Insulation resistance shall be at least 1 megohm
at 77xF (25xC). If this value is not met, clean or
dry out the winding and repeat test. Replace rotor
Low insulation resistance may be caused by
dirt or excessive moisture. Insulation failure
may be caused by wrong voltages, induced
voltages caused by opening field circuits too
quickly, oil and grease, high temperatures, or
Perform a growler test on the rotor as follows:
Place the rotor on the growler and energize.
Hold a thin piece of metal, such as a
hacksaw blade, directly over the top slot of
the rotor and along the length of the slot. If
the coil is shorted the blade will vibrate
rapidly and cause a growling noise.
If the above test is not met, proceed with
the removal and repair procedures.
Replacement. For removal and replacement of the
generator rotor assembly, the generator must be
removed from the generator set. (See paragraph
11-5b). After generator has been removed from the
generator set, locate it in a suitable maintenance area
affording sufficient accessibility for maintenance and
sufficient unobstructed flow of coolant air. Move the
generator to the maintenance location either by
attaching an overhead hoist to the eyebolts installed
in the generator frame or by lifting the generator from
underneath the base with a fork lift.
Determine that the hoist, when used, is of sufficient
to adequately support the weight of the generator.
Hoist and hoist cables and slings should have a rating
of not less than 6,000 pounds (2,727 kg). when
moving unit with a fork lift, make certain it is
completely onto and balanced on the fork lift tines.
OVERHEAD OPERATIONS HAVE INHERENT
HAZARDS THAT CANNOT BE MECHANICALLY
SAFEGUARDED. HARD HATS AND SAFETY SHOES
Always make certain care is taken when
moving the generator to prevent its striking
other objects or personnel. Never apply a
lifting force to structural points other than
those provided for that purpose.
Avoid maintenance locations which would
moisture, dust, steam or the fumes from
Removal. Remove the rotor from the generator
as follows: (See figure 11-3.)
Remove cover (30) by removing screws (26
and 28), washers (29), and nuts (27).
USE EXTREME CARE WHEN REMOVING ROTOR
TO PREVENT INJURY TO HANDS DUE TO
MAGNETIC ATTRACTION BETWEEN THE PMG
ROTOR AND THE PMG STATOR OR
Remove PMG rotor (37) by removing pin
(36), screw (35), and washer (34).
Do not subject PMG rotor to severe mechanical
Loosen setscrew (52) in exciter rotor (38).