What Causes a Generator Exciter to Fail?
A generator exciter can fail because of winding overheating, insulation breakdown, moisture or contamination, loose connections, excessive excitation current, or faults elsewhere in the excitation system. But in our experience, low or no generator voltage does not automatically mean the exciter has failed. We normally check the AVR, wiring, excitation supply, and rotating diodes first. […]
What Causes Generator Alternator Windings to Burn Out?
Generator alternator windings usually burn out because of excessive current, overheating, phase imbalance, poor cooling, insulation breakdown, moisture or contamination, loose connections, or an internal electrical fault. In our experience, a burned winding is often the result of another problem, not the original fault. If we only rewind or replace the alternator without finding that […]
What Are the Signs of Generator Alternator Winding Failure?
The most common signs of generator alternator winding failure are repeated overheating, a burnt insulation smell, dark or damaged windings, unbalanced voltage, poor voltage under load, low insulation resistance, and abnormal winding resistance. But I would not diagnose a failed winding from low voltage or overheating alone. In our generator testing, we normally rule out […]
Why Is My Generator Alternator Overheating?
If a generator alternator is overheating, I normally check the load current, phase balance, cooling airflow, power factor, frequency, and electrical connections first. I would not open the alternator or replace the AVR just because the alternator feels very hot. In our generator testing, an alternator getting hot under load is normal. What matters is […]
Why Does a Generator Produce Unbalanced Voltage?
When a generator produces unbalanced voltage, I first check whether the voltage is already unbalanced at no load or only becomes unbalanced after load is applied. If the three-phase voltage is balanced at no load but becomes unbalanced under load, I normally check phase loading, cables, terminals, breaker and ATS connections first. If the voltage […]
How to Check Generator Alternator Windings?
To check generator alternator windings, I normally do three things: compare the phase winding resistance, test insulation resistance to ground, and inspect the windings and connections for overheating or damage. If one phase is open or clearly different from the others, or the insulation resistance to ground is poor, I start to suspect a winding […]
How to Test Generator Rotating Diodes?
To test generator rotating diodes, stop the generator, isolate the starting battery, and access the rotating rectifier assembly. We normally use a multimeter in diode mode and test each diode in both directions. A good diode should conduct in one direction and block in the other. If it conducts in both directions, or shows open […]
What Causes Generator Rotating Diodes to Fail?
Generator rotating diodes usually fail because of excessive current, overheating, loose connections, electrical faults, or problems in the exciter or rotor circuit. If we find a failed diode, we do not simply replace it. We first test all the rotating diodes, inspect the rectifier connections, and check the exciter and rotor circuit for signs of […]
Why Does a Generator Lose Excitation?
A generator usually loses excitation because the AVR is not providing the correct field current, the excitation circuit is open, residual magnetism has become too weak, or there is a fault in the rotating diodes, exciter, or alternator windings. When we see this problem during generator troubleshooting, I do not replace the AVR first. I […]