ATS (Automatic Transfer Switch)

An automatic transfer switch continuously monitors the mains voltage. When it is lost or goes out of limits, the ATS signals the generatorGlossary · Generators and solarGeneratorAn engine-driven alternator that produces electricity when the grid fails, often started automatically through an ATS. to start and, once the generator voltage has stabilised, transfers the load to it. When the mains returns, it switches back, usually after a time delay. A mechanical or electricalGlossary · Power qualityNoise (Electrical)Unwanted high-frequency disturbances on the supply voltage, e.g. from motors or power supplies, which UPS systems and line conditioners filter out. interlock ensures the two sources are never connected at the same time.

Between the outage and the transfer there are usually a few seconds while the generator starts. That is why, for sensitive loads, an ATS is combined with a UPS, which bridges this gap without interruption.

Practical tip: install the UPS downstream of the ATS and make sure it accepts the generator's frequency fluctuations.