At manufacturing enterprises and other institutions, strict requirements are imposed on the uninterrupted operation of the power grid. The main means of its provision are automatic input of the reserve used in single-phase power supply networks, and a phase switch, which differs from the classical ABP by the use of additional lines from the inactive phase of a three-phase network.
Device and principle of operation
The input terminals of the device are supplied with power from three phases, and only one comes out of it, having the voltage indicator as close to optimal as possible. When the main line is cut off or a power surge occurs, the three-phase switch activates another phase - where the indicator is closest to normal. For the most part, the device is used in networks with three phases, but it is also used for a generator - in this case, the shape of the triggering pulse should be considered.
Mechanical and automatic devices are available. An automatic three-phase phase switch operates with the support of a microcontroller. By switching the design of several relays, the automatic switch looks for among the power lines the closest to the appropriate indicators. Positional 3-phase manual switches are available with a different number of positions (from two to four). The digital switching order may be different for them. One example: 0-1-0-2-0-3: here, zero indicates the shutdown of all lines, and the remaining digits correspond to the phases. Mechanical devices with high power are often used for reversible motors.
How to choose a phase switch
When choosing a voltage switch, first of all, you need to pay attention to the current parameters for which the device is designed. They determine whether the device is suitable for use in a particular network. It is not recommended to purchase a switch whose current is higher than the rated value for the input machine.
Other significant parameters when acquiring a manual or automatic phase finder are:
- flexibility and variability of settings: at least, the boundaries of the normal voltage and the main phase should be provided;
- type of indication: preferred - liquid crystal display; cheap models use LEDs;
- additional features - for example, touch control.
If it is found that the phase distributor does not have enough power to service the network, you can put a switching device. In this case, the coil of the contactor or starter must be connected to the output terminals of the device.
Scope, purpose and parameters
The scope of the use of phase selection devices is extensive: devices are installed at manufacturing enterprises - in automation, control, ventilation systems and others; in hospitals and pharmacies - life support equipment, storage of medicines. They are also used in residential buildings: to provide signaling installations, gas boilers.
The use of a 3-phase switch is practiced to transfer power from an active line to another. This option is advisable in situations where interruptions, sudden surges occur in the main line, the voltage becomes too high or ceases to be applied at all.To ensure uninterrupted supply of the network and to prevent emergency incidents, it is necessary to correctly set the values of key parameters.
Minimum voltage limit
It shows the limit below which it is impossible to fall, otherwise the network will work intermittently. Set the border in accordance with the documents attached to the device.
Return time
This is the period after which an attempt is made to redirect contacts to the main source when using a backup core. When this period passes, the device checks the parameters of the leading phase. If they correspond to normal indicators, the food passes to it, if not, later a second check is carried out after the same period of time. Using this mechanism makes it possible to save resources - for example, leaving the room equipped with a generator, you can turn off the engine for a certain interval (an hour or two). Turning it off for a long time is fraught with a strong drop in temperature in the cold season and the failure of electrical appliances, and using the indicated option will be a rational solution.
On time
It characterizes the time after which the device will try to turn on the power in a situation of its absence on all current-carrying wires. You can create a signal using a relay.
Connection diagram and procedure
It is recommended that you independently connect the phase switching machine only if you have sufficient experience working with electrical networks, since you will have to deal with high voltage. Incorrect operations can cause an interphase fault. Place the device on a din rail inside the shield. Typically, the installation diagram of the device is described in the attached technical documents. First, the primary circuits are connected, then the secondary ones.
When the master connects the power line switch to the network, he may prefer any of the three phase conductors as the supply wire. To prevent jamming of the contacts of the output relay, the device has a special lock. Also, introducing the device into the circuit prevents overloads. Automatic devices are equipped with the option of monitoring the contacts of the starters of an external electric circuit.
So that the contacts of the output relays built into the device do not stick, the device is equipped with an internal interlock. In addition, it monitors the state of the contacts of the starters that are in the external circuit. Using this device allows you to prevent phase overload.
ACE Installation Parameters
In the technical documentation for the device and on its case two parameters are indicated - the minimum and maximum voltage at which the correct operation of the network is possible. The second is especially important - when it is exceeded, the wiring burns out, which can initiate a fire. If the voltage drops too low, the device will operate all the time.
Of great importance are the time parameters - periods of inclusion and return. In addition, the installer must select the main phase. It is used by default, and if power surges occur on it, a backup core is involved. During its operation, the device continues to monitor the condition of the lead core and, when it returns to normal, switches to it.
Features of connecting and operating the device
As a rule, the device is installed in the circuit after the electricity meter. The connected switch examines the voltage parameters in the cables and connects the circuit to the most satisfying requirements. The device continuously monitors the voltage not only in the main phase, but also in the spare ones, so that if the parameters of the lead core suddenly go beyond the specified limits, immediately select the cable to which the power will be switched.When the parameters are within acceptable limits in both redundant wires, the unit switches from L1 to L2 and beyond. If the potential difference of all cables does not match the specified parameters, none of them will be powered. When the voltage normalizes on the main line, it will be included in the circuit.
The main types of ACE
In Russian power grids, two types of devices are most often used - PF 451 and PF 431. To select the desired model, the user must be aware of the differences between them.
Pf 431
Protects household appliances from voltage surges. Suitable for home use, including the owners of refrigerators that consume more than 1.5 kW per day, video surveillance systems and other equipment that functions for a long time every day and consumes a lot of power. The device monitors the potential difference at the output. A three-phase voltage is placed at the input, one phase at 220 V at a frequency of 50 Hz is output.
Pf 451
Provides uninterrupted operation of a single-phase line. It differs from the previous one by the absence of the option to set the leading phase. It connects one of them whose voltage parameters are close to optimal.
Connecting a phase switching device is a good way to ensure a stable supply of power to industrial or household equipment. It also increases electrical safety by protecting the circuit from burnout.
