GENERATOR

Portable Generator Familiarization & Troubleshooting Guide
Section 3 • Generator Diagnostics and Adjustments
Troubleshooting Sincro® Wound
Generators (Brushless Type)
Refer to Figure 3.46
Test 1: — Check (AC) Frequency and Voltage
Connect an accurate (AC) frequency meter across the two
parallel blades of one of the panel 120VAC receptacles.
• Start the engine and let it stabilize.
Read the (AC) frequency.A frequency reading of 61-63
Hertz should be obtained.
If frequency is not within specifications:
• Consult the appropriate engine service manual for
adjustment.
With the generator engine running, connect the VOM test
probes across the parallel blades of the panel 120VAC
receptacles.A reading of approximately 130-140VAC should
be indicated.
If voltage checks as specified:
• Discontinue test.
If voltage reading is zero:
• Go to Test 2:“Flash The Field.”
If voltage reading is low:
• Go to Test 3:“Check The Rotor.”
Test 2: — Flash The Field
To restore magnetism in a generator having a capacitor
excitation system, an energizing cord may be made locally
(Figure 3.47).
Figure 3.47 — Energizing Cord
• Run the engine for 10 seconds, then shut the engine
OFF.
• Unplug the energizing cord from the generator
receptacle and from the wall receptacle.
• Restart the generator engine and check (AC) voltage.
Test 3: — Check Rotor Resistance
• Set your VOM to its “OHM” scale.
• Check both coils of the rotor individually (Figure 3.48).
Figure 3.48 — Rotor Winding Resistance
Meter
Test Points
• Compare readings with those found in the Briggs &
Stratton Power Products ® “Portable Generator
Rotor/Stator Resistance Tables Pub. #87971 Rev 6 or
later.
Check the rotor for a “short to ground” as shown in
Figure 3.49.
Figure 3.49 — Rotor Winding Resistance
• Make sure the generator is completely assembled.
• Plug one end of the energizing cord into one of the
panel 120VAC receptacles.
• Start the generator engine.
• Plug the opposite end of the energizing cord into a
120VAC wall receptacle.
Meter
Test Points
85