Eaton ATC-900 Operation And Maintenance Manual - page 22
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IB140064EN
Instructional Booklet
Page 22
Effective: April 2018
Operation and Maintenance Manual, Automatic Transfer Switch, Bypass Isolation,
Contactor Type, Open/Closed Transition, ATC-900 Controller, 3000A Frame
5.4 Maintenance Isolation Switch (MIS)
The MIS is a 2-position, maintained contact switch marked "NOR-
MAL OPERATION" and "MAINTENANCE" (see Figure 29). When
the switch is turned to the Maintenance position, the compart-
ment power is switched off. Examples of compartment power are
sense lines to the controller, power to the transformer, genertor
starts, and controller contactor control power. The MIS is placed
in the "Normal Operation" position for normal ATS and Bypass
operation. The voltage to the stabs in the rear of the switch are
still powered when the MIS switch is used. If a meter is incorpo-
rated, the CT lines to the DCT module or other meter will still be
connected (with power). There is a Terminal Block (TBMS) avail-
able that will house a N.C. contact from the MIS switch that can
be used as a contact to show the position of the MIS switch.
Figure 29. Maintenance Isolation Switch.
5.5 Automatic Operation
The intelligence/supervisory circuits on Eaton transfer switches
constantly monitor the condition of both the Source 1 and Source
2 power sources. These circuits automatically initiate an immedi-
ate transfer of power from the Source 1 to the Source 2 power
source when the power source fails or the voltage level drops
below a preset value. Transfer back to the Source 1 power source
is automatic upon return of the Source 1 power source. Monitor-
ing the power source is always performed on the line side of the
power source to which the switch is connected. The Source 1
power source is usually the preferred source and the transfer
switch will always seek this source when it is available and when
it is selected in the ATC-900.
The intelligence/supervisory circuits will continue to function no
matter what contactor is being utilized: the ATS (#1) or the
Bypass (#2). This patented feature allows for a redundant auto-
matic switch.
5.6 Transfer to the ATS or the Bypass
As mentioned previously, the contactors in the switch are identi-
cal. Each can be in automatic (using the ATC-900), isolated for
testing, or the Manual mode operation. Each contactor may be
removed while the remaining contactor still remains as an auto-
matic (using the ATC-900), isolated for testing, or in Manual
mode. The Operating Panel shown in Figure 24 is all that is
required to control the different modes of operation. The following
are the modes of operations and instructions. The ATS (#1) or the
Bypass (#2) are shown on the operating panel are marked with the
left top side being the ATS and the right top side being the
Bypass. The three modes are:
1. Automatic operation using the controller.
2. Non-Automatic electrical operation using the user three posi-
tion Source Select switch.
3. Manual operation, non-electrical using the paddles and trip
button on the front of the contactor.
The ATS or the Bypass can be isolated for testing or removed
while the other contactor is on the automatic or non-automatic
state.
5.6.1 Automatic (Normal) Operation
1. All doors must be closed and latched. The Door Open light
should not be flashing.
2. Turn the 4 position Operation switch to the desired position
for Automatic Operation. The Green lamp will illuminate once
the contactor is in position.
NOTICE
IF A TRANSFER SWITCH WITH ANY TYPE OF ELECTRICAL OPERAT-
ING CAPABILITIES IS TO BE OPERATED MANUALLY UTILIZING THE
MANUAL PADDLE, IT IS STRONGLY RECOMMENDED THAT THE
TRANSFER CONTROL CIRCUIT FIRST BE ISOLATED. IN THE CASE OF
THE ATS DESIGN, ANY ATTEMPT TO OPERATE IN MANUAL WITH-
OUT FIRST ISOLATING THE CONTROL CIRCUIT CAUSES AN AUTO-
MATIC TRANSFER.
WARNING
THE VOLTAGE TO THE STABS IN BACK OF THE TRANSFER SWITCH
ARE STILL POWERED WHEN THE MIS SWITCH IS USED. IF A METER
IS INCORPORATED, THE CT LINES TO THE DCT MODULE OR OTHER
METERS WILL STILL BE CONNECTED AND HAVE POWER. APPROPRI-
ATE PPE SHOULD BE USED.
WARNING
THE CLOSED TRANSITION PRODUCT CONTAINS A SPECIAL
CONTACT ARRANGEMENT (OVERLAPPING CONTACTS). MISUSE
CAN RESULT IN DEATH, SEVERE PERSONAL INJURY, AND/OR
PROPERTY.