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Section 5: Operation
5.1 General
A transfer switch provides main contacts to connect and
disconnect 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 maintenance.
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
mechanism with a manual operating handle (Figure 15).
The manual operating handle can be used to create the rota-
tional 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 system 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 indicator
wheel (Figure 20).
To manually operate the transfer switch, the operating
handle is ratcheted until the desired switch position is indi-
cated on the indicator 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 automatically operate while
the manual handle is being used.
IB01602007E
O&M Manual for
Non-Automatic Transfer
Switches (30 – 1200 Amperes)
Figure 18. Transfer Switch Manual Operating Handle in Use on
Vertical Design
Figure 19. Indicator Wheel Shown Mounted in Mechanism with
Motor Mounted Under Wheel
For more information visit: www.cutler-hammer.eaton.com
Instruction Bulletin
Effective: June 2003
Page 21
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