TP-5672 11/95
Specifications 1-1
Section 1. Specifications
Purpose of Switch
An automatic transfer switch (ATS) is a device used for
transferring critical electrical loads from a normal
(preferred) source of electrical power to an emergency
(standby) source. This transfer occurs automatically
when the normal source voltage fails, or is substantially
reduced, and the emergency source’s voltage has
reached an acceptable level.
Upon normal source failure, the automatic transfer
switch controller signals the generator set(s) to start and
transfer to the emergency source. The automatic
transfer switch controller continuously senses for an
acceptable normal source and will retransfer the load to
the normal source after it has been restored to an
acceptable level. After retransfer of the load, the
generator set start signal is removed and the generator
set(s) is allowed to shut down.
Components of Switch
A typical automatic transfer switch includes the actual
power switching device and the logic controller to
perform power monitoring and transfer sequencing
tasks. See Figure 1-1. An interface board is also
included to match the controller inputs/outputs to the
levels required by a specific switching device.
The three functional units that make up the automatic
transfer switch are mounted in an enclosure with a
hinged front door. The controller mounts on the back of
the front door so its controls and indicators are available
to an operator. A signal cable with in-line connectors to
facilitate component replacement and door removal
connects the controller to the interface board and the
switching devices.
1
2
3
567111
1. Power Conversion Unit
2. Interface Panel
3. Logic Controller
Figure 1-1. Transfer Switch Components
