front panel of the phase control relay goes out, and contact (1-2) closes and (3-4) opens after a period of time set using the regulator.
For relays EL-11, EL-12 and EL-13, the time delay can be adjusted in the range from 0.1 - 10 (sec).
After the network parameters are restored, the red LED on the front panel of the phase control relay lights up again, contact (1-2) opens, (3-4) closes, i.e. the scheme is restored.
As they say, “it’s better to see once than to hear a hundred times,” in general, watch the video about the principle of operation of this relay:
Addition: At the request of readers, I am posting functional diagrams of the relay.
We looked at phase control relays of types EL-11, EL-12 and EL-13. Now let's move on to their modernized “brothers” such as EL-11MT and EL-12MT.
Specifications:
And here are their overall dimensions.
Installation and connection of EL-11MT and EL-12MT
EL-11MT and EL-12MT are mounted either using two mounting screws or on a DIN rail.
Connection and diagram of relay EL-11MT and EL-12MT
Connection of three-phase voltage control relays of type EL-11MT and EL-12MT is carried out in the same way.
The only difference is the marking of the clamps. Instead of A, B, C, these relays use the markings L1, L2, L3. The same situation applies to contacts. Instead of n.z. contact (1-2) is used (11-12), and instead of n.o. (3-4) - (21-24).
In principle, the manufacturers again took care of the hint and drew a diagram for connecting the relay directly on its body.
As an example, we depicted a protection circuit using a three-phase voltage control relay.
Now I’ll tell you how this scheme works.
The electric motor is powered from a three-phase voltage network through fuses. After the fuses, a phase control relay EL-12MT and KM power contacts are installed. The KM contactor is controlled as follows.
The power supply for the control circuits in this example is taken from two phases L1 and L2 (you can also take another line voltage). The KM contactor coil must be selected for line voltage, i.e. if the line voltage of the network is 380 (V), then the KM coil should be at 380 (V).
When you press the SB1 button, the KM contactor is turned on via the circuit: phase L1 - pressed button SB1 - normally closed contact of the SB2 button (stop) - closed contact (24-21) phase control relay EL-12MT - KM contactor coil - phase L2. There is no need to hold down the SB1 button, because when the KM contactor is triggered, the SB1 button is bypassed by its normally open contact KM.
Accordingly, contact EL-12MT (24-21) will be closed if the parameters of the three-phase supply network satisfy all the conditions stated at the beginning of this article.
For example, the engine is running normally. Suddenly, a phase of the three-phase supply voltage disappeared. After 2 (sec.) the relay will open contact (24-21), the KM contactor coil will de-energize and open its power contacts KM. The engine will be disconnected from the network.
When connecting relays EL-11MT and EL-12MT, it is necessary to observe the correct phase rotation order.
Three-phase voltage control relays of type EL-11MT and EL-12MT have slight differences from their predecessors.
1. Trip setpoint regulators for overvoltage and undervoltage
On the front panel of the relay there are 2 regulators for regulating the relay operation setting when the voltage of the three-phase supply network is exceeded and decreased.
You can see their limits in the technical specifications, which I wrote about just above.
2. Regulators for setting the time delay for overvoltage and undervoltage
Using these regulators, you can set a specific time delay for the relay to operate when the supply voltage is over and under. You will find all regulation limits for them in the technical specifications.
3. There are 3 red LEDs on the front panel of the relay
There are 3 red LEDs on the front panel. If one of the phases is broken or the phase sequence of the three-phase supply voltage is violated, the first LED lights up. By the way, I almost forgot to say that when there is a break or change in the phase sequence, the relay is triggered with a set (non-adjustable) time delay of 2 (sec).
When the voltage exceeds the setting, the second LED lights up. And vice versa, when the voltage drops below the set point, the third LED lights up. See table.
P.S. I think this is where we can stop at getting to know and study EL-11, EL-12, EL-13, EL-11MT and EL-12MT. If you have any questions about these relays or need help connecting them, please write in the comments. And also, if you found the article useful, then share it with friends and colleagues on social networks. I will be very grateful to you.