ATS

How does an automatic transfer switch work?
An automatic transfer switch (ATS) is a self-acting, intelligent power switching device governed by dedicated control logic. The principal purpose of an ATS is to ensure the continuous delivery of electrical power from one of two power sources to a connected load circuit (electrical equipment – lights, motors, computers, etc.).
AMF (Automatic Mains Failure)
The control logic or automatic controller is typically microprocessor-based and constantly monitors the electrical parameters (voltage, frequency) of primary and alternate power sources. Upon failure of the connected power source, the ATS will automatically transfer (switch) the load circuit to the other power source (if it is available). As a general rule, most automatic transfer switches seek connection to the primary power source (utility) by default and will only connect to the alternate power source (engine-generator, backup utility) when required (primary source failure) or requested to do so (operator command).
A typical transfer sequence includes:
1. The normal utility power source fails.
2. The transfer switch shifts the load to the emergency power source when power from the generator or backup utility feed is stable and within prescribed voltage and frequency tolerances. Depending on a facility’s needs and preferences, the transfer process is self-acting or manually-initiated.
3. The transfer switch returns the load from the emergency power source to the normal power source when utility power is restored. The retransfer process is self-acting or manually-initiated.