Modern technologies make it possible to control and protect equipment in a three-phase current network. The most detrimental effect on the performance of electrical equipment can be "phase imbalance", this phenomenon manifests itself in the fact that a voltage of a different value flows in each phase of the network. The voltage difference in each phase causes overheating of the windings of motors and transformers, thus putting them out of action. To avoid such consequences, such an equipment control element as a phase control relay was developed. This device allows you to control significant drops and phase failures, as well as their distortion.
Phase control relay
The relay is an electrical equipment designed to control the correct and high-quality voltage supply to the network. The phase control relay itself does not often perform its function, mainly when switching, or in emergency situations in a three-phase voltage network. The absence of such a relay in power circuits can increase the time for connecting and configuring equipment. It is worth remembering that this relay is installed in the network only with three-phase voltage.
Destination
Phase control relays are installed in equipment that undergoes frequent switching and transfer, as well as where correct phasing is important so as not to damage the equipment.
Due to the fact that incorrect phasing in some installations can lead to serious malfunctions, certain types of compressors are referred to such installations. If the phases are connected incorrectly, an operating time of up to 5 seconds is enough for the compressor to fail. Also, if the power is connected incorrectly, the repair team may spend time finding out the reasons for the incorrect operation of the equipment, which could have been avoided by having a phase control relay in the circuit.
Pros and cons
Let's consider the advantages and disadvantages using the example of the EL phase control relay. The advantages of such a relay are considered primarily affordability, in contrast to foreign analogues. Also, the use of such a relay as a power supply is the use of the mains voltage of the installation itself, where the relay is installed. Foreign analogues require separate sources for their power, which complicates the control schemes.
Domestic phase control relays are designed to work in difficult conditions, such as subways and metallurgical enterprises. In three-phasenetworks of such enterprises and installations there are strong distortions, in which foreign analogues cannot cope with their role. The operating temperature range of domestic relays reaches -45 °С.
The disadvantages include increased heat generation during the operation of domestic models. In circuits with analog EL signal processing, the phase monitoring relay often malfunctions. Also, the disadvantages of this model include the outdated case design, as well as the quality of the material used in the manufacture.
Working principle
In almost every electrical installation there are electric motors and transformers, the quality of the installation itself depends on the proper functioning of which. To avoid failures, they use a phase control relay. The relay itself has a circuit that calculates the correct phase order to output the power contacts.
It is recommended to install the relay in the emergency control network, when this is turned on in emergency mode, the entire installation will turn off completely, preventing equipment elements from failing. The relay itself is activated in up to 3 seconds, turning off the unit in case of an accident. During normal operation, the unit is also switched on with a time delay of up to 10 seconds.
