Automatic Transfer Switch (ATS)
An automatic transfer switch (ATS) circuit is often used to switch between two power sources. The primary power source is usually the utility grid or mains power, while the secondary power source is usually a backup generator or other power supply, such as a battery or other utility feed.
Block Diagram of Automatic Transfer Switch (ATS):
ATS changeover wiring video in steps
Major Components with their function of ATS Circuit are:
Main Supply Grid Contactor: This contactor controls thе connection bеtwееn electrical load and primary power source, which is typically utility grid.
Standby Generator Contactor: This contactor manages thе connection bеtwееn load and secondary power source, which is backup generator.
Timers (Grid Timer and Generator Timer): These timers are used to provide delay in the switching process to ensure a smooth transition bеtwееn power sources. The grid timer and generator timer are typically set to specific time delay for safe transition during changeover.
DPDT Relay: The DPDT relay is used to control the contactors, manage timing functions, and ensure a fail-safe operation.
2-Polе Breaker: This breaker acts as a disconnect switch to isolate the load from both power sources during maintenance or service.
Control Wiring: Control wiring consists of cables, wires, and terminal blocks that connect all the components and allow them to communicate and work together cohesively.
Operation of the ATS Circuit:
Here’s a general sequence of how the ATS circuit operates with these components:
ATS changeover Practical wiring & Testing
Normal Operation:
During normal operation, the load is supplied by the main supply grid.The main supply grid contactor is closed, allowing power to flow from the grid to the load.
Monitoring:
The control logic continuously monitors the primary power source (grid) and the backup power source (generator) to detect any issues, such as power loss or unacceptable voltage/frequency levels.
Transfer Decision:
When the control logic detects a problem with the primary power source (grid), it initiates the transfer process.
Transfer Sequence:
The DPDT relay is used to coordinate the transfer process, ensuring a controlled transition.
The grid timer introduces a delay, allowing time for the grid to stabilize after a momentary power loss (if applicable).
The main supply grid contactor opens, disconnecting the load from the grid.
The generator timer introduces a delay to ensure the generator is ready to assume the load.
The standby generator contactor closes, connecting the load to the generator.
The DPDT relay ensures that the load is always connected to one of the two sources, preventing both contactors from being closed simultaneously.
Power Transfer:
The load is now supplied by the standby generator, providing continuous power during the grid’s interruption.
Recovery:
Once the primary power source (grid) is stable and available again, the control logic initiates the transfer back to the grid.The generator timer may introduce a delay for the generator to stabilize before disconnection.The standby generator contactor opens.The grid timer ensures a controlled reconnection to the grid.The main supply grid contactor closes.
Return to Normal Operation:
The load is now powered by the main supply grid, and the system returns to normal operation.