IB140058EN
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Instructional Booklet
Effective: March 2016
Page
17
O&M Manual for 30-1000 Amperes
Manual Transfer Switch
Section 5: Operation
5.1 General
A transfer switch provides main contacts to connect and discon-
nect the load to and from the normal and emergency power
sources (Section 3.2.2). A transfer mechanism provides the
mechanical motion required to open and close the mechanically
interlocked main contacts (Sections 3.2.3, 3.2.4 and Figure 8).
Three distinct switch positions are provided:
•
Normal:
The contacts associated with Source 1 are closed and
the Source 2 contacts are open.
•
Neutral:
The contacts associated with both the Source 1 and
Source 2 are open. This position allows for load circuit mainte-
nance.
•
Emergency:
The contacts associated with Source 1 are open
and Source 2 contacts are closed.
5.2 Vertical Design Operation
The vertical design transfer switch utilizes a mechanical mecha-
nism with a manual operating handle (Figure 15). The manual
operating handle can be used to create the rotational motion
required to open and close the main contacts through a rigid
mechanical interlocking system (Figure 18). An indicator wheel
attached to the operating handle and mechanical interlocking sys-
tem rotates with each movement of the handle to open and/or
close the main contacts (Figure 19). The three switch positions
(Normal, Neutral and Emergency) are visually indicated on the indi-
cator wheel (Figure 20).
To manually operate the transfer switch, the operating handle is
ratcheted until the desired switch position is indicated on the indi-
cator wheel. The operating handle is always electrically "dead,"
and the indicator wheel free-wheels should a particular switch be
capable of electrical operation through the use of a motor. This
feature ensures no operator problems should the switch automati-
cally operate while the manual handle is being used.
Figure 17. Transfer Switch Manual Operating Handle in Use on
Vertical Design.
Figure 18. Indicator Wheel Shown Mounted in Mechanism with
Motor Mounted Under Wheel.
5.3 Horizontal Design Operation
The horizontal design transfer switch utilizes a pivoting rocker-arm
lever which operates the circuit breaker handles as the arm is
moved by a rotating lever usually connected to a transfer motor
(Figure 16). A slide pin engaging a pivot in the rotating lever con-
verts rotary motion to linear motion.
To operate breaker manually or if the breaker trips, 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 to re-engage the motor.
Figure 19. Indicator Wheel Indicating Neutral Position on Vertical
Design.
