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IB140012EN
Instructional Booklet
Page
36
Effective: March 2021
Operation and Maintenance Manual,
Automatic Transfer Switch Controller, ATC-900
Feature 23: Plant Exerciser
This feature provides for the automatic test operation of the gen-
erator at a pre-selected weekly interval. When the test is running,
pressing and releasing the Engine Test pushbutton will cancel the
test. The day of the week, hour, and minute that exercising is
desired can be programmed into the ATC-900. Up to twelve sepa-
rate month and day combinations can be set. The type of test,
whether a load transfer or just an engine test, can also be selected
(see information about External setting in Engine Test Mode). Load
testing is fail-safe. If the generator fails during testing for any rea-
son, the ATC-900 will signal the transfer switch to return to the
Preferred source. The ATC-900 is factory shipped with this fea-
ture set to off.
Feature 26D: Go To Emergency
This feature enables an external contact closure to initiate a trans-
fer from the Preferrd Source to the Non-preferred Source. If the
external contact is closed and the Non-preferred Source fails, the
ATC-900 will transfer the load back to the Preferred Source.
Feature 26J: Undervoltage Monitoring for Source 1
This feature constantly monitors Source 1 for an undervoltage
condition. When the Source 1 voltage drops to a value equal to or
below the undervoltage dropout setting, the source will become
unavailable. The source’s voltage will then have to rise to a value
that is equal to or above the pickup setting to become available
again.
Underfrequency Monitoring for Source 1
This feature constantly monitors Source 1 for an underfrequency
condition. When the Source 1 frequency drops to a value equal to
or below the underfrequency dropout setting, the source will
become unavailable. The source’s frequency will then have to rise
to a value that is equal to or above the pickup setting to become
available again. This can be disabled in the setpoint settings under
menu 2 in the Setpoints Dropouts/Pickups.
Feature 26K: Overvoltage Monitoring for Source 1
This feature constantly monitors Source 1 for an overvoltage con-
dition. When the Source 1 voltage rises to a value equal to or
above the overvoltage dropout setting, the source will become
unavailable. The source’s voltage will then have to drop to a value
that is equal to or below the pickup setting to become available
again. This can be disabled in the setpoint settings under menu 1
in the Setpoints Dropouts/Pickups.
Overfrequency Monitoring for Source 1
This feature constantly monitors Source 1 for an overfrequency
condition. When the Source 1 frequency rises to a value equal to
or above the overfrequency dropout setting, the source will
become unavailable. The source’s frequency will then have to
drop to a value that is equal to or below the pickup setting to
become available again. This can be disabled in the setpoint set-
tings under menu 2 in the Setpoints Dropouts/Pickups.
Feature 26L: Voltage Unbalance Monitoring for Source 1
This feature constantly monitors Source 1 for a voltage unbalance
condition using symmetrical components calculations. When the
ratio of negative sequence to positive sequence voltage (V2/V1)
exceeds the unbalance dropout setting the Unbalance/Phase Loss
time delay starts counting. If the timer expires before the unbal-
ance is resolved the source will become unavailable. The unbal-
ance must drop to a value that is below the pickup setting to stop
the timer or to become available after the timer expires. This can
be disabled in the setpoint settings under menu 3 in the Setpoints
Dropouts/Pickups.
Feature 26M: Voltage Phase Loss for Source 1
This feature constantly monitors Source 1 for a phase loss condi-
tion using symmetrical components voltage calculations. When
the ratio of negative sequence to positive sequence voltage (V2/
V1) exceeds the phase loss dropout setting the Unbalance/Phase
Loss time delay starts counting. If the timer expires before the
phase loss is resolved the source will become unavailable. The
phase loss must drop to a value that is below the pickup setting to
stop the timer or to become available after the timer expires. This
can be disabled in the setpoint settings under menu 3 in the Set-
points Dropouts/Pickups.
Feature 29J: Manual Retransfer
This feature provides for a selection between an automatic trans-
fer and re-transfer mode or a manual pushbutton re-transfer to
Normal from the Emergency Source mode. The External option
requires a programmable input set to Enable Man Retran and con-
nected to a two position switch. When the switch is open auto-
matic re-transfer occurs, when closed the manual pushbutton re-
transfer is selected. When either the Manual or External option is
selected a programmable input set to Man Retransfer and con-
nected to a normally open pushbutton switch is required to initiate
the retransfer. If this option is not selected the factory default
selection is automatic.
Feature 32A: Time Delay Neutral
This feature provides a time delay in the transfer switch Neutral
position when both breakers/contactors are open. This delay takes
place when the load is transferred in either direction to prevent
excessive in-rush currents due to out-of-phase switching of large
motor loads. This feature is not available with the Neutral Load
Sense Delay (TDNLD) feature.
Feature 32B: Load Voltage Decay
This feature utilizes the load voltage measurements to sense back
EMF that is generated when the transfer switch is in the Neutral
position. It provides a delay in transfer in either direction if an
unacceptable level is sensed as established by a customer pro-
grammed level. The transfer will not take place until the back EMF
decays below the acceptable programmed level. This feature has a
separate setting of enabling or disabling the operation. If disabled,
the transfer switch will not delay in the Neutral position and will
transfer between the sources as fast as possible. This feature is
not available with the Time Delay Neutral (TDN) Feature 32A.
Feature 32C: In-Phase/Load Voltage Decay
In-phase transition is a feature that will allow a transfer between
two live sources only when the phase difference between the two
sources is near zero. This is an open transition transfer that pre-
vents in-rush currents from exceeding normal starting currents in
the case where motor loads are being transferred.
Load Voltage Decay utilizes the load voltage measurements to
sense back EMF that is generated when the transfer switch is in
the Neutral position. It provides a delay in transfer in either direc-
tion if an unacceptable level is sensed as established by a cus-
tomer programmed level. The transfer will not take place until the
back EMF decays below the acceptable programmed level. This
feature has a separate setting of enabling or disabling the opera-
tion. If disabled, the transfer switch will not delay in the Neutral
position and will transfer between the sources as fast as possible.
This feature is not available with the Time Delay Neutral (TDN)
Feature 32A.
