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    How Does Automatic Transfer Switch Work?

    The ATS, or automatic transfer switches, are basically the go-between utility power and generator power. There is a common load fed from the transfer switch usually to all your emergency panels. During a test or an actual power failure, there is a time delay before the ATS sends a signal to your generator, starting it. When the voltage and frequency of your generator is acceptable by the voltage sensing network, it sends a signal over to the mechanism. It will open up normal power and then close the generator. Now you're online and everything is stable at this point. When normal power, or utility comes back online there is a time delay preventing the generator from switching back- just in case normal power is unstable for a while.

    After 10 minutes of voltage sensing in your digital display is acceptable for utility it will send a signal to the mechanisms once again. It will open generator first, close normal power, and now you’re back on utility. The generator will cool down for a certain amount of time and then you’re ready for the next power failure. The automatic transfer switch is the heart of emergency power. Your generator has to be in good shape for the transfer switch to accept the power and it also has to be up to snuff for utility to be accepted by the power-but nothing happens without it.

    This is ATO automatic transfer switch (ATS). We are going to use this ATO single-phase to three-phase converter to power ATS.


    Wire according to the schematic. In manual mode, turn on normal power (main power) to power the load.

    ATS schematic

    Switch to automatic mode. We can see that the normal power and reserve power (backup power) indicators are on. Currently using normal power. When the normal power is disconnected the ATS automatically switches to reserve power. Reserve power output indicator is on. When normal power is restored, ATS automatically switches back to normal power. Switch to normal mode. When the normal power is cut off, the load loses power. Manually switch to reserve power and the load resumes operation.

    ATS automatic mode

    Switch back to automatic mode. After the normal power is restored, the ATS automatically switches back to the normal power mode.

    Back to automatic mode.

    If you want to learn more about automatic transfer switch, please click this video or contact us.

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