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Instructional Booklet
Page 6 Effective: March 2021
Operation and Maintenance Manual,
Automatic Transfer Switch Controller, ATC-900
1.5 .4 How the ATC-9 0 0 evaluates Closed or In-phase transitions
The controller software will confirm that the Closed Transition
(CT) or In-phase transition is enabled through the set-points.
When Source 1 and Source 2 are both Available within voltage
and frequency set point tolerances:
• If S1 and S2 set points (UV/OV, UF/OF) are identical, there can
be a difference in voltage and/or frequency when transition
occurs. Also, if there is a difference in setpoints, the actual
voltage and/or frequency may be identical when the transition
occurs.
• It confirms that sources are within Closed or In-phase transi-
tions set point tolerances when:
– Voltage difference for Closed = +/- 1 to 5%,
– There is no voltage difference setpoint for in-phase. As
long as both voltages are with in voltage limits any differ-
ence in acceptable
– Freq. difference = +/- 0 to 0.3 Hz for closed
– Freq. difference = +/- 0 to 3 Hz for In-phase
– Phase Angle closed or in-phase, when the number of Gen-
erators = 0, the phase angle difference is fixed at +/- 8
degrees
– Phase Angle closed or in-phase, when the number of Gen-
erators = 1 or 2, the phase angle difference is fixed at +/-
5 degrees
• The controller attempts to close or in-phase transition until the
Sync Timer's set point (1 to 60 min) expires.
Synchroscope Data for In-phase & Closed Transitions
The synchroscope is a useful tool for sync type transitions. When
the controller is waiting for synchronization for either In-phase or
Closed transitions, there is a timer countdown and the display will
show the following:
Phase Angle xxx degrees Sync Timer hh:mm:ss
The phase angle is between 0 and 365 degrees. On each closed
transition type switch, there is a parallel limit timer that either
opens the breaker or sends a close to user terminal blocks (con-
tactor types) that can be used to open breakers upstream, if the
overlap time is greater than what was set by the user. Please
check the switch instruction booklet for more information.
Section 2: Hardware Description
2.1 General
The purpose of this section is to familiarize the reader with ATC-
900 hardware, its nomenclature, and to list the unit’s specifica-
tions. The information presented is divided into the following four
parts:
• Operator Panel;
• Rear Access Area;
• External Hardware; and
• Specification Summary.
2.2 Operator Panel
The operator panel, which is normally accessible from the outside
of a panel or door, provides a means for:
• Being alerted to specific conditions;
• Receiving functional help;
• Programming; and
• Parameter Monitoring/Selection/Metering.
LEDs, a display, pushbuttons, and a mimic bus make up the front
accessible operator panel (Figure 1).
The Color high resolution TFT LCD is used to display all ATC-900
monitored parameters, setpoints and messages in an easy to read
format. The display is approximately 2.25" x 4" (57.15mm x
101.6mm). The TFT display is not a touch screen.
The front operator panel supports seven long-life extended tem-
perature membrane pushbuttons.
2.3 Rear Access Area
The rear access area of the ATC-900 is normally accessible from
the rear of an open switch panel door (Figure 2).
All wiring connections to the ATC-900 are made at the rear of the
chassis. For the sake of uniform identification, the frame of refer-
ence when discussing the rear access area is facing the back of
the ATC-900 with the panel door open. Keeping safety in mind,
programming and downloading setpoints, history, and events can
all be accomplished with the front door closed. A USB connector
with a cover is brought out from the back of the controller to the
front of the door on the switch using the device panel.
2.3 .1 Connections on Chassis
The rear of the chassis provides self locking female connectors.
See Figure 2 for connections for the left, right, and top of the
ATC-900. See Section 4 for more information on input functional-
ity. The part numbers of the connectors are shown below:
Connector Designation
J1 Source 1 Sense Lines
J2 Source 2 Sense Lines
J3 Load Sense Lines
J4 Programmable Outputs (4) & Source Available Form C
J5 RS-232 (Factory Use)
J6 Transfer Control and Aux Inputs
J7 Control Power from Sources 1 and 2 (see note below)
J8 USB Stick (thumb) Drive Connection (connector brought out to
front door panel)
J9 Programmable Inputs (4)
J11 I/O Module Interface
J12 Modbus 485 (User)
J13 RS-422 (Future Use)
J14 DCT Module Interface
Note: Controller power for Source 1, J7-1,2 must be electrically isolated
from control power for Source 2, J7-3,4.
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