TROUBLESHOOTING
TESTING AND ADJUSTING
POSSIBLE CAUSES
VERIFICATION PROCEDURE
7. Open or Short Circuit
Disconnect the rotating field (L5) by removing the wire- to
positive heat sink (E1) and negative heat sink (E2). Check the
continuity of rotating field (L5). NOTE: To measure the
resistance of the rotating field, use a Kelvin or Wheatstone Bridge.
Typical resistance is less than one ohm. Keep the wires from
rotating field (L5) to heat sinks (E1) and (E2) disconnected.
Check the continuity of exciter armature (L4) at the terminal
connections of rotating rectifiers (CR1 thru CR6). NOTE: To
measure the resistance of the exciter armature coils use a Kelvin
Bridge. Typical resistance is much less than one ohm, from
terminals of rotating rectifiers (CR1) to (CR2) etc.
Disconnect load from generator, either by opening the line circuit
breaker or disconnecting the load cables from (T1) (T2) (T3) and
(T0). Disconnect the regulator assembly from stator (L6)
removing the wires at terminals (20. 22. 24 and 26). Check the
generator line lead connections against those shown on the
generator name plate. Check continuity of stator (L6) windings.
NOTE: To measure the resistance of the stator (L6) windings use a
Kelvin Bridge. Typical resistance, between phases. is much less
than one ohm.
8. Grounded Circuit
Moisture (water), dust, grease and other foreign matter can cause a
change in the resistance characteristics of the insulation on the
conductors of the stator and rotor. This is "surface leakage."
Measure the resistance of the insulation when the generator Is
warmer than the air around it. Disconnect the rotating field (L5)
by removing the wires to heat sinks (E1) and (E2). Check the
resistance of the insulation of rotating field (L5) to ground.
NOTE: Resistance of the insulation must be clone with a
megohmeter. Resistance must not be less than on megohm
(1,000,000 ohms).
Connect the rotating field (L5) to the respective heat sink (E1)
and negative end to heat sink (E2), Measure the resistance between
heat sink (E1) and ground. Use a standard ohmmeter. Turn scale
to RX1000. Resistance to ground will be through suppression
resistor (R6) and must be 27,000 ohms plus or minus 10 percent.
Remove the bolts that connect the exciter armature (L4) cables to
the terminals of rotating rectifiers (CR1 thru CR6). Temporarily
use tape for insulation of all wires, except one. This will prevent
an accident if one of the wires is grounded. Use a megohmeter to
measure the resistance of the insulation on the exciter armature
(L4) windings between the wire with no tape and ground. The
resistance must be one megohm or more.
NOTICE: The voltages from the megohmeter can cause
permanent damage to the rotating rectifiers (CR1 thru CR6).
They must not be connected to the exciter armature (L4)
during the test.
Remove wires (F1) and (F2) from terminal connections (F1) and
(F2). Use a megohmeter and measure the resistance of the
insulation of exciter field (L3). Connect the meter between either
wire, (F1) or (F2) and ground. Resistance must be one megohm or
more.
(Continued on next page)
63
