Automatic Transfer Switch (ATS)

What is meant by Automatic Transfer Switch (ATS)?

Automatic Transfer Switch (ATS) is a device which automatically switches the load between two sources using the controller and relays. In most cases, ATS’s are used to connect the load to the generator power automatically, when there is a utility outage. It also retransfers the load to utility automatically, once utility power is back and healthy. Nowadays, ATS plays a vital role to maintain the loads in the datacentre and health infrastructure systems.

 

Why Automatic Transfer Switch (ATS) is required?

• Provides emergency back-up power
• No manual intervention is required
• Improves system reliability
• Automatic sensing of source failure and restoring when power comes back.
• Preferred source selection can be achieved
• Easy maintenance

 

Who manufactures ATS?

Some ATS Global Manufacturers are listed below.

GE/Zenith, ASCO, Russelectric, Schneider, ABB, Eaton

 

How does ATS function / operate?

Utility power is sensed by controller and when there is an outage, the controller senses the power failure and the engine start relay will send the start signal to the generator. Once generator reaches its rated voltage and frequency, loads will be transferred to generator.

 

When utility returns back, controller senses the utility power and start signal to the generator will be removed. Now the loads will be re-transferred back to utility. Generator will go shutoff after Cool down time (CDT).

Let’s have a look on the below image sequences and learn how ATS works.

 

Generator start signal will be sent only if AUMS (Auto/Manual) Switch is placed in “Auto” position. If AUMS is placed in “Manual”, automatic operations are prohibited. Manual intervention will be required to start/stop the generator.