What is a phase monitoring relay and where is it used?

Design

Modern microprocessor mechanisms that are used in the manufacture of the device provide it with ease of setup, simplicity of design and high reliability of the parameters. If the equipment is imported, this is especially important, since they are particularly demanding on power supply and require a high-quality power network. After all, even a minor accident can cause large losses and failure of expensive equipment.

The following is the connection diagram of the device:

The design of the phase monitoring relay is based on a microcircuit. It is she who directs his work. As soon as the voltage decreases (or completely disappears) on one of the phases, the microcircuit transmits a signal to an electromagnetic relay, which disconnects the load.

Also, the design of the RKF may include indicators of alternation and asymmetry of phase voltages, as well as a response time regulator.

Appointment

Since electrical equipment is used in almost all enterprises and protect it from phase imbalance, as well as mains voltage drops it is necessary constantly, the relay is applied in many fields 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 why relays of this type are used from the video:

This unit may also have a function. voltage monitoring relay - monitors the magnitude of the voltage and turns off the power at values ​​below the setpoint.

Principle of operation

The principle of the device is self-resetting: the relay is disconnected when an alarm is triggered. Upon receipt of a three-phase voltage on the mechanism, all working and controlled parameters are checked.

If during the check all the parameters turned out to be normal, then the built-in electromagnetic relay is turned on. If the control showed that at least one of the parameters does not correspond to the norm, then the mechanism automatically turns off. Then, after returning all the parameters to the permissible norm, 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 disconnected by the device. Emergencies can be different, for example:

• any phase is gone;
• exit from the permissible limits of the voltage level (symmetric or asymmetric);
• incorrect connection of three-phase power, as a result - incorrect rotation.

Such control with the help of such a design allows you to quickly and efficiently protect equipment from dangerous and emergency power supply modes of the electrical network, as well as to monitor the quality of the consumed electricity.

Device types

There are a large number of phase monitoring relays on the market today. One of the most popular species are the following:

• EL-13;
• EL-12;
• EL-11.

In addition, modifications and models such as EL – 12 MT and EL – 11 MT gained popularity and fame.

The EL-11 model and its modification of the EL-11 MT are used, as a rule, to protect generating sets, power supplies, as well as in automatic transfer switch (ATS) schemes.

The relay model EL-12 and its modification EL-12 MT are mainly used to protect electric motors of lifting equipment with a capacity of not more than 100 kW.

Model EL-13 and its modification EL-13 MT carry out control in reversible electric drives with a capacity of not more than 75 kW.

There are two ways to fix the device. The first option is fastening with fixing screws, and the second option is fixing on DIN rail.

So we examined the purpose, principle of operation and the device relay phase control. We hope that now it has become clear to you what this unit is and why it is needed!

We recommend you to familiarize yourself with:

• How to choose a thermal relay for the engine
• How to assemble a three-phase shield with your own hands
• How to check phase rotation