The article will be useful rather for owners of private houses who prefer a three-phase network to a single-phase one. The phase selection relay is a convenient and practical device that determines which phase is close to the nominal voltage. It has 2 undeniable advantages: affordability in terms of price policy and ease of installation.
How does the phase selection relay work?
The phase priority relay is not a very complicated device, for the manufacture of which more than two transistors are rarely used. Constructed so as to read the phase readings and give a signal to turn on a certain contactor. Also, the relay has a phase sequence control circuit, which is very useful when installing power circuits for the operation of motors.
Structurally, the phase priority relay implies the adjustment and setting of the output parameters - you can adjust the voltage sensitivity based on the situation in which it will be used device. On expensive models, an additional timer is installed, which allows you to set the shutdown time of the device or the time for switching between phases.
How to correctly and quickly connect the phase selection relay
One relay in the control room will not be enough: contactors are also installed in tandem with such a device. This should be taken into account in advance, even at the design stage of the electrical wiring, since several of these devices will take up enough space in the dashboard. If the relay is installed as a system upgrade, then a separate panel can be allocated for it and the contactors next to the main one.
Connection sequence for phase relays and contactors:
1. Bring the operating phase to each contactor, connect to the device and mark.
2. Connect the 3 wires from the upper sockets of the relay to the same contacts of the contactors to which the phases are already suitable.
3. Fix the other 3 wires at the control end of the relay and connect to the contactor coils.
There are 2 sockets on the coils: the first one mounts the conductors from the relay, the second one - working neutral wires.
4. Connect the wires coming from the outputs of the contactors to each other and to the fourth conductor, which will go directly to the load.
5. Check the functionality of the circuit.
If the installation is done correctly, the relay will compare the network readings with those installed in the device and select the phase that is closest to the nominal.
On which lines should the phase selection relay be installed
It is best to mount the phase priority relay on those lines whose consumers are most sensitive to potential imbalances. For example, computers, low voltage networks, video surveillance, or places with a lot of other electronics.
Combined models can also be installed on lines with electric motors and consumers for which a phase loss can cause malfunctions (failure). The phase selection relay is a universal device, you just need to figure out where it can be installed.