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emergency power source when sufficient generator volt-
age is available. When normal power is restored, the
transfer switch automatically transfers back and initiates
engine shutdown. In the event the normal power source
fails and the emergency power source does not appear,
the automatic transfer switch remains connected to the
normal power source until the emergency power source
does appear. Conversely, if connected to the emer-
gency power source and the emergency power source
fails while the normal power source is still unavailable,
the automatic transfer switch remains connected to the
emergency power source.
1.2.1 TRANSFER SWITCH TYPES
In general, there are four types of basic transfer switch
equipment:
Automatic Transfer Switch
Automatic transfer switches automatically perform the
transfer function. They consist of three basic elements:
(1) Main contacts to connect and disconnect the load
to and from the source of power.
(2) Intelligence/supervisory circuits to constantly moni-
tor the condition of the power sources and thus pro-
vide the intelligence necessary for the switch and
related circuit operation.
Normal
Source
Figure 1-1 Typical Load Transfer Switch (circuit break-
er type) Schematic
Emergency
Source
Load
(3) A transfer mechanism to effect the transfer of the
main contacts from source to source.
Basic Transfer Switch
The basic transfer switch is designed for use with cus-
tomer furnished logic. It is similar in design to the auto-
matic version except the intelligence circuit (logic panel)
and voltage selection panel are omitted. All automatic
sensing devices, relays or solid state devices are the
customer's responsibility.
Non-Automatic Transfer Switch (Manually Operated)
Non-Automatic transfer switches provide the main con-
tacts and the transfer mechanism to effect the transfer
of the main contacts from source to source. Transfer of
power, however, is accomplished by true hand opera-
tion (not power assisted) of the transfer switch. This
switch is similar to the basic switch in that an intelli-
gence circuit and a motor driven mechanism are not
part of the design.
Non-Automatic Transfer Switch (Electrically
Operated)
This transfer switch is similar to the Non-Automatic
Transfer Switch (Manually Operated) just described
except that an electrical operation feature is added. The
switch electrically transfers power when an appropriate
pushbutton on the front of the enclosure is pushed. If
necessary, the switch can also be operated manually.
The automatic transfer switch, basic transfer switch and
non-automatic transfer switch (electrically operated) are
the available types for the configuration described in this
manual. Operation of the automatic transfer switch only
is discussed in detail (Section 5).
1.2.2 DESIGN CONFIGURATION
The Cutler-Hammer transfer switch is a rugged, compact
design utilizing insulated case switches or insulated case
circuit breakers to transfer essential loads from one
power source to another (Figures 1-2 and 1-3). The ver-
satile design, in addition to standard transfer functions,
offers an optional integral thermal and short circuit protec-
tion in either or both switching devices.
The switching devices are in a compact vertical arrange-
ment. The logic can be easily disconnected from the
switching device without disturbing critical connections.
The enclosure is free standing, and, by using the special-
ly supplied cleats, the switch is seismic approved (Option
42). The terminals are mounted in the rear of the switch,
permitting rear, top, bottom or side cable or bus bar
entrance.
I.B. ATS-CP01
Effective 5/98
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