Automatic Transfer Switch (ATS) plays a crucial role in power systems where a backup power source is required in case the primary source fails. It automatically switches the load from the primary source to the secondary source, maintaining power continuity for critical applications. In this article, we will discuss the wiring diagram of a 3-phase ATS in detail, covering various components and their connections.
What is a 3-Phase ATS?
A 3-phase ATS is a device that automatically transfers the electrical load from the primary power source to a secondary power source when there is a failure or outage. It is designed for use in three-phase electrical systems, which are commonly used in commercial and industrial applications. The ATS is a critical component of a backup power system, as it ensures uninterrupted power supply to critical loads.
Components of a 3-Phase ATS
A 3-phase ATS comprises several components, such as:
- Power sources – primary and secondary
- ATS controller
- Relays
- Power contactors
- Current transformers (CTs)
- Control switches and indicators
Primary and Secondary Power Sources
The primary power source is the normal electrical supply, while the secondary power source is the backup power source, commonly a generator. The ATS controller monitors the status of both power sources and initiates the transfer process when required.
ATS Controller
The ATS controller is the brain of the ATS, responsible for monitoring the power sources and controlling the switching process. It is usually a microprocessor-based device that can detect voltage, frequency, and phase sequence of the power sources. The controller also monitors the ATS components and provides alarms and status indications.
Relays
Relays are electrical switches that can be controlled by the ATS controller. They are used to switch the power sources and control the power contactors.
Power Contactors
Power contactors are heavy-duty electrical switches that can handle high current loads. They are used to switch the electrical load from one power source to another.
Current Transformers (CTs)
CTs are used to measure the current flowing through the electrical circuits. They are connected to the ATS controller and provide feedback on the load current.
Control Switches and Indicators
The control switches and indicators are used to operate and monitor the ATS. They include buttons, switches, lamps, and digital displays.
Wiring Diagram of a 3-Phase ATS
A typical wiring diagram of a 3-phase ATS is shown in the figure below:
| Component | Connection |
|---|---|
| Primary Power Source | Connect to L1, L2, and L3 terminals of the ATS |
| Secondary Power Source | Connect to terminals X1, X2, and X3 of the ATS |
| ATS Controller | Connect to terminals C1, C2, and C3 of the ATS |
| Relays | Connect to terminals R1, R2, and R3 of the ATS |
| Power Contactors | Connect to terminals Q1, Q2, and Q3 of the ATS |
| Current Transformers (CTs) | Connect to the CT terminals of the ATS controller |
| Control Switches and Indicators | Connect to the control panel of the ATS |
FAQs
What is the purpose of an ATS?
The purpose of an ATS is to automatically transfer the electrical load from the primary power source to a secondary power source in case of a power outage or failure.
What is a 3-phase electrical system?
A 3-phase electrical system is a type of electrical power transmission that uses three alternating currents of the same frequency but with a phase shift of 120 degrees between them.
What is the difference between a relay and a contactor?
A relay is a switch that is operated electronically, while a contactor is a heavy-duty mechanical switch used to switch high current loads. Relays are used to control contactors.
How does an ATS controller work?
An ATS controller works by monitoring the status of the power sources and the load, and controlling the switching process. It uses sensors and feedback devices to detect voltage, frequency, and phase sequence of the power sources, and provides alarms and status indications.
What is the role of CTs in an ATS?
CTs are used to measure the current flowing through the electrical circuits and provide feedback to the ATS controller. They help in monitoring the load and ensuring that the rated capacity of the ATS is not exceeded.
Conclusion
In this article, we have discussed the wiring diagram of a 3-phase ATS, covering various components and their connections. A 3-phase ATS is an essential device in power systems that require a backup power source in case of a power failure. It ensures uninterrupted power supply to critical loads, making it a critical component in many commercial and industrial applications.
