Modern technologies make it possible to control and protect equipment in a three-phase current network. The most detrimental effect on the operability of electrical equipment can have a “phase imbalance”, this phenomenon manifests itself in the fact that voltage of a different value flows in each phase of the network. The voltage difference in each phase causes overheating of the windings of the motors and transformers, while disabling them. To avoid such consequences, an equipment control element such as a phase monitoring relay has been developed. This device allows you to control significant drops and disappearing phases, as well as their distortion.
Phase control relay
The relay is an electrical equipment designed to monitor the correct and high-quality supply of voltage to the network. The phase control relay itself does not often perform its function, mainly during switching, or in emergency situations in a three-phase voltage network. The absence of such a relay in the power circuits can increase the time of connecting and setting up the equipment. It is worth remembering that this relay is installed in the network with only three-phase voltage.
Appointment
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 improper phasing in some installations can lead to serious malfunctions, a certain type of compressor is referred to such installations. If the phases of the working time are incorrectly connected, up to 5 seconds is enough for the compressor to fail. Also, if the power is connected incorrectly, the repair team can spend time figuring out the reasons for the equipment not working properly, which could have been avoided by having a phase monitoring relay in the circuit.
Advantages and disadvantages
Consider the advantages and disadvantages of the example of an EL phase control relay. The advantages of such a relay are primarily considered to be affordability, unlike foreign counterparts. Also, the advantage of using such a relay is the use of the network voltage of the installation itself, where the relay is installed, as a power supply. Foreign analogues, however, require separate sources for their power supply, which complicates control schemes.
Domestic phase control relays are designed to operate in difficult conditions, such as the subway and metallurgical enterprises. In the three-phase network of such enterprises and installations, strong distortions arise, in which foreign analogues do not cope with their role. The operating temperature range of domestic relays reaches -45 ° C.
The disadvantages include increased heat during the work of domestic models. In circuits with analogue EL signal processing, the phase monitoring relay often malfunctions. Also, the obsolete design of the case, as well as the quality of the material used in the manufacture, can be attributed to the disadvantages of this model.
Principle of operation
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 malfunctions, they use a phase monitoring relay. In the relay itself there is a circuit that calculates the correct phase order, according to which the power contacts are output.
It is recommended to install the relay in the emergency monitoring network, with this inclusion in emergency mode, the entire installation will turn off completely, preventing the equipment components from failing. The relay itself operates in up to 3 seconds, disabling the installation in an accident. During normal operation, the unit is switched on also with a time delay of up to 10 seconds.