TSC 80e TRANSFER SWITCH CONTROLLER
PM091 Rev 0 09/01/21 Thomson Technology
16
3.1.2.4.TRANSFER FAIL DETECTION-NORMAL STEADY STATE
CONDITION (NON-TRANSFERRING)
i. Limit Switch Failure (i.e. open contact) - Transfer Fail Alarm is initiated
(Load on Source Flashing LED) after a 9-second delay, and then a forced
transfer to the alternate source is initiated, if valid and available. Re-
transfer back to the original source will not occur until the Transfer Fail
alarm condition is reset. Refer to item 3.3 for Transfer Fail Fault Reset
details.
ii. Loss of Load Voltage (<80VAC) (i.e. Power switching device Tripped or
Failed to Close/Conduct Condition) - Transfer Fail Alarm is initiated (Load
Source Flashing LED) after a 5-second delay, then a forced transfer to the
alternate source is initiated, if valid and available. Re-transfer back to the
original source will not occur until the Transfer Fail alarm condition is reset.
Refer to item 3.3 for Transfer Fail Fault Reset details.
iii. Limit Switch Failure & Loss of Load Voltage <80VAC - Transfer Fail Alarm
is initiated (Load Source Flashing LED) after an 11-second delay, then a
forced transfer to the alternate source is initiated, if valid and available. Re-
transfer back to the original source will not occur until the Transfer Fail
alarm condition is reset. Refer to item 3.3 for Transfer Fail Fault Reset
details.
3.1.2.5.TRANSFER FAIL DETECTION - TRANSFERRING CONDITION
Transfer Source to Neutral – “NEUTRAL POSITION TIME” (10 seconds-
adjustable) starts timing as soon as a transfer to the alternate source is
initiated. During this period the ATS motor is energized and moves the
mechanism from the original source to neutral. The power to the motor will be
de-energized when either the “NEUTRAL POSITION TIME” times out or the
load voltage drops below 80VAC on all phases (whichever occurs first). Once
the ATS motor is de-energized, the Neutral Delay timer starts timing (all other
timers are halted while neutral delay timer is running). Once the Neutral Delay
timer expires the motor is re-energized to continue the transfer (see below).
Note: Normally the load voltage will typically drop below the 80VAC setpoint
within 1 second when the source power-switching device opens and therefore
the “NEUTRAL POSITION TIME” never times out. The default setting of this
timer (10 seconds) is intentionally set long so that it will not pre-maturely stop
the ATS mechanism.
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