TS 910 TRANSFER SWITCH
PM140 REV 2 14/01/23 38 Thomson Power Systems
18.8 TSC 9 OPERATING MODE DESCRIPTIONS
18.8.1 TRANSFER SWITCH FAIL ALARM LOGIC
The TSC 9 controller contains logic to detect abnormal operation during various
failure modes. Detailed operating logic is as follows:
18.8.1.1 Utility Limit Switch Failure:
Should the utility power contactor limit switch fail to close when the contactor
is in the utility position, an alarm condition will be activated after a 10 second
delay. This alarm condition will cause the following events to occur:
• Force Transfer: a forced transfer to the generator supply will be
activated. A generator start signal will be initiated to start the
generator and load will transfer to the generator supply if within
normal limits. Re-transfer back to the utility supply will not occur
until the Transfer Fail alarm condition is reset.
• ‘On Utility’ LED Flashes: the “On Utility’ LED will begin flashing
to indicate that the utility limit switch is not operating correctly.
The LED will flash until the alarm condition is reset.
• ‘Alarm’ LED Activated: the ‘alarm’ LED’ will be activated. The
LED will not go out until the alarm condition is reset.
• Alarm Output Signal Activated: the output signal on customer
terminals #5 & #6 will be activated. The alarm output signal will
be terminated once the alarm condition is reset.
18.8.1.2 Generator Limit Switch Failure:
Should the generator power contactor limit switch fail to close when the
contactor is in the generator position, an alarm condition will be activated after
a 10 second delay. This alarm condition will cause the following events to
occur:
• Force Transfer: a forced transfer to the utility supply will be
activated. The load will automatically be transferred to the utility
supply if within normal limits. Re-transfer back to the generator
supply will not occur until the Transfer Fail alarm condition is
reset and the generator is still called to start for Test or Exercise
operating modes.
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