3 Phase ATS(Automatic Transfer Switch) Wiring Diagram and Connection

In this article, we are going to see the 3 Phase ATS(Automatic Transfer Switch) Wiring Diagram and Connection Procedure.

A Three Phase Automatic Transfer Switch (ATS) is a device that automatically transfers electrical power supply between two or more three-phase sources in the event of a power outage or when the primary source fails. It is commonly used in commercial, industrial, and large-scale applications where three-phase power distribution is required.

Three-phase power systems use three alternating current (AC) voltages that are 120 degrees out of phase with each other. This type of power distribution is more efficient and is commonly used in larger buildings, industrial machinery, data centers, and other power-hungry applications.

Wiring Diagram

Here, you can see the wiring diagram of a 3 Phase ATS(Automatic Transfer Switch) where the Utility Supply is used as the main power supply and a Generator is used for the backup power supply.

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Connection Procedure

1. Before making the connection, identify the input and output terminals of all the devices. Read the user manual from the manufacturer if required.

2. The output of the three-phase energy meter is to be connected to the source 1 terminals of the Transfer Switch through an MCCB.

**Remember that here, we have used a 3-phase four-wire transfer switch, but the 3-phase 3 wire transfer switch is also available in the market. When you use the 3-phase 3 wire transfer switch, the neutral should be connected directly and only the phases should go through the switch. It is recommended to use 3 phase 4 wire switch if you using neutral also**

3. The output from the generator is to be connected to the source 2 terminals of the Transfer Switch through an MCCB.

4. Now connect both the outputs of the Transfer switch together and then connect to the input of the three-phase Distribution board or load you want to connect.

5. The backup generator can be configured as manual or automatic. In the manual configuration, we have to turn on the generator manually when the utility power fails. In the automatic configuration, the generator will automatically turn on when the utility power supply fails. It may need an additional connection. So follow the instructions provided by the manufacturer.

Working Principle

Similar to the Single Phase ATS, the core component of the Three Phase ATS is the switching mechanism. It enables the transfer of power from the primary (utility) source to the secondary (backup generator or another power source) and back again automatically when needed.

The controller in a Three Phase ATS is more complex than the single-phase switch. It monitors the three-phase power sources continuously and triggers the switching process when it detects an outage or abnormal conditions in the primary power source. It also ensures a synchronized transfer between all three phases.

The sensing devices, such as voltage and frequency monitors are used for each phase and they are crucial in determining the status of the primary and secondary power sources, ensuring a stable and seamless transfer.

Just like in the Single Phase ATS, the transfer time is an important parameter in a Three Phase ATS as well. It is essential to keep the transfer time as low as possible to prevent disruptions to sensitive equipment during power transitions.

In some advanced ATS systems, a bypass switch might be included. The bypass switch allows manual or automatic bypass of the ATS, enabling maintenance or repairs without interrupting the power supply to the critical loads.

Three Phase ATS systems are more complex, costly, and capable of handling higher power loads compared to single-phase ATS systems. They are essential in situations where continuous power supply is critical, and downtime due to power outages is not acceptable. These ATS systems are often used in conjunction with backup generators or alternate power sources to ensure the uninterrupted operation of various industrial processes and critical infrastructure.

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