Why do I need a phase switch and where is it used?
Device and principle of operation
A phase switch is a device that instead of the main phase connects any other in which the voltage is closer to normal when the main power disappears or goes beyond the set limits. If you still do not understand what this device is for, let's take a closer look.
From the definition it follows that three-phase power is supplied to the input terminals of the phase switch, and one exits from it, the voltage quality of which is closest to normal. Switching itself occurs during jumps, drawdowns or the complete disappearance of the main one. The choice of the main line is carried out depending on the specific option. From here follows a restriction - the phase switch should work in a three-phase network. It can be used for a generator, but then, you need to think about how to generate a control pulse to start it. The device can be manual and automatic.
The principle of operation is to sort through the lines, until the one with the optimal parameters is found by switching the relay group by the microcontroller.
In addition to automatic phase switches, manual options are also common. The manual switch is a 3-position cam switch, sometimes called a “bag”. At the same time, there is a 2-position and 4-position switch on sale, depending on the needs of the consumer.
Low-power mechanical models of switches are needed not for switching the load, but for switching the line measured by a voltmeter. The switching order may differ, for example, 0-1-0-2-0-3, where 0 - all phases are disabled, and 1,2 and 3 are the number of the selected line. Powerful models are convenient to use to reverse the engine or connect the load, you can make switching under voltage.
Be careful the switch to 3 positions is not a fact that it will switch three phases, perhaps its position is 1-0-2, i.e. the first pair of contacts is closed, and the second pair of contacts is disconnected.Read the documentation for it and check the switching scheme; if there is no documentation, you can check it with the usual dialing.
How to choose a phase switch
We examined how the phase switch works, now let's find out what you need to look at when choosing automatic models. In addition to the power parameters, functions are added to the PF that simplify the setup and operation process.
First and foremost is current. So that the phase switch fits your power supply system, the main criterion that you need to look at when choosing is the permissible current. Do not buy a device whose current exceeds the rated current of the input machine. But selectivity of protection It should provide a safe mode of operation, but it will not be superfluous to bring the power supply into line with the allowable current and power.
The second parameter is possibility of adjustment. On cheap switches, it is generally not possible to set the value of the minimum and maximum voltage in the power supply network at which the switching occurs, the choice of the priority phase. The minimum set of adjustments is to set the minimum voltage at which the devices can operate, the maximum. In more advanced models, you can adjust the time after which you need to try to go to the main phase and other settings.
The third parameter is display and indication method. In simpler models, there is an LED indication, usually one LED per phase and an additional “ALARM” indicator. When the line is normal and the load is connected to it, the corresponding LED lights up, for example, in green, when the line is normal, but it is in standby - the LED blinks, when there is a problem along all lines - the ALARM indicator lights up. In more advanced models, a seven-segment indicator or LCD display is installed. The purpose of the indicators: display the voltage value, settings, on and priority phase. The least obvious way of indicating is individual LEDs, and the most obvious is the LCD.
The fourth parameter is functional. The simplest PF has a set of predefined parameters of the mains, taken as the norm, and seeks to adhere to them. But each electrical device requires an individual approach to power, usually it is 220 +/- 10% V, and in some cases the tolerance can be increased, or vice versa - reduced. In more advanced models, these values are set by turning the screws or handles in the desired position, according to the graduation. The most functional are models with a display and touch control. At the same time, you should not assume that the simpler - the worse, often you should not overpay money for functions that are not useful.
If the power of your switch is not enough to meet your needs, there are two ways to solve this problem:
- Buy a switch designed for more current.
- Install the electromechanical switch so that a coil is connected to the output terminals of the phase switch starter or contactor. Thus, the entire load will fall on the power contacts of the latter.
Application area
We repeat that before ordering a switch, you should know that it requires 3 phases to operate. Reserve lines are taken from additional phases. Between phases, the voltage is 380 volts, it is called "linear", and between phase and zero 220 volts, it is called "phase". They are interconnected, but within this article we will not delve into electrical engineering basics. The main thing is for you to understand that to connect to electrical networks, you need a three-phase network, namely 380 Volts.
As already mentioned, this device is used to connect a backup line. This only works if one of the phases of the transformer is overloaded or there is a skew.In cases when the transformer receives “bad” voltage, an automatic reserve input from another line is needed, the phase switch will not help in this situation.
The units with continuous operation are powered by a phase switch. I propose to consider the scope in illustrative examples.
In medicine:
- life support devices;
- drug refrigerators in pharmacies;
In production and in offices:
- automation tools;
- control and monitoring equipment that records signals;
- communication facilities, stationary radio stations, dispatching equipment;
- ventilation systems;
In home:
- gas boiler;
- security system;
- video monitoring;
- smart home system;
Wiring diagram
After the purchase, you may have difficulty with how to connect the phase switch. If you do not have experience with electricity, it is better not to try, since you will have to work with high voltage in a three-phase network - 380 Volts. In addition, improper use and connection of such equipment can lead to a short circuit between the phases.
The phase switch is a modular device that is installed in the shield on the object on din rail. A three-phase circuit breaker is installed in front of it. After installing the primary circuit, go to the weekend. But how to connect the secondary circuit depends on the model of switch. The connection diagram must be indicated in the technical passport or other similar documentation and may differ from manufacturer to manufacturer.
Finally, we recommend that you watch the video, which describes in more detail what the phase switch is and how to connect it in the dashboard:
Phase switch - a budget way to increase the stability of electricity supply, it can be especially important outside the city in a cottage, in a holiday village, where there are usually interruptions in electricity. We talked about how to connect and where to install, as well as about all the parameters of such devices. The choice of uninterrupted supply is up to you based on your needs and budget.
It will be useful to read:
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Can you explain the second connection diagram in the figure?