Specifications

Distribution Products Catalog CA08101001E—October 2010 www.eaton.com 7
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16.1
Tr a n s f er Switches
Tr a n s f er Switch Equipment
Utility—Generator
Transfer switches are
traditionally applied between
a utility and a generator set
for emergency and standby
power systems.
Generator—Generator
Transfer switches are
sometimes applied between
two generator sets for
prime power use, often
in remote installations. In
such applications, source
power is periodically
alternated between the
generator sets to equally
share run time.
Service Entrance Rated
Transfer Switches
Modifying the molded
case switch in the transfer
switch by adding trip units
and optional ground fault,
along with adding the service
entrance option eliminates
the need for separate
upstream disconnect devices
and their respective power
interconnections. This means
the automatic transfer switch
(ATS) is installed directly
at the point of service
entrance, saving valuable
space and cost.
Built-In Protection
All Eaton molded case
switches are “self
protected,” such that under
extreme fault conditions,
the switch will open before
destroying itself. This
feature allows Eaton to
offer “Maintenance-Free
Contacts” on the molded
case transfer switch. The
molded case switches have
instantaneous magnetic
trip units installed in each
switch. These trips are not
accessible once installed by
the factory to eliminate field
tapering. The trips are set to
a minimum of 12 to 15 times
the rated current of the
molded case device, well
above any coordination set
points. This means they will
not interfere with the normal
operation of the distribution
system and will only trip if
something is very wrong.
Standard Application Utility—Generator
Standard Application Generator—Generator
Service Entrance Rated Transfer Switches
Built-In Protection
Note

Magnetic Trip 12 x frame rating.
Se
rvi
ce
Disconnec
t
Utilit
y
G
Ge
n
e
r
ator
Breake
r
L
oad
AT
S
G
Ge
n
e
r
ator
Br
ea
k
er
G
Ge
n
e
r
ator
Br
ea
k
er
L
oad
AT
S
Generator
Breaker
G
Load
Service
Disconnect
ATS
Utility Service
G
Generator
Breaker
Load
ATS
Service
Disconnect
Utility Service
Typical Transfer Switch Installation
Transfer Switch Installation Rated
For Service Entrance
400 FLA x 1.25 = 500 Ampere Breaker
Compare 400 Ampere ATS and 500 Ampere LD Breaker
Time
(Min.)
5
1 2 3 4 5 6 7 8 9 10
Breaker Ok
400 ATS
햲
Will Only Trip at
7200 Amperes 100% Rated
Device per UL 1008
Breaker Trips
ATS Ok
ATS Trips
500 Ampere
HLD Breaker
Current x 1000
Misconception: Breaker
Type Switches Susceptible
to Nuisance Tripping.
Example: 400 Ampere ATS With 500 Ampere T/M Breaker
Reality: Upstream Breaker
Will Trip Before ATS MCS
Trips When Overcurrent
is <7200 A