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IB140042EN
For more information visit: www.eaton.com
Instructional Booklet
Effective: May 2015
Page
29
ATC-300/900 Breaker Based Transfer Switch
Figure 33. Indicator Wheel in Neutral Position (225-1200 A
Models).
The three distinct switch positions or contact conditions are:
Source 1:
The contacts associated with the Source 1 power
source are closed and the Source 2 power source con-
tacts are open.
Neutral:
The contacts associated with both the Source 1 and
Source 2 power sources are open. This position allows
for load circuit maintenance.
Source 2:
The contacts associated with the Source 1 power
source are open and the Source 2 power source con-
tacts are closed.
To manually operate the ATS, the manual operating handle is
ratcheted until the desired switch position is indicated on the indi-
cator wheel. The operating handle, no matter what design or type
of switch operation, is always electrically "dead" and the indicator
wheel free-wheels should a particular switch have a motor and be
capable of electrical operation. This feature ensures no operator
problems should the switch automatically operate while the man-
ual handle is being used.
5.3 Manual Operation (30 - 150 A)
To operate the breaker manually, or if the breaker trips, unplug P3
from S3 to disconnect the motor circuit (Figure 35). Turn and
hold the break release lever to “HOLD FOR MANUAL OPERATION”
position, and then rotate the manual operator knob in either direc-
tion to move the ATS into the desired position. Let go of the
brake release lever for “AUTOMATIC OPERATION” after P3 and
S3 are reconnected.
Figure 34. Switch Being Manually Operated (30-150 A Model).
5.4 Automatic Transfer
The operating sequence of an ATS is dictated by the switch's
standard features and selected options. Operation of an ATS dur-
ing Source 1 power source failure and Source 1 power source res-
toration will be described here with only standard options included
on the switch. Additional options, as described in Section 3, can
change sequences and timing, depending upon the options
selected. It is strongly suggested that you become familiar with
additional options selected with the particular ATS and their effect
on the normal operation of an ATS.
5.4.1 Source 1 Power Source Failure
Standard Source 1 power source failure is defined as a reduction
or loss of voltage. If this occurs, the sequence of operation is as
follows.
1. Failure of Source 1 is detected by the controller intelligence.
2. When the controller detects a failure, the engine contacts
close (after delay if programmed) and start the engine-driven
generator.
3. When the Source 2 voltage reaches its operation rating, the
K2 relay closes, starting the transfer operation. This operat-
ing sequence opens the Source 1 switch and closes the
Source 2 switch.
4. The load is now transferred to the Source 2 power source.
5.4.2 Source 1 Power Source Restoration
1. A return to the Source 1 power source begins when the volt-
age in all phases of a three-phase sensing unit, or phase-to-
phase in a single sensing unit, is restored to a preset value.
2. At the present voltage, the controller will cause the K1 relay
to change state. This starts the return to the Source 1 power
source and Source 1 transfer switch operation.
3. During this sequence, the Source 2 power source switch is
opened and the Source 1 power source switch is closed.
4. Simultaneously, the engine cool-down timer initiates the shut
down of the engine driven generator.
5. Transfer of the load back to the Source 1 power source is
now complete.