IB140058EN
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Instructional Booklet
Effective: March 2016
Page
7
O&M Manual for 30-1000 Amperes
Manual Transfer Switch
The components comprising the three panels are installed in
accordance with the specific requirements of the circuit being
controlled. Each transfer switch is, therefore, tailor-made to a
specific application.
3.2 Power Panel
The power panel consists of a means for making load, power and
neutral connections, the main contacts and the transfer mecha-
nism all on one steel base plate (Figures 6 and 7).
Figure 7. Typical Horizontal Design Power Panel (Mounted).
3.2.1 Vertical Design Steel Base Plate
The steel base plate on the vertical design permits the power
panel to be moved vertically within the enclosure to accommodate
top or bottom cable entry (Figure 13). Elongated holes on either
side of the base plate ensure proper positioning. The bottom set of
elongated holes position the power panel higher in the enclosure,
thus permitting bottom cable entry. The top set of elongated holes
position the power panel lower in the enclosure for top cable
entry. Section 4 discusses equipment mounting and load lug loca-
tion in detail.
3.2.2 Main Contacts
The main contacts connect and disconnect the load to and from
the different power sources. High withstand molded case
switches are the main contacts for the Norm and Emergency
power sources in standard, unmodified automatic transfer
switches. Optional integral thermal and short circuit protection in
either or both switching devices however, available (Figure 8 and
Section 3.5). These contiuous duty switches are rated for all
classes of loads, open or enclosed. In addition, they have high
dielectric strength, heavy-duty switching and withstand capabili-
ties, and high interrupting capacity. The switches incorporate pos-
itive, quick-make, quick-break toggle mechanisms and DE-IONT
arc chutes.
Vertically mounted switching devices are mechanically and electri-
cally interlocked to prevent the two sets of main contacts from
being closed simultaneously. The load side contacts of each
switching device are joined with a bus bar assembly to form a
common load terminal location, either top or bottom (Figure 14).
Horizontally mounted switching devices are also mechanically and
electrically interlocked. The molded case switch are kept trip-free
in the closed position. This permits ther and short circuit protec-
tion to be incorporated in either or both interrupters.
3.2.3 Vertical Design Transfer Mechanism
The transfer mechanism transfers between power sources through
a motor driven ratchet type operation. A rotational motion is cre-
ated on an indicator wheel by the ratchet's operation. The indica-
tor wheel is attached to rigid shafts which covert the rotary
motion into vertical linear motion. Opening and closing of the
switching devices is accomplished as a result of this vertical linear
motion. The transf mechanism is mounted in front of the molded
case switch (Figure 6).
A solid steel shield attached to the ratchet assembly perm viewing
of the rotary switch position indicator while restriing access to
other parts of the power panel (Figure 3).
3.2.4 Horizontal Design Transfer Mechanism
The horizontal design mechanism consists of a pivoting rocker-arm
lever which operates the switch handles as the arm is moved by a
rotating lever connected to the transfer motor. A slide pin engag-
ing a pivot in the rotating lever converts rotary motion to linear
motion. Limit switches are mounted externally to the molded case
switches and operated by the rotating lever. Each limit switch is
synchronized with its associated molded case switch to operate
when its switchcloses (Figure 7).
Figure 8. Molded Case Switches Mounted in Vertical Design
(Transfer Mechanism Removed for Clarity)
