Electronics > Projects, Designs, and Technical Stuff
Do modern car/boat alternators use PFC circuits?
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Circlotron:

--- Quote from: soldar on July 25, 2019, 04:06:10 pm ---PFC circuits exist in devices connected to the mains because the energy (current) has to be transported hundreds or thousands of Km from generation to consumption and PFC provides a reduction in power wasted in transmission.

In a car it makes no sense.

--- End quote ---
With a transformer driving a bridge rectifier and capacitive input filter you can only get about 60% of the transformer VA rating as DC Watts. Might be the same situation with a sine wave output alternator. PFC= more DC watts for the same AC VAs.
Circlotron:
Some time ago I put a scope on a car alternator winding. Was completely unloaded and on a test bench. The winding voltage was a sine wave of sorts but with fairly flattened peaks. This would broaden the conduction angle and reduce the current peaks, presumably with a better power factor than if it were a normal peaky sine wave.

The claws on the rotor are triangular and the air gaps between the claws are as a consequence skewed. Maybe these skewed air gaps introduce the flux into the stator in a more gradual and constant manner and that way produce the flattened top sine wave?
soldar:

--- Quote from: Circlotron on July 26, 2019, 07:34:36 am --- With a transformer driving a bridge rectifier and capacitive input filter you can only get about 60% of the transformer VA rating as DC Watts. Might be the same situation with a sine wave output alternator. PFC= more DC watts for the same AC VAs.
--- End quote ---
That's my point. With transmission lines being hundreds of Km long and including transformers along the way you want to optimize the power factor of the load.

With a car alternator it seems more simple and reliable to oversize it than to include electronics which are more prone to problems. If my car has a 100 amp alternator and I need more it is simpler to install a bigger alternator than to add a bunch of electronics which will still waste some energy in the form of heat.
mikerj:

--- Quote from: duak on July 26, 2019, 04:17:47 am ---Which vehicles have belt start engines?  Do they have a conventional starter too?

--- End quote ---

The second generation Smart ForTwo (451) had a belt drive starter/alternator and no conventional starter motor.  It is very problematic on this model, the belt is quite narrow and under a lot of tension and the high forces on the alternator/starter mountings cause the holes to elongate and the resulting misalignment causes the belt to wear and snap.  The same belt drives the coolant pump, so plenty of these cars have died with badly overheated engines.
Circlotron:

--- Quote from: duak on July 26, 2019, 04:17:47 am ---Which vehicles have belt start engines?  Do they have a conventional starter too?

--- End quote ---
Haflingers had a combined generator/starter/cooling fan that started the engine through the belt. Called a dynastarter. My uncle had one back in '69-'70.
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