I was trying to repair a 550 W Honda petrol generator today. It's about 20 years old, and has 12 V dc and 240 V ac outputs.
I found that both output voltages were really low (about 8 V / 135 V) so I had a look inside the alternator. All the stator windings seem to be about the same thickness, which was a bit of a surprise, as I thought that the 240 V windings would need many turns.
What's really odd was the rotor. It seems to be 2 poles, with a separate winding on each pole. The rotor windings connect to a couple of axial components. There are no brushes or sliprings. Most of the rotor is laminated with a small permanent magnet set in the laminations at one end of the alternator.
The alternator voltage is very dependent on motor speed, and it turned out that the low voltage was due to it running slightly slower than it should have. When I increased the motor speed a little bit, the voltage came up to what it should be.
Does anyone know how this sort of generator / regulator works?
I found that both output voltages were really low (about 8 V / 135 V) so I had a look inside the alternator. All the stator windings seem to be about the same thickness, which was a bit of a surprise, as I thought that the 240 V windings would need many turns.
What's really odd was the rotor. It seems to be 2 poles, with a separate winding on each pole. The rotor windings connect to a couple of axial components. There are no brushes or sliprings. Most of the rotor is laminated with a small permanent magnet set in the laminations at one end of the alternator.
The alternator voltage is very dependent on motor speed, and it turned out that the low voltage was due to it running slightly slower than it should have. When I increased the motor speed a little bit, the voltage came up to what it should be.
Does anyone know how this sort of generator / regulator works?