Description Of Operation; Definitions - Eaton Cutler-Hammer MP1 Series Instructions Manual

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3.3 Description of Operation

The Cutler-Hammer Automatic Transfer
Switch provides automatic transfer of an
electrical load to a standby power supply in
the event of drop or loss of voltage of any or
all phases of the normal power supply. Upon
the restoration of the normal supply, the
electrical load is automatically retransferred
to the normal power supply. The mechanism
provides a positive mechanical interlock to
prevent both breakers being closed at the
same time. The mechanism is also designed
to leave both breakers trip free in the closed
position, permitting incorporation of thermal
and short-circuit protection in either or both
breakers. In Type B switches, an alarm
switch contact is supplied. This contact is
connected to the controller to lock the motor
circuit out of operation when the breaker(s)
trip on an overload or short-circuit condition.
Then the breaker has to be manually reset.
Instructions for the reset procedure are
located on the front of the operating
mechanism.

3.4 Definitions

With respect to their use in this document
and as they relate to automatic transfer
switch operation, the following terminology is
defined:
Available – A source is defined as
"available" when it is within all undervoltage /
overvoltage / underfrequency /
overfrequency setpoint ranges for the
nominal voltage and frequency setting.
Fails – A source is defined as "failed" when
it is outside of any undervoltage /
overvoltage / underfrequency /
overfrequency setpoint ranges for the
nominal voltage and frequency setting for a
time exceeding 0.5 seconds.
Failsafe – Refers to the condition whereby
the transfer switch is connected to the
emergency source. In the event that the
emergency source fails with normal source
available an immediate retransfer to normal
source shall occur.
Transfer – A "transfer" is defined as the
automatic operation under a normal source
failure of switching the Load from Normal
Source to the Emergency Source.
Retransfer – A "retransfer" is defined as the
automatic operation under Normal Source
reappearance of switching the Load from
Emergency Source to Normal Source.
I.L.15.01.T.K
.
Effective June 2000