Transfer switch
The transfer switch allows switching from a primary power source to a secondary or tertiary power source. Transfer switches are employed in some electrical power distribution systems. Most often transfer switches can be seen where emergency power generators are used to back up power from the utility source. The transfer switch allows switching from utility power to emergency generator power. The switch is either a manual switch, an automatic switch or a combination of manual and automatic. During a power outage, the transfer switches isolate the emergency circuits from the utility line allowing for efficient operation of the generator without back feeding onto the utility.
Break Before Make Transfer Switch
A Break Before Make transfer switch breaks contact with one source of power before it makes contact with another. It prevents backfeeding from an emergency generator back into the utility line. One example is an open transition Automatic Transfer Switch (ATS). During the split second of the power transfer the flow of electricity is interrupted.
Closed Transition Transfer Switch (CTTS)
Provides seamless transfer switching in less than 1/2 cycle.
Soft-loading Transfer Switch (SLTS)
An SLTS essentially uses CTTS technology but actively changes the amount of load accepted by the generator.