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 […]
How to Test a Generator AVR?
To test a generator AVR, I first check the generator frequency, AVR wiring, AVR power supply, voltage sensing, and excitation output. If the AVR has the correct supply and sensing input but does not provide the expected excitation response, I then suspect the AVR itself. In our experience, replacing the AVR before these checks is […]
What Causes a Generator AVR to Fail?
A generator AVR usually fails because of abnormal voltage or excitation, incorrect wiring, excessive heat, vibration, moisture, or a fault elsewhere in the alternator excitation system. In our experience, if an AVR fails once, replacing it may solve the problem. But if the new AVR fails again, I would stop replacing AVRs and look for […]
Why Does Generator Voltage Drop Under Load?
If your generator voltage is normal at no load but drops when load is applied, first check the actual load and watch the frequency at the same time. In our generator testing, this is usually the fastest way to narrow down the problem. If voltage and frequency both drop, I normally check the load and […]
Why Does Generator Voltage Fluctuate?
Generator voltage can fluctuate because of unstable engine speed, AVR problems, poor sensing connections, excitation faults, loose wiring, or sudden load changes. In our experience, the first thing to check is frequency. If voltage and frequency move up and down together, I normally check engine speed, governor response, and load changes first. If frequency stays […]
Why Is My Generator Voltage Too High?
If your generator voltage is too high, first check the output frequency, engine speed, AVR voltage setting, and AVR sensing circuit. High voltage can also be caused by loose sensing wires, incorrect alternator connections, a wrong AVR model, a faulty AVR, or an excitation system problem. In our experience, we do not replace the AVR […]