Product Manual

TP-6946 3/16 9Section 1 Product Description
Section 1 Product Description
1.1 General Description
An automatic transfer switch (ATS) transfers electrical
loads from a normal (preferred) source of electrical
power to an emergency (standby) source when the
normal source falls outside the acceptable electrical
parameters. Figure 1-1 shows a typical single-line
diagram. Figure 1-2 shows a typical transfer switch.
Model KEP automatic transfer switches employ two
mechanically interlocked enclosed contact power
switching units and the Kohlerr Decision-Makerr
MPAC 1500 controller to automatically transfer system
load to a generator supply in the event of a utility supply
failure. System load is then automatically retransferred
back to the utility supply following restoration of the utility
power source to within normal operating limits.
Model KEP service entrance rated transfer switches
have integral overcurrent protection supplied on the
utility source as standard, which allows installation at the
point of service entrance and eliminates the need to
have a separate upstream utility source circuit breaker
or disconnect switch. Integral overcurrent protection
can also be selected on the generator source. Refer to
Section 1.2, Overcurrent Protection, for more
information on overcurrent protection.
The Model KEP service-entrance rated automatic
transfer switch uses integral overcurrent protection
within the enclosed contact power switching units. The
100--1200 A rated molded case power switching
devices used for the utility and generator sources are
operated by an electrically driven motor mechanism in
the transfer switch. The 800--4000 A rated insulated
case power switching devices used for the utility and
generator sources are operated by internal drive motor
operators.
CUSTOMER
LOAD
N
N
N
UTILITY SUPPLY
REMOVABLE
NEUTRAL
GROUND
BOND
CONDUCTOR
STANDBY GENERATOR SET
GENERATOR
CIRCUIT
BREAKER
GCB
GENERATOR
POWER
SWITCHING
DEVICE
(NON-AUTO)
MECHANICAL
INTERLOCK
UCB UTILITY
POWER
SWITCHING
DEVICE
W/TRIP UNIT
SERVICE ENTRANCE
AUTOMATIC TRANSFER SWITCH
3-POLE MODEL SHOWN
Figure 1-1 Typical Single-Line Diagram
The transfer switch mechanism provides a positive
mechanical interlock to prevent both power switching
units from being closed at the same time, allowing an
interrupted open-transition break-before-make transfer
sequence. The transfer switch controller provides a
standard neutral position delay timer for
programmed-transition transfer sequences to allow
adequate voltage decay during transfer operation to
prevent out of phase transfers.
Note: For the purpose of this manual, the following
nomenclature is utilized:
D Utility or Normal to indicate the source of
primary power.
D Generator or Emergency to indicate the source
of standby power.
D Power switching device to indicate the
automatic transfer switch power switching
device [molded case (MC) or insulated case
(IC) circuit breaker (CB) or switch (SW) in the
ATS].
g11--133
Figure 1-2 Model KEP Service Entrance ATS
(ICCB type shown)