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TM 5-685/NAVFAC MO-912
tion resistance between field coils and ground in-
relays such as thermal, current overload, overspeed,
cluding the collector rings. Refer to manufacturer's
liquid level, lubricating oil pressure and/or flow, fre-
instructions. Check bearings and journals for dam-
quency change, etc. Refer to manufacturer's litera-
age or excessive wear. Compare micrometer read-
ture for inspection procedures. Verify that all con-
ings with the manufacturer's table of wear limits.
nections are tight and free of corrosion.
Repair or replace mechanical parts to meet these
(c) Conductors and coils. Clean and inspect
specifications. Dry out according to manufacturer's
conductors and coils monthly. Verify that coating of
instructions. Repair insulation damage and coat
insulating varnish is in good condition (clean,
smooth and polished) and there are no indications of
with approved insulating varnish.
(f) Rotor balancing. Measure and record vi-
overheating or corona arcing.
bration limits of repaired unit when it is started.
(d) Switches. Inspect switches for proper
Refer to manufacturer's specifications for vibration
alignment, firm contacts and smooth operation
limits for the specific unit. Perform static or dy-
monthly. Burned or pitted copper contact surfaces
namic balancing of the unit, according to instruc-
may be dressed with 2/O sandpaper. Do not dress
tions, if necessary.
silver contacts.
(g) Stator winding. Measure and record insu-
(e) Circuit breakers. Trip and close circuit
lation resistance between stator winding and
breakers, check for proper operation quarterly.
ground at the machine terminals annually.
Check time delay and freedom of movement. Refer
(h) Stator service. Open up the stator annu-
to manufacturer's instructions.
ally. Clean thoroughly and inspect for the following:
(f) Coils and heaters. Check coils and heaters
broken, damaged, loose or missing wedges; move-
quarterly for secure mounting and circuit continu-
ment or distortion of coil ends; security of all lash-
ity. Check controls and thermostats for proper op-
ing and spacers; tightness of coil supports; cooling
eration, refer to manufacturer's instructions.
passages are open and clean; looseness of coils in
(g) Contactors. Check magnet surfaces of
slots; cracks or other damage to coil insulation; and,
contactors quarterly for cleanliness. Remove gun,
connections between coils and around the frame.
rust or corrosion. Adjust for even contact pressure
Measure and record insulation resistance between
according to manufacturer's instructions.
winding and ground at the machine terminals.
(h) Voltage regulators. Check voltage regula-
Compare the values with those recorded when the
tors for proper operation and adjustments quarterly.
machine was first put in service.
Various makes and types are used. Refer to the
(3) Checkli st and schedule for solid-state excit-
manufacturer's literature for instructions.
ers. Solid-state equipment does not require long-
b. Long- term. Long-term checklists for switch-
term checks. If the equipment does not function
gear. Performance of tasks is related to frequency
properly, refer to the manufacturer's literature for
and extent of use of the auxiliary power plant.
information. Repair or replace as required.
(1) General comments. The following tasks
7-4. Switchgear maintenance.
should be performed annually unless otherwise
Routine maintenance instructions for switchgear
noted, following performance of short-term checks.
c o n s i s t of short- and long-term checklists.
The procedures are general but apply primarily to
Deenergize switchgear before performing mainte-
draw-out equipment.
nance. Disconnect primary and secondary sources of
(2) Checklist and schedule.
(a) Meters and instruments. Check meters
and instruments against a verified standard. Re-
a. Short-term. Short-term checklists for switch-
turn defective or inaccurate meters and instru-
ments to the manufacturer or designated repair lo-
(1) General comments. Before performing any
cation for service and calibration.
tasks required by the following checklist, review the
(b) Buses. Inspect `buses and connections for
station log sheets, related records, manufacturer's
signs of overheating or weakening of insulating sup-
recommendations and NFPA-70E, Electrical Safety
ports. Overheating is indicated by discoloration of
Requirements for Employee Workplaces.
the busbar. Inspect insulators for cracks and/or arc
(2) Checklist.
tracks. Replace defective insulators. Tighten busbar
(a) Panels and other exterior surfaces. Panels
and terminal connections to the proper torque
and exterior surfaces must be kept scrupulously
clean at all times.
(c) Indicating devices and interlocks. Check
(b) Relays and actuating mechanisms. Clean
indicating devices and interlocks for proper opera-
and inspect relays and actuating mechanisms
tion. Refer to manufacturer's instructions.
monthly. Many types of relays are used. Identify the

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