Re: [A/S] Re: Generator -- Alternator vs Magneto??

[Mike Keith <mkeith@xxxxxxxxxxxx>]

George,

In a way, yes you are mixed up.  An automotive alternator produces 
Alternating Current (AC) and an Automotive generator produces DC 
Current.  The Auto Alternator changes the AC to DC internally through a set 
of diodes so there is DC coming out of the unit.  The advantage to 
alternators is that they produce higher charge currents at lower speeds. 
Remember back to the pre mid sixties cars, when you were driving at night 
and came to a stop the lights got real yellow, that is because they were 
depending on the battery alone, a generator starts it's charging around 
2000 RPM.  The downside to Alternators (and the upside to generators) is 
that the alternator will not charge a dead battery, the field in the 
alternator swaps places while the unit is running so there has to be a 
source of voltage to start the unit.  The generator on the other hand has a 
permanent magnet that provides the field.

The units we use to provide power to out trailers and motor homes are 
improperly called generators.  Technically the should be called ac power 
plants, but I don't see people changing their ways at this point.

Most small AC power plants run at 3600 RPM to produce 115 volts. This is 
because 60 Hertz (cycles per second) times 60 seconds in a minute is 3600 
hence the number of RPM require to get the right "frequency" so your 
appliances will work correctly and at the right temperature. These units 
are known as two pole alternators.

  Some higher end Power units run at 1800 RPM and still produce the correct 
voltage and frequency, they have two additional poles to provide the extra 
30 hertz.  These are 4 Pole units.

If I understand the small Honda and Yamaha power plants correctly, they are 
small DC producing units that have an inverter circuit to provide AC.  That 
would explain why they can run at slow speeds and still produce AC.

This is more than likely more than you wanted to know, but I hope it helps.

Mike