The regulator isn't like an ordinary voltage regulator - 7812 etc - it works by controlling the current in the field winding, so controls the actual voltage generated. The maximum voltage with the field hard on would still depend on the load.
There's not actually that much difference in efficiency between a dynamo and alternator when both are at peak efficiency speeds. The advantage of the alternator is the slip rings carry only low current whereas the dynamo has the full output going through the brushes/commutator, so the alternator can be run at higher RPM. It's also easier to balance an alternator for high RPM. On an engine with a restricted rev range, like some diesels, there might not be much advantage in one over the other. But I'd guess an alternator is cheaper to make these days. A dynamo can be much improved with a solid state regulator over the old electro-mechanical type.
Sorry to nit-pick, but many British cars of the 50's and 60's used a 2-coil regulator which only had voltage control. Later cars, and those a bit more upmarket, used a 3-coil regulator giving voltage and current control.
Chris
I wasn't aware of that. I presume these generators were very conservative in their output, so that destructive currents weren't possible.
I've seen what happens to an armature when a Bosch regulator set for 38 amp maximum current is used to replace one correctly rated at 30 amp max.
John
They relied on the maximum load from the car electrics being less than their rated maximum output. Snag arose when people fitted spots etc and used them for long periods at high speeds. An alternator is inherently self regulating as regards maximum output due to the resistance of the diodes, etc.
Yes, they were theoretically rated at 22A, but in practice would never go above about 17A.
:-)
Chris
I've only got one workshop manual left that deals with a dynamo equipped car, and it's a Spridget one. The output of the C39 fitted to early 948 Spridgets is stated as 19 amps. ;-)
The C40 fitted to later cars is 22 amps.
Agreed. I'm not talking about increasing the speed. But the voltage is adjustable from the regulator and for a 50s car with no extras fitted a dynamo should be good enough if it is working properly.
John.
Adjusting the voltage can only be taken so far. And although you'd think an old car with no extras might be ok, modern driving conditions are very different. For example, headlights are now used at all times when dark - not so in the '50s in towns. So prolonged traffic jams with the headlights on can result in a flat battery.
MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.