Wiring And Connections; Electrical System (115-V Ac); Monitoring Instruments; Indicating Lights - Hobart 6921 Series Operation And Maintenance Manual

OM-2040 / Operation and Maintenance Manual
90D20 / Generator Sets
c. Wiring and Connections
(1) Inspect all cables and leads for broken, worn, and damaged insulation.
(2) Check for loose connections and tighten.
NOTE: A darkened terminal generally indicates a loose connection.

4. Electrical System (115-V AC)

The 400-Hz generator and controls are designed to be as maintenance free as possible. No lubrication
or periodic maintenance adjustments are required. However, some regular checks should be made to
be sure all controls, instruments, etc., are working properly.
a. Monitoring Instruments
Observe operation of voltmeter, ammeter, and frequency meter each time the unit is started.
b. Indicating Lights
Check lamps (bulbs) in all of the indicating lights of each start up. Fault indicating lights in the
protective relay tray may be tested by pressing test switch (1-1, 8, Fig. 9) .
c. Protective Modules
Check operation of all protective modules to ensure they will function if a fault should occur in the
output circuit. (see 2-3; Para. 3, B) .
d. Wiring Connections
(1) Check all cables, leads, and wiring for broken, worn and damaged insulation.
(2) Inspect connections for tightness.
WARNING
High voltage: electric shock can kill! Stop operations and stop engine before
touching exposed conductors or terminals.
(3) Check the output cable plug connector for damaged contactors in the end of the plug.

5. Inspection of Transformer-Rectifiers

A periodic inspection schedule should be established and maintained for T-R's. Inspections should be
scheduled to coincide with similar inspections for the generator set. Inspect as follows:
a. Open front control panel and rear access panel. Remove top cover.
WARNING
Be sure not input power can reach the t-r. Lethal electrical shock hazard exists.
b. Inspect leads and cables for deteriorated or damaged insulation.
c. Check all accessible terminals and connectors for security.
d. Visually inspect all components, terminals, etc., for discoloration and evidence of overheating
caused by loose connections, etc.
e. Check both fuses located on control panel.
f. Use dry, compressed air to clean the interior of the T-R each time it is inspected.
Chapter 2-2
Page 4
February 28/94 Revised