How to Solve Unstable Voltage of Generator Set

1. Check the automatic voltage regulator (AVR)

The AVR is the core component for voltage adjustment. Loose wiring, burnt‑out components or improper parameter setting will cause voltage fluctuation. Check whether the terminals are firm; calibrate AVR parameters according to the manual; replace a new AVR if it is damaged.

2. Inspect carbon brushes and slip rings

For brush‑type generators, worn carbon brushes, weak spring pressure, or dirty, oxidized slip rings will lead to unstable excitation. Check carbon brush wear, replace severely worn brushes, and polish and clean slip ring surfaces.

3. Check engine speed (frequency)

Generator voltage is closely related to rotational speed. Unstable diesel engine speed will directly cause voltage swing. Troubleshoot fuel supply system: fuel filter blockage, fuel pump failure, governor malfunction. Clean or replace filter elements, repair the governor to keep steady rotational speed.

4. Check load conditions

Frequent large‑magnitude load switching, unbalanced three‑phase load, or excessive impact load will result in voltage fluctuation. Avoid frequent sudden loading/unloading; balance three‑phase current; add buffer measures for impact loads. Do not operate under serious overload.

5. Examine wiring and connection terminals

Loose, oxidized or corroded main circuit terminals, cable joints will produce contact resistance and cause voltage instability. Tighten all connecting bolts, remove oxide layers, and replace aging cables.

6. Check excitation circuit

Poor contact of excitation winding, short‑circuit or open‑circuit faults will affect excitation output. Measure winding resistance and insulation resistance, eliminate short‑circuit and grounding faults.

7. Environmental and cooling conditions

Excessive operating temperature of the generator will change winding characteristics and cause voltage drift. Keep good ventilation and heat dissipation; clean dust on stator and rotor windings.

8. Fault of voltage measuring instruments

Confirm whether the voltmeter or multi‑meter itself is abnormal. Use calibrated measuring equipment to verify real output voltage, avoid misjudgment caused by instrument failure.

9. Generator winding faults

Local turn‑to‑turn short‑circuit of stator or rotor winding will cause persistent abnormal voltage. Carry out insulation test and winding inspection; perform winding repair if internal damage occurs.