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TP-6461 1/08 16 Section 1 Scheduled Maintenance
Transfer Switch Inspection. Remove the arc chute
assemblies or covers at the front of the transfer switch
and inspect the main contacts inside the transfer switch.
See Figure 1-1 or Figure 1-2.
Note: A clamp or fixture must be attached before
removing the arc chutes on 600-amp Model KSP
programmed-transition
switches. See
Section 7.3.7 for complete instructions.
Remove surface deposits with a clean cloth. Do not use
an emery cloth or a file. Discoloration of the contact
surface does not affect performance. If the contacts are
pitted, show signs of overheating, or are worn, replace
the contacts.
The contacts are worn if the contact
surface material, a layer of silvery-colored metal, is worn
through to the metal below. Check the condition of the
arc chutes. If arc chutes show signs of disintegration,
replace the arc chute assembly.
6226
1. Arc chute assemblies
1
Figure 1-1 Typical Arc Chute Assemblies, Model
KSS
6226
1. Arc chute retainer clips
1
Figure 1-2 Typical Arc Chute Assemblies, Model
KSP
1.3 Testing
Periodic testing is important in any transfer switch
application. It helps to ensure that the generator set will
start and the transfer switch mechanisms and control
circuits will operate when needed.
1.3.1 Weekly Generator Set Exercise
Use the plant exerciser to start and run the generator set
once a week to maximize the reliability of the emergency
power system. See the transfer switch operation and
installation manual for additional information about the
exerciser.
1.3.2 Monthly Automatic Operation Test
Test the transfer switch’s automatic control system
monthly.
See Section 4.5.4 or the transfer switch
operation and installation manual for the test procedure.
Verify that the expected sequence of operations occurs
as the switch transfers the load to the emergency source
when a normal source failure occurs or is simulated.
After the switch transfers the load to the emergency
source, end the test and verify that the expected
sequence of operations occurs as the transfer switch
retransfers to the available normal source and signals
the generator set to shut down after a cooldown period.
Note: The ATS will not transfer the load during the test
sequence if the test DIP switch is set to the
unloaded position.
1.3.3 Other Tests
Every Year
Measure the voltage drop to help locate high-resistance
contacts in the ATS. The test procedure measures the
voltage drop across a contact and the current in the
circuit, then uses those measured values to find the
contact resistance.
The purpose of the test is to locate any contact that has
significantly higher resistance than others.
An
unusually high voltage across one set of contacts may
signal unacceptably high resistance in the contacts.
Run the test with the ATS under a moderate and
balanced load. Use the following procedure to take
voltage measurements and calculate resistances for
each phase of both Source N and Source E.