Transfer Switch Types; Design Configuration; Typical Load Transfer Switch (Circuit Breaker Type) Schematic - Eaton Cutler-Hammer O & M Manual

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those caused by power sources or equipment external
to the transfer switch. If both sources are acceptable as
determined by the IQ Transfer logic, a make-before-
break transfer is performed during a transfer test or
retransfer operation.

1.2.1 TRANSFER SWITCH TYPES

There are three types of 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.
(3) A transfer mechanism to effect the transfer of the
main contacts from source to source.
Basic Transfer Switch (Power Panel)
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 control
Normal
Source
Figure 1-1 Typical Load Transfer Switch (circuit break-
er type) Schematic
Emergency
Source
Load
devices are the customer's responsibility.
Non-Automatic Transfer Switch (Electrically
Operated)
Non-Automatic Transfer Switches are manually initiated,
electrically operated devices for applications where
automatic load transfer is not required.

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. Open Transition switching
devices are interlocked to prevent both switching devices
from being closed at the same time. The versatile design,
in addition to standard transfer functions, offers an option-
al integral thermal and short circuit protection 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.
The switching devices have a high withstand
rating (Table 1.1). The high-speed, stored-energy switch-
ing mechanism guarantees a transfer time of
less than 5 cycles.
IB01602002E
Effective 10/02