When the generator is operating, the transfer switch prevents dangerous feedback of current to the utility system. It also ensures that different power sources are fully synchronized before their power is combined or loads are transferred, which is imperative for safe operation.
The transfer switch senses when utility power is interrupted, and starts up the generator if the utility power remains absent. In about five to ten seconds, when the generator is producing full power, the transfer switch disconnects the load from the utility and connects it to the generator, restoring electricity to the load. The transfer switch continues to monitor utility power, and when it is restored, switches the load from the generator back to the utility. Once the generator is disconnected, it goes through a cool-down routine and is automatically shut down.
Generac manufactures several types of transfer switches. Each kind operates in a different way, depending upon the requirements of the overall system, and how the load is transferred between the different power sources. Transfer switch types include open transition , momentary closed transition , and bypass isolation.
Generac's automatic transfer switches are designed to be simple to monitor, operate and maintain. All controls needed for daily use are conveniently located on the front door, where bright lamps indicate the switch position. All components are front adjustable and front removable for optimum serviceability. As an extra measure of safety and quality, Generac's transfer switches are UL Listed by Underwriters Laboratories for use in emergency power systems. They are also CSA certified by the Canadian Standards Association.
Generac's expertise in the design and manufacture of automatic transfer switches (ATS) is considerable. The company has produced its own fully instrumented 100 to 2600 amp switches since 1983.
Open transition transfer switches are the simplest kind, and are mechanically interlocked. They disconnect the load from one power source before making the connection to the other.
Generac's closed transition transfer switches (CTTS) eliminate momentary power interruption when both sources are present and synchronized, by transferring the loads with an overlapping contact arrangement. The momentary closed transition switch transfers the power within one hundred milliseconds, which does not require utility protective relaying.
The soft load closed transition switch extends the overlap time to multiple seconds, for a smoother transition of load to the generator. These switches are available in 100 to 2600 amp configurations.
There are many critical systems where interruption of power is not permitted, such as data transmission and hospital care. For those requirements, Generac offers its bypass isolation switch (BIS), which is designed to meet the National Electrical Code's requirements for the inspection and/or maintenance of the automatic transfer switch without the need to interrupt or cut power.
Generac transfer switches are carefully constructed and tested to assure superior performance. By combining them with our own generators, we're able to offer a complete power generation package that we support and warrant.