Eric Salop
Elite Member
Good morning. I'm up early and ready for a good breakfast, in preparation for a hard day of physical activity ahead.
More firewood collecting, chainsawing, post digging ? Nope, something far more tiring - the grandkids are coming :laughing:
David, not much experience with faulty generators so sorry I can't be sure what that is. This would be my first guess from looking at the picture on the scope.
[1] Red arrow. The little discontinuity at each positive and negative zero crossover is typical of a circuit with rectification (guessing diodes in the excitation winding) . Although the voltage waveform is at zero at crossover point, current will still be flowing through a diode and it doesn't "want" to stop immediately. Eventually though the current does stop quite abruptly, so the magnetic field producing the voltage waveform dips, hence the little blips. This suggest both that the diodes are working and that if it uses only a single excitation winding, it has not gone open circuit.
[2] Purple arrow. Voltage has stopped increasing sinusoidally, magnetic field must not be increasing as normal. The field is made up of two parts and much of it is produced by the excitation winding, so very likely not enough current flowing in this winding. But you have already tried another AVR and it doesn't look like the winding is open circuit. Is there a capacitor associated with the excitation winding that is not in the avr circuit you swapped out ? They often have one in series with one, or sometimes two, excitation windings. Alternatively, shorted turns in the winding would lead to early saturation of the magnetic field and give that flat top to the sinusoid - but if that was the problem, I can't think why it would build up in that non linear manner.
More firewood collecting, chainsawing, post digging ? Nope, something far more tiring - the grandkids are coming :laughing:
David, not much experience with faulty generators so sorry I can't be sure what that is. This would be my first guess from looking at the picture on the scope.
[1] Red arrow. The little discontinuity at each positive and negative zero crossover is typical of a circuit with rectification (guessing diodes in the excitation winding) . Although the voltage waveform is at zero at crossover point, current will still be flowing through a diode and it doesn't "want" to stop immediately. Eventually though the current does stop quite abruptly, so the magnetic field producing the voltage waveform dips, hence the little blips. This suggest both that the diodes are working and that if it uses only a single excitation winding, it has not gone open circuit.
[2] Purple arrow. Voltage has stopped increasing sinusoidally, magnetic field must not be increasing as normal. The field is made up of two parts and much of it is produced by the excitation winding, so very likely not enough current flowing in this winding. But you have already tried another AVR and it doesn't look like the winding is open circuit. Is there a capacitor associated with the excitation winding that is not in the avr circuit you swapped out ? They often have one in series with one, or sometimes two, excitation windings. Alternatively, shorted turns in the winding would lead to early saturation of the magnetic field and give that flat top to the sinusoid - but if that was the problem, I can't think why it would build up in that non linear manner.
