No source of electricity can be considered completely reliable, and there is always a risk of disconnection from the network. In such a situation, the consumer can have serious problems. If important devices are connected to the mains, then such a disconnection should not be allowed. It is to solve this problem that the ATS circuit for 2 inputs or more is used. As a result, when the main source of energy is lost, the backup one is automatically connected.
Content
- Application area
- Principle of operation
-
Simple schemes
- Contactor based
- On a reversible switch
Application area
First, it is necessary to say about the decoding of the automatic transfer switch - automatic input of the reserve. These systems are mandatory used in the power grids of consumers of the first category. They are necessary to ensure that power outages do not lead to serious financial losses or a threat to human life.
ATS systems are usually classified according to the principle of operation:
- Unilateral - the circuit includes sections of the main and backup power supply.
- Double-sided - each line can be used as a backup or main.
- Recovering - after the restoration of the main power supply, the system goes into the previous mode of operation.
- Non-recoverable - disconnection of the backup power system is done manually.
The automatic transfer system can be used not only in industry, but also in private houses. With some knowledge in electrical engineering, you can assemble a simple circuit with your own hands. However, it is worth examining the ATS device first.
Principle of operation
If the voltage drops on one of the phases or the frequency changes, the relay disconnects the contactor at the main input and closes the contacts of the second device installed at the backup input. This disconnects the main power supply and connects to the backup power supply. Most automatic input systems work on this principle.
As soon as the set parameters are restored in the main circuit, the system goes into normal operation. Most often, an additional blocking is provided in the ATS circuit against the simultaneous operation of the relay coils. This allows you to avoid connecting the consumer to two power grids at once (main and backup). It should be understood that ATS is a complete system with its own logic and controls.
Simple schemes
If the owner of a private house wants to avoid power outages, then he can independently assemble a simple ATS circuit. They contain a minimal number of elements and are quite reliable.
Contactor based
The simplest is the circuit ATS on contactors, which is designed for single-phase networks.
The principle of its operation is quite simple: SA 1, SA 2 are switched on in turn. If there is voltage in the main power grid (input 1), then it will supply the load. Thus, input 2 is a redundant power supply. As soon as the mains voltage is lost, it is automatically switched to input 2.
In this mode, the system will work until the power supply is restored at input 1. The described circuit is highly reliable and can function effectively even without mechanical interlocking of the starters. Moreover, such an improvement is excessive.
To start one of the inputs, a short-term voltage cut-off using the SA 1 or SA 2 circuit breakers is sufficient. The logic of the system is simple and does not require a detailed description. One has only to remember that the closing terminals of the contactors must be selected according to the indicator of the total load current. There are no specific requirements for NC contacts, since they are used as auxiliary contacts.
On a reversible switch
This design is of interest in that it is capable of consuming electricity exclusively at the moment of switching. In this, it differs significantly from the circuit on the contactors. It is based on an automatic disconnector such as the NH40SZ. This device is capable of operating in the mode of a network power source and provides automatic switching between inputs.
In addition, the device offers three modes of operation as the main power source, while performing the following functions:
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Switching to the main input in automatic mode with testing the functionality of the lost phase. - Self-resetting with simultaneous undervoltage and overvoltage testing.
- When returning to operation from main power, undervoltage, frequency and overvoltage checks are performed.
A generator is most often used as a backup power source in a private house. The simplest option for switching from the main power grid to the backup one is to install a three-position switch. Equipping the generator with an automatic starting device, you can get the simplest ATS circuit.
