AUTOMATIC TRANSFER SWITCH ATS 3 PHASE 125AMPS

An automatic transfer switch (ATS) is a device that automatically transfers a power supply from its primary source to a backup source when it senses a failure or outage in the primary source
 
A transfer switch is an electrical  that switches a load between two sources. Some transfer switches are manual, in that an operator effects the transfer by throwing a switch, while this is an automatic it triggers when it sense one of the sources has lost or gained power.
 
An Automatic Transfer Switch (ATS) is often installed where a backup generator is located, so that the generator may provide temporary electrical power if the  fails
in a home equipped with a backup generator and an ATS, when an electric utility outage occurs, the ATS will tell the backup generator to start. Once the ATS sees that the generator is ready to provide electric power, the ATS breaks the home's connection to the electric utility and connects the generator to the home's main electrical supply. The generator supplies power to the home's electric load, but is not connected to the electric utility lines. It is necessary to isolate the generator from the distribution system to protect the generator from overload in powering loads in the apartment and for safety, as utility workers expect the lines to be off
When utility power returns for a minimum time, the transfer switch will transfer the load back to utility power and command the generator to turn off, after another specified amount of "cool down" time with no load on the generator.
 

this ATS can be used with big or small generator and can be connected to shutdown small Gen but can not start a small gen when there is power outage, when it shutdown the Gen it will automatically changeover to utility supply when available as the device will sense it once there is utility power supply

it can also be operated manually, before you operate manually first Switch the deice to manual mode.

for a big gen that has the ability to kickstart a provision is also made it will send the signal needed to start the generator when needed but most small gen of 1-10kva don't have a sophisticated mechanism to do that, mostly the chock need  to be operated manually for the kick to work.

using an automatic changeover has a lot of benefits as you don't need to stress yourself to changeover . 

it saves cost  because the changing over is fast

it cant forget to chance over as human can take time or forget. 24/7 its active

it proves protection for your equipment

100amps full load capacity

highly durable and reliable