Hello dear readers! Today we will analyze the automatic transfer device (ATS), as well as consider how it works and why it is needed.

Previously, we considered what is . Let's remember.

ATS is a device that is a component of relay protection and automation systems, and serves to ensure uninterrupted power supply to consumers of electrical energy. It transfers power automatically from the main type power source to backup power in the absence of voltage at the active input as a result of an emergency or erroneous actions. The reverse action occurs automatically when the voltage supply is restored.

Automatic reserve input is installed for special consumers who, for various reasons, cannot be left without electricity. Loss of electricity can lead to significant financial losses and in some cases to death. For example, in hospitals during an operation, etc.

Classification

Devices are divided according to the principle of operation.

• Unilateral. The scheme contains two sections: power supply and reserve. The latter is connected when the main voltage is lost.
• Bilateral. Any of the lines can be both working and reserve.
• Recoverable ABPs. When the main power is restored, the previous circuit is automatically put into operation, and the backup circuit is turned off.
• No automatic recovery. Setting the operating mode with the main power source is done manually.

Requirements that an AVR must have

1. The speed of switching on to work in the shortest possible time after disconnecting the power from the main voltage source.
2. Reliability, inclusion in any conditions in the event of a power failure in case of any malfunctions on the supply line or in the event of a power transformer failure. The exception is the blocking of the ATS when an arc protection is triggered in order to reduce damage to the network from a short circuit.
3. Selectivity or selectivity, for example, the lack of response from a power dip as a result of the start-up of high-power equipment by the consumer.
4. Single action, preventing multiple activations of the equipment due to unresolved causes of a short circuit or other malfunction.

How AVR works and why it is needed

In the event of a voltage drop in one of the phases, as well as frequency changes or voltage drops, that is, when these parameters go beyond the specified limits of the main power circuit, the phase control relay opens the contactor contacts at the main input and closes the contacts of the backup input contactors. Then the switches are activated, the consumers are disconnected from the main power supply and connected to the backup one. Most ATS schemes tend to work on this principle.

When the current parameters in the main circuit are restored, the contacts of the contactor of the main circuit are closed with simultaneous opening of the contacts of the reserve contactor. As a rule, the circuits additionally have a blocking of the simultaneous operation of the coils.

With the help of ATS, you can prevent the simultaneous switching on of two lines at once (main and reserve). In circuits in which sectioning is applied, the automatic transfer device will block the inclusion of sectional "AB". If necessary, AVRs are equipped with a special mechanical blocking system.

These devices can be installed in separate cabinets. Depending on the power consumption, they can be: small-sized, full-sized, two and three sectional. Also, ATS can be placed in distribution and introductory cabinets.

How does the ABP know it needs to work?

Automatic input of backup power is a full-fledged mechanism with its own logic and its own senses and controls. Which actually understand the situation, and make the only right decision to trigger the mechanism.

The reserve voltage input device usually includes a number of relays. They are connected to the section of the circuit that needs to be protected. The understanding device includes the phase control relay, it monitors the full-phase operation of the electrical installation. The voltage relay is also important, it serves to protect your equipment by turning off the electricity if its parameters differ from the frames set in it.

Simply put, if the voltage in your outlet deviates greatly from two hundred and twenty volts, the relay will simply turn off the contact and break the circuit. After that, a signal will be sent to another part of the circuit, and the backup input will turn on.

A simple scheme and principle of operation of ATS

In low-voltage networks, it is convenient to use special relays that control voltage in protection circuits. ATS is preferable here, since not all equipment is able to withstand frequent switching of power supply. This device is clearly visible in a simple diagram.

• Relay EL-11 controls the three-phase voltage, monitors the phase imbalance, their breakage and alternation.
• Electromagnetic relays with powerful contacts are used to connect loads. In normal mode, the magnetic starter coil of the main input is powered by it and with its contacts KM 1 connects the power supply to the load.
• When the voltage in the main circuit disappears, the KM 1 relay is turned off, and power is supplied to the coil of the KM 2 relay, which connects the backup input.

This ATS scheme can be used in private houses, industrial and administrative buildings, where the switched load reaches tens of kilowatts.

Also, it should be remembered that petrol or diesel generators are indispensable sources of additional power. The latter have found wide application due to their economy and greater power.

The principle of operation of the ATS and the generator

With frequent power failures in the network, it is better to install a reserve in the house, since the durability of household appliances depends on this, as well as comfortable living conditions. Uninterruptible batteries are installed in apartments, which are mainly used for electronic equipment. Generators are most common as backup power sources for private homes.

The generator in the simplest version is connected to the power supply of the house through a changeover switch. This prevents a short circuit in the event of an erroneous input of the reserve, when the automatic power supplies to the house are not turned off. The switch is selected with three positions, where the middle of them completely cuts off electricity.

ATS can be installed in automatic mode if the generator is equipped with an automatic starter and controlled from the cabinet using contactors that also switch inputs.

Automation works on microprocessor control, for example, on Easy relay controllers. Voltage sensors are used to enter the ATS reserve. As soon as the power is turned off, the generator engine starts immediately. It takes some time to reach the operating mode, after which the ATS switches the load to the reserve. Such delays are acceptable for domestic needs.

Block of automatic start of the generator (BASG)

The automatic generator start unit is a system that provides start-up and control of a standby generator in case of a power failure. It makes five attempts to start within 5 seconds in each interval after the voltage on the main input disappears. In addition, it controls the air damper, closing it at the time of launch.

If voltage appears again on the main input, the device switches the load back and stops the generator engine. When the generator is idle, the fuel supply is blocked by a solenoid valve.