6-4
GENERATOR TESTING
Rotor Tests
Test the rotor for grounded, open and shorted wind-
ings using an ohmmeter. First test at the brush block
terminals. If the resistance is high, remove the brush
block and test directly on the slip rings. Replace the
brush block if a high resistance is due to the
brushes.
Ground Test: Set the ohmmeter to the highest re-
sistance scale, or use a megger. Touch one test
prod to the rotor shaft and the other to one of the slip
rings. Replace the rotor if the reading is less than
one megohm (one million ohms) on a megger, or in-
finity on an ohmmeter.
Winding Resistance Test: Touch the slip rings
with the meter test prods. Replace the rotor if resist-
ance is not as specified in Table 6-1 or 6-2, as ap-
propriate.
TABLE 6-1. ROTOR—HGJAA, HGJAB, HGJAC
RESISTANCE (OHMS) @ 77° F (25° C) ± 10%
6.5-7.0 kW Gensets
(95 mm Stack)
5.5 kW Gensets
(80 mm Stack)
31.97 29.34
TABLE 6-2. ROTOR—HGJAD, HGJAE, HGJAF
RESISTANCE (OHMS) @ 77° F (25° C) ± 10%
31.97
Stator Tests
Use an ohmmeter to test for grounded or open wind-
ings. Remove the control enclosure for access to
the stator leads (Section 5. Control).
Ground Test: Set the ohmmeter to the highest re-
sistance scale and then touch one test prod to the
stack and, in turn, the other to each stator lead. Re-
place the stator if any reading is less than one meg-
ohm (one million ohms) on a megger, or infinity on
an ohmmeter.
Open Winding Test: Connect the ohmmeter test
prods across each pair of winding leads. Replace
the stator if any winding is open (zero ohms).
Winding Resistance Test: Use a meter (Wheat-
stone Bridge) having a precision down to
0.001 ohms to measure resistance across each pair
of winding leads. Replace the stator if resistance is
not as specified in Table 6-3 or 6-4, as appropriate.
TABLE 6-3. STATOR—HGJAA, HGJAB, HGJAC
RESISTANCE (OHMS)
@ 77° F (25° C) ± 10%
WINDING
6.5-7.0 kW Gensets
(95 mm Stack)
5.5 kW Gensets
(80 mm Stack)
T1–T2,
T3–T4
0.30 0.33
Q1–Q2 2.44 2.73
TABLE 6-4. STATOR—HGJAD, HGJAE, HGJAF
WINDING
RESISTANCE (OHMS)
@ 77° F (25° C) ± 10%
120 V, 1-PH
T1–T2 0.147
Q1–Q2 2.42
B1–B2 0.124
120/240 V, 1-PH
T1–T4* 0.294
Q1–Q2 2.42
B1–B2 0.124
3-PH (DELTA)
L1–L2, L1–L3,
L2-L3
1.05
Q1–Q2 3.28
B1–B2 0.276
* – T2 and T3 must be connected for this test.
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