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Page 18
SECTION 5: OPERATION
5.1 GENERAL
!
THIS PRODUCT CONTAINS A SPECIAL CONTACT
ARRANGEMENT (OVERLAPPING CONTACTS). MIS-
USE CAN RESULT IN DEATH, SEVERE PERSONAL
INJURY AND/OR PROPERTY DAMAGE.
A transfer switch provides main contacts to connect and
disconnect the load to and from the normal and emer-
gency power sources (Paragraph 3.2.1). A stored-energy
type transfer mechanism provides the mechanical motion
required to open and close the main contacts (Paragraph
3.2.4 and Figure 3-2).
Each switch can be manually operated. Before a switch-
ing device can be closed, the stored energy mechanism
must be charged by pumping the handle (Figure 5-1).
A single switching device can be manually closed by fol-
lowing the instructions detailed in Figure 5-2.
NOTICE
If a transfer switch with any type of electrical operat-
ing capabilities is to be operated manually utilizing
the manual operating handle, it is strongly recom-
mended that the transfer control circuit first be iso-
lated. This is accomplished by disconnecting the
Figure 5-1 Pumping Handle Charges Stored Energy
Mechanism
WARNING
logic panel. In the case of the automatic transfer
switch design, any attempt to operate the manual
handle without first isolating the control circuit
causes an automatic transfer.
5.2 AUTOMATIC TRANSFER SWITCH
The operating sequence of a closed transition automatic
transfer switch is dictated by the switch's standard fea-
tures and selected options. Operation of an automatic
transfer switch during normal power source failure, nor-
mal power source restoration and performing tests will
be described here with only standard options included
on the switch. Additional options, as described in
Section 3 or in separate instruction documents, can
change sequences and timing depending upon the
options selected. Become familiar with any additional
options selected and their effect on the normal operation
of an automatic transfer switch.
Normal Power Source Failure
Standard normal power source failure is defined as a
reduction or loss of voltage. If this occurs, the sequence
of operation is as follows:
·
Failure of the normal power source is detected by
the logic.
·
When the intelligence circuit detects a failure, the
normal relay drops out, opening certain contacts
while closing others. One of the contacts starts the
engine-driven generator.
·
When the emergency power source voltage reaches
its operation rating, an emergency relay closes,
starting the transfer operation. This operating
sequence opens the normal switching device and
closes the emergency switching device.
·
The load is now transferred to emergency power
source.
Normal Power Source Restoration
A return to the normal power source begins when the
voltage in all phases of a 3-phase sensing unit or volt-
age in a single phase sensing unit is restored to a pre-
set value.
·
At the preset pickup voltage, the logic causes the
normal relay to pickup.
I.B. ATS-CP01
Effective 5/98
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