Purpose, selection and connection of the automatic phase changeover

Automatic phase changeover

In some cases, industrial, and sometimes household single-phase lines are powered from a network with three to four phases. In order to select a phase with a voltage corresponding to the parameters of the line, an automatic phase switch is installed in the circuit. This device provides an uninterrupted supply of voltage, and also protects the connected devices from surges that can cause equipment failure. The automatic phase switch is connected to a three-phase or four-phase network, through which electricity is supplied to the single-phase line. One of the phase conductors at its output is connected to the protected circuit. When the voltage parameters on it go beyond the normal range, the device switches the mains to power from another cable.

Switch Operation

The automatic switch is a digital device based on microprocessors. The device is durable and has high accuracy, which allows to provide reliable protection of the equipment connected to the network.

When connecting the device to the line, any phase conductor can be selected as the supply conductor.

Phase switch connection example

To prevent the contacts of the output relays built into the device from sticking, the device is equipped with an internal interlock. In addition, it monitors the state of the contacts of the starters, which are available in the external electrical circuit. Using this device prevents phase overload.

ACE installation parameters

The following settings are typical for the models of these devices:

  • Ultimate stress (upper and lower). The maximum voltage indicator is the most significant, and it is important to choose it correctly, without making a mistake when setting up. If it is too low, then the device will constantly work, and if the selected value is too high, overheating of the internal wiring is inevitable, which can lead to a fire.
  • Priority ACE phase. If there are no voltage drops on it, the device will not switch to other lines. In case of drops, the line power will be switched to another conductor, but at the same time the device will continue to monitor the priority core. When the potential difference across it is normalized, the load will switch back.
  • On time. This term refers to the delay period after the voltage disappears on all live conductors. When it expires, the device will try to turn on the power again.

Regulators on analog and digital phase switch

  • Return time. This is the interval after switching the power supply from the priority core to the reserve one, after which the device will check the main phase, and if its parameters are normal, it will switch the power supply to the line. If the priority conductor is not ready to connect the load, the test will be repeated after the same time interval.

Features of connection and operation of the device

Installation of the automatic switch is carried out immediately after the electricity meter. The device connected to the line tests the condition of the conductors and connects the circuit to the core, the parameters of which correspond to the required maximum. During operation, the device constantly monitors the voltage, which should not go beyond the established limits.

The order of operation and the device of the phase switch on the video:

During operation, voltage control is carried out not only on the priority phase, but also on two backup ones. This is necessary so that in case of violation of the parameters on the main conductor, without delay, select another core for switching the power supply.If the voltage on both backup lines is within the permissible limits, switching goes from L1 to L2 and further (the phase designations are on the instrument case, each has its own LED).

Phase switch installation diagram

If the potential difference does not correspond to the specified parameters on any conductor, power will not be supplied through them. When the voltage on the priority line is normalized, it will be connected to it first.

The main types of ACE

In modern networks of our country, the most common models of switches are PF 431 and PF 451. Let's consider them in more detail.

PF 431

This device provides reliable protection of household equipment from voltage surges on phase conductors. It can be installed along with air conditioners, refrigerators and freezers, computers, alarm and video surveillance systems and other equipment that must be continuously supplied with electricity.

The device works according to the following principle. A three-phase voltage is connected to the ACE input, a single-phase network with parameters 220V, 50Hz is connected to the output. The device monitors the output potential difference, and if it goes beyond the set limits, it connects the line to the phase conductor, the parameters of which are correct. At the same time, control over the priority conductor, which for this model is L3, does not stop.

Phase switch in the lead-in box

When the voltage on it normalizes, a reverse connection occurs. If the potential difference across L3 is stable, there will be no power reconnection to the backup phases.

PF 451

This device is designed to ensure the stability of the supply of single-phase lines. It is used with a variety of consumer electronics, like the PF 431, and works in a similar way, which need not be described again. The main difference between the two is that the PF 451 does not have a priority phase. Therefore, for connection, a line with optimal voltage indicators is always selected.

The principle of operation and installation of an electrical circuit based on a phase switch in the video:

Conclusion

The phase switch is not only automatic, but also manual. However, an electronic device is more convenient to use because it does not require control and intervention. To ensure reliable protection of household equipment, it is enough to correctly configure the ACE, and you will not have to worry about the safety of the equipment.

We advise you to read:

Economical electric heaters - myth or reality?